Theses and Dissertations

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Open Access
Development of a multi-breed heifer pregnancy genetic evaluation in beef cattle
(Colorado State University. Libraries, 2024) Giess, Lane Kurtis, author; Enns, R. Mark, advisor; Speidel, Scott E., advisor; Doyle, S. Patrick, committee member; Koontz, Stephen R., committee member
Heifer fertility represents a primary influence on the profitability of a beef cow-calf enterprise. Reproductive rates determine the number of calves born and thus influence the amount of beef product produced at the commercial level driving income for cow-calf operators. Heifer fertility then is an economically relevant trait, though in most cases pregnancy data are cumbersome, untimely to collect, and are considered a rare phenotype in national cattle evaluations (NCE). Despite this, there are successful examples of existing evaluations for heifer pregnancy (HP) across several beef breed associations. These HP genetic evaluations typically rely on categorical exposure (1 = exposed; 0 = not exposed) and pregnancy outcome (1 = pregnant; 0 = not pregnant) data and involve the use of threshold animal models (TM) to convert these binary observations to an underlying normally distributed range of values known as liabilities. These liabilities are then expressed as a percentage that predicts the likelihood of a bull's daughters becoming pregnant and giving birth as two-year-olds in the form of an expected progeny difference (EPD). However, despite these existing HP genetic evaluations, little improvement in the genetic trends in HP has been observed. Perhaps the reason for meager improvement in genetic trend is seedstock producers are not placing enough emphasis on HP, or with pregnancy rates already at or near 90% there is an assumption there is no need for genetic improvement. Additionally, though TM have been successfully implemented in genetic evaluations of HP, a common challenge with the methodology is the inability to evaluate data from contemporary groups that all have the same observation. Even more important is that TM are not supported in some software used for single-step genomic evaluation, such as BOLT by Theta Solutions. Because of these challenges, this study investigated the development of a multi-breed genetic evaluation for HP by performing a series of HP evaluations using TM, linear animal model (LM), and random regression model (RRM) methods. This study used HP data collected on heifers from 1974 to 2020 provided by the International Genetic Solutions (IGS) genetic evaluation, sourced from 9 partner breed associations. Because each breed organization may have its own nuanced definition of HP or differences in how data are reported, inconsistencies in HP data need to be investigated. For example, the American Simmental Association (ASA) does not have an upload format for producers to report HP data but instead uses a system of logic converting whole herd reporting (WHR) codes into HP phenotypes. The first study described the framework for how the ASA converted productivity, culling, and enrollment codes into HP phenotypes. It then evaluated the relative proportions of reasons why heifers/cows were culled. The proportion of heifers culled due to reproductive failure using this method of establishing HP phenotypes was 14%, which is consistent with the national average. The summary statistics for HP observations were cohesive with other HP observations reported to IGS partner breed organizations. Evaluating the effectiveness of these created phenotypes were investigated in the second study. Using data from the American Gelbvieh Association, the Red Angus Association of America, the North American Limousin Foundation, the American Shorthorn Association, and the Canadian Limousin Association, the second study estimated variance components, breed effects, and heterosis effects using LM and TM evaluation methods. Evaluations of HP were performed first within breed before a multibreed population was developed. The average heritability estimate across evaluations performed on 7 different breed groups for HP using LM methods was 0.026, with a minimum value of 0 and a maximum of 0.084. The average heritability for HP using TM methods was 0.17, with a minimum of 0.07 and a maximum of 0.28. Breed populations were then combined into a single multi-breed population, and the same stepwise procedure of incorporating heterosis and breed effects as fixed effects was used to generate variance components and fixed effect solutions. The heritability estimates in this multi-breed population were 0.023 and 0.088 using LM and TM methods, respectively. Heritability estimates did not change as additional fixed effects of breed and heterosis were fit. There were no statistically meaningful breed effects; however, heterosis results in a 17.2% increase (P<0.05) in the probability of HP when maximum heterosis is achieved. Results from this statistical method suggested that LM and TM may be performing equivalently for estimating HP breeding values in within-breed populations; however, in a multi-breed population, results were inconsistent, suggesting perhaps the model was over-specified with breed effects. These results suggest that LM as the model type within a genetic evaluation may be an alternative evaluation method for HP due to its simplicity, ability to use all available information, and support in modern genetic evaluation software programs. Due to being relatively simple to collect and economically important for beef producers, the third study performed a series of evaluations for age at first calving (AFC), which also served as an important investigation as AFC was a potential age covariate in HP evaluations. Models were implemented using single-breed populations and then combined into a larger multi-breed population so heterosis and breed effects could be estimated. The heritability estimates of AFC for Simmental and Red Angus were 0.19 ± 0.01 and 0.14 ± 0.01, respectively. These results demonstrate AFC in days is lowly to moderately heritable. However, when evaluating the genetic trend for both breeds the results seemed incongruous as AFC was sharply increasing over time. Many beef producers mass mate heifers at a single fixed breeding date. As a result, older heifers in a CG will not have the ability to have a younger AFC compared their younger counterparts in the same CG if conception occurs on the same day. To account for this systematic management influence which may be creating a disadvantage in some heifers, age differential (DIFF) was included to account for age differences prior to first exposure and was defined as the difference in days between an individual's birth date and the earliest birth date of an animal in a defined contemporary group. In addition to including DIFF as a fixed effect, accounting for heifer body weight prior to breeding was also considered, and subsequent bivariate animal models of AFC that included yearling weight (YW) were performed. Two bivariate multi-trait animal models for AFC and YW with random additive genetic and residual effects and fixed effects of contemporary group, breed proportion, and retained hybrid vigor were used. When DIFF was not included as a fixed effect, the additive, residual, and phenotypic variances for AFC were 126.1, 456.8, and 582.9 d2, respectively, and the genetic correlation between AFC and YW was 0.36 ± 0.02. When DIFF was included as a fixed effect, the additive, residual, and phenotypic variances for AFC were 10.0, 326.0, and 336.0 d2, respectively. The genetic correlation between AFC and YW was 0.19 ± 0.04. In the absence of DIFF, the heritability estimates for AFC and YW were 0.22 ± 0.01 and 0.44 ± 0.01, respectively, but were 0.03 ± 0.003 and 0.44 ± 0.01 respectively, when DIFF was included. Age differential had a significant effect on AFC at –0.86 (P < 0.0001). The low additive genetic variance of AFC, when accounting for DIFF, suggests that the influence of a female's age going into a fixed breeding date explains much of the variation in AFC. Because of the potential drawbacks associated with LM and TM evaluations of HP, the fourth study investigated alternative definitions of HP using RRM evaluation methods. Two fertility traits evaluated using RRM were proposed; the first being the evaluation of heifer pregnancy by calving week (HPcw), which regresses a binary calving event on the week a heifer calved within her contemporary groups calving window, and the second being the linear evaluation of binary HP which regresses HP on an age covariate such as age at first exposure (AFE) or yearling age (YAGE). In all evaluation methods, Legendre polynomials were used as the base function and observed heritability estimates at different age ranges were transformed from the (co)variances estimated for the intercept and linear term of HPcw or HP. Within the HPcw evaluations, two separate age covariates were proposed as additional fixed effects, with the first being age at first calving (AFC), and the second being AFE. Heritability estimates for HPcw fitting AFC as a fixed effect ranged from 0.39 to 0.56, though this is assuredly from AFC being a biased age estimate. Observed heritability estimates for HPcw across 10 weeks, fitting AFE as a fixed effect ranged from 0.010 to 0.20, which are more realistic and consistent with literature estimates compared to observed HPcw heritability estimates fitting AFC as an age covariate. For the HP evaluation regressing HP on YAGE, heritability estimates ranged from 0.01 to 0.14, suggesting that up to 14% of the variation in HP across ages could be attributed to differences in additive genetics. For the evaluation regressing HP on AFE, heritability estimates were 0 or near zero, so this evaluation method likely requires additional scrutiny. Differences in heifer age covariate and trait definition for the evaluation of HP provided expanded opportunities for the development of national cattle evaluations using RRM. The potential advantages of utilizing RRM in evaluations of categorical or single observation data are that it allows the use of all available data in a dataset and is more adapted to single-step genomic evaluation software systems. Because of this, RRM may be the preferred evaluation method for HP or related fertility traits, though this requires additional testing in global databases. Results from previous studies suggest there are options for evaluating HP in a multi-breed NCE, but no single method is ideal. While LM evaluations validate well, there is low variance in the EBV for the populations evaluated due to low heritability. The TM evaluations validate well and have reasonable predictions, but they cannot appropriately utilize all available data and are not supported by some modern genetic evaluation software programs. The potential of RRM evaluation methods is evident; however, further testing of this methodology must be performed before this approach can be considered.
Open Access
Exploration of bison industry practices and mitochondrial metabolism
(Colorado State University. Libraries, 2024) Velazco, David, author; Nair, Mahesh, advisor; Edwards-Callaway, Lily, advisor; Hess, Ann, committee member; Engle, Terry, committee member
The objectives of this study were to benchmark the United States bison meat industry and to compare the mitochondrial metabolism of beef and bison. The first project evaluated bison industry stakeholder perceptions on management, animal welfare, and meat quality with in-person and online surveys. The stakeholder surveys identified animal handling, bison behavior, employee training, facility design, and transportation duration as the most critical factors that could impact animal welfare in the bison production system. The stakeholders understood that animal welfare is a crucial component of bison production and directly affects meat quality. The second project analyzed multiple live animal factors to benchmark their influence on specific meat quality attributes. Live animal production parameters of bison (n = 2,284; Bulls n = 1,101; Cows n = 199; Heifers n = 984) such as distance traveled, season, number of head bumps in the chute, sex class, and live weight were associated (P < 0.05) with differences in fat thickness, ribeye area, blood splash presence, and instrumental color of bison meat. The third experiment compared the mitochondrial metabolism of bison and beef. The left side masseter muscle of crossbred Angus steers (n = 12) and bison (n = 12) were collected within 60 minutes postmortem. The oxygen consumption rate of permeabilized muscle fibers at specific respiration states was evaluated utilizing the Oroboros O2K high-resolution respirometry system. The abundance of electron transport chain protein in bison and beef muscle was measured using gel electrophoresis. All mitochondrial data were analyzed as mixed models with species as the fixed effect, and day confounded with sex class as the random effect, using JMP Pro 16. No differences were found in oxygen consumption flux (JO2) between bison and beef under baseline, Leak respiration (LEAK; P = 0.8813), rotenone respiration (ROT; P = 0.1071), and carbonyl cyanide m-chlorophenyl hydrazone respiration (CCCP; P = 0.7502) respiration states. Bison permeabilized muscle fibers had a higher (P = 0.0016) JO2 during max OXPHOS (+D) and produced more hydrogen peroxide (P = 0.0234) during this respiration state compared to beef. Respiration control rate (RCR) did not differ (P =0.2928) between beef and bison permeabilized muscle samples. Bison muscle samples contained lower relative abundance of the electron transport chain complexes II (P = 0.0057) and III proteins (P = 0.0020) than beef. Additionally, bison and beef had similar concentrations of citrate synthase in the masseter muscle (P = 0.4650). Results from these experiments can be used as an industry reference to monitor improvements in bison animal welfare and meat quality. Additionally, information regarding mitochondrial metabolism can serve as the foundation for future research to further investigate differences in efficiency between bison and beef.
Open Access
The effect of trace mineral source on solubility, rumen fermentation characteristics, and trace mineral concentration in protozoa and bacteria of steers consuming a lactation dairy type diet
(Colorado State University. Libraries, 2024) Loh, Huey Yi, author; Engle, Terry, advisor; Narayanan Nair, Mahesh, committee member; Coleman, Stephen, committee member; Torres-Henderson, Camille, committee member
A series of experiments were conducted to investigate the influence of trace mineral (TM) source on TM solubility, rumen fermentation characteristics, and trace mineral concentration in protozoa and bacteria of steer consuming a lactation dairy-type diet. Experiments 3 and 4 were classified as experiments 1 and 2 in chapter 3 for publication purposes in academic journal. In the first experiment, hydroxychloride TM (HTM) and sulfate TM (STM) sources of Cu, Mn, and Zn (n = 4/element/source; N = 24) were incubated separately in water for 24 h. Initial pH was measured after adding the TM to the solution, then the tubes were incubated at 39°C with agitation. After a 24-h incubation, samples were filtered to obtain the filtrate for TM analysis, and final pH readings were taken. Initial pH of each solution was greater (P < 0.03) for HTM compared to STM for all elements. Final pH tended to be greater for Cu (P = 0.09) and Zn (P = 0.07) from HTM compared to STM. Water solubility of Cu, Mn, and Zn from STM was greater (P < 0.01) than HTM sources. These data indicate that TM source influences pH and solubility of Cu, Mn, and Zn in water. In Experiment 2, eight steers fitted with rumen cannula were blocked by body weight and randomly assigned to treatments consisting of 10 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either STM or HTM sources (n = 4/treatment). Steers were individually fed a cracked corn-corn silage-based diet. Treatments were top-dressed daily. Rumen contents were collected at 0, 2, and 4 h post-feeding on d 1 and 14. On d 15, strained ruminal fluid (SRF) and particle-associated microorganisms (PAO) were obtained. Digesta from HTM-supplemented steers has a lesser (P < 0.01) Mn concentration than STM-supplemented steers on d 14 of the trial. Steers supplemented with STM had a greater (P = 0.0016) soluble Cu concentration in the rumen on d 14 than those fed HTM. Zinc was more tightly bound (P = 0.01) to the digesta in HTM-supplemented steers compared to STM on d 14. The data suggest that dietary TM source can affect rumen soluble Cu concentrations and binding strength of Zn to solid digesta. In Experiment 3, three cannulated steers were adapted to a diet formulated to meet the nutrient requirements for lactating dairy cows. Strained RF was obtained by straining rumen content through 2 layers of cheesecloth. Half of the remaining digesta was washed with McDougall's buffer and filtered through 2 layers of cheesecloth to obtain PAO. Both SRF and PAO were filtered again through 8 layers of cheesecloth. Strained RF was mixed with either McDougall's buffer (SRF) or PAO (SRF+PAO) at a ratio of 1:2 or 1:4 and incubated at 39°C for 12 h using the ground basal diet as the substrate. Digestibility of DM was greater (P < 0.05) in digestion tubes containing SRF and SRF+PAO at a 1:2 ratio. In Experiment 4, eight steers fitted with ruminal cannula were blocked by body weight and assigned to one of two treatment groups. Treatments consisted of 10 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either 1) sulfate (STM) or 2) hydroxychloride (HTM) sources. Steers were housed in individual pens and fed the same diet as described in experiment 1. Dietary TM treatments were mixed with dried distillers grains and mixed in the diet by hand, immediately after basal diet delivery. Dietary treatments were fed for 14 d. On day 15, SRF+PAO was collected from each steer (STM-RF and HTM-RF) and used in a series of in vitro crossover experiments. In vitro substrates (S) used were the ground diets consumed by the animals on each treatment (STM-S and HTM-S). Incubations containing HTM-S had greater (P < 0.01) total VFA concentration and propionic acid molar proportions, but lesser (P < 0.01) acetic acid molar proportions than STM-S. Rumen fluid from steers supplemented with HTM had a greater (P < 0.03) total VFA than STM-RF at 24h post incubation. After 12 h post incubation, the molar proportion of propionic acid in HTM-RF was lesser (P = 0.04) than STM-RF. After simulated abomasal digestion, soluble Mn concentration in HTM-S was greater (P < 0.01) than STM-S. These data indicate that the source of trace minerals can influence in vitro rumen fermentation characteristics and Mn solubility under simulated abomasal conditions.
Open Access
The effects of long-term molybdenum exposure in drinking water on molybdenum metabolism and production performance of beef cattle consuming a high forage diet
(Colorado State University. Libraries, 2024) Thorndyke, Meghan, author; Engle, Terry, advisor; Ahola, Jason, committee member; Edwards-Callaway, Lily, committee member; Holt, Timothy, committee member
In the current series of experiments the influence of long term molybdenum (Mo) exposure in the feed or water on copper (Cu) status, metabolic, reproductive, and carcass characteristics was investigated. The objective of experiment 1 was to conduct a life-cycle production and health assessment of lactating and gestating beef cattle, and their calves, exposed to varying doses of Mo. In this experiment Commercial, multiparous beef cows (n=54 in year 1; n= 51 in year 2) with calves (approximately 2 months of age) were used to evaluate the effects of Mo source (feed or water) on reproduction, mineral status, and performance in cows and calves receiving a grass hay diet [dry matter (DM) basis: 6.6% crude protein; 0.15% S, 6.7 mg Cu/kg, 2.4 mg Mo/kg] for 553 d. Cows were stratified by age, body weight (BW), and liver Cu and Mo status, and were then randomly assigned to one of six treatment groups. Treatments were: 1) Negative control (NC; basal diet with no supplemental Mo or Cu); 2) Positive control (PC: NC + Cu; 3 mg of supplemental Cu/kg diet DM from CuSO4·5H2O); 3) NC + 500 µg Mo/L from Na2MoO4·2H2O supplied in drinking water (Mo 500-water); 4) NC + 1000 µg Mo/L of Na2MoO4·2H2O supplied in drinking water (Mo 1000-water); 5) NC + Mo 1000-water + 3 mg of supplemental Cu/kg diet DM from CuSO4·5H2O (Mo 1000-water+Cu); and 6) NC + 3.0 mg of supplemental Mo/kg diet DM from Na2MoO4·2H2O (3.0 Mo-diet). During the winter months, animals were housed in three replicate pens per treatment and during the summer months animals were housed in separate pastures by treatment. Animals were allowed ad libitum access to both feed and water throughout the experiment. Cows were bred via artificial insemination during the summer months of both years of the experiment and calves were weaned at approximately 6 months of age in the fall of both years. All cows and calves were weighed, bled, and feed and water intake were determined every 28d. Cattle receiving diets containing less than 10 mg Cu/kg DM total diet became Cu deficient over the course of the experiment as determined by liver and plasma Cu concentrations. However, no Mo toxicity or Cu deficiency signs (e.g., reduction in growth rates, reproductive performance, or immune function) were observed throughout the course of the experiment for any treatment. Results suggest that Mo supplemented in water or feed at concentrations used in this experiment had minimal impact on Cu status and overall animal performance. However, dietary Cu concentration below 10.0 mg Cu/kg DM total diet reduced liver and plasma Cu concentrations to values indicative of a marginal Cu deficiency in beef cows. The objective of the chapter 3 review was to examine the impact of Mo in drinking water on cattle performance and Mo and Cu metabolism. The majority of Mo research has focused on the antagonist effect of Mo, alone or in combination with elevated dietary S, on Cu absorption and metabolism in ruminants. Diets containing both >5.0 mg of Mo/kg DM and >0.33% S have been reported to reduce the Cu status in cattle and sheep. Therefore, due to the potential for inducing Cu deficiency, Mo and S concentrations in the diet should be monitored and kept within appropriate values. Elevated sulfate concentrations in drinking water can also be detrimental to livestock production, especially in ruminants. High concentrations of sulfate in water have been extensively studied in cattle because high-sulfate water induces polioencephalomalacia in ruminants. However, little research has been conducted investigating the impact of Mo in water on Cu metabolism in ruminants. Based on the limited number of published experiments, it appears that Mo in drinking water may have a lower antagonistic impact on the cu status in cattle when compared to Mo consumed in the diet. This response may be due to a certain percentage of water bypassing the rumen when consumed by ruminants. The chapter 4 experiment objective was to of this experiment was to investigate the influence of prolonged exposure to elevated Mo water concentrations on apparent absorption and retention of both Cu and Mo in pregnant multiparous beef cows. In this experiment twelve multiparous beef cows of similar BW, age, and gestational length, from a larger cow-calf study, were utilized to evaluate the effects of molybdenum (Mo) consumption method (feed or water) on apparent absorption and retention of copper (Cu) and Mo. Cows (n=54) with calves had been assigned to one of six dietary and/or water treatments (n=9 cow-calf pairs per treatment) 301 d prior to selecting a sub-group of 12 cows. Treatments consisted of: 1) negative control (control; basal diet with no supplemental Mo or Cu), 2) positive control (control + 3 mg of supplemental Cu/kg DM), 3) control + 500 µg Mo/L from Na2MoO4·2H2O supplied in drinking water, (4) control + 1000 µg Mo/L of Na2MoO4·2H2O supplied in drinking water, (5) positive control + 1000 µg Mo/L of Na2MoO4·2H2O supplied in drinking water, and (6) control + 3.0 mg of supplemental Mo/kg diet DM from Na2MoO4·2H2O. The sub-group of cows were individually fed a low quality grass hay diet with their respective treatments, n=2 cows/treatment) for 14 d. On day 15, dry matter intake (DMI) was held at 90% of the group's average intake. Total fecal and urine output were then collected for 3 d. Dry matter digestibility and water intake were similar across treatments. Copper intake and apparent absorption and retention of Cu were greater (p < 0.05) in cows receiving supplemental Cu when compared to non-Cu supplemented cows. Apparent absorption of Mo was similar across all treatments. Apparent retention of Mo was greater while apparent absorption of Cu was lesser (p < 0.05) in cows receiving 3 mg of Mo/kg dm and cows receiving 1000 µg Mo/L when compared to all other treatments. These data indicate that Mo source (feed vs water) may impact apparent absorption of Cu in cows receiving a low quality forage diet. The chapter 5 survey of central Rocky Mountain livestock producers objective was to understand the mineral consumption within the forage and water as well as Cu and Mo status of the grazing cattle. Commercial, multiparous, crossbred beef cows from 3 independent cow-calf production operations were selected to assess the molybdenum (Mo) and copper (Cu) status of cattle raised in the Rocky Mountains. Fifteen cows from each operation were selected at random, during early summer and late fall processing. At the time of cattle processing, both jugular venipuncture blood samples and liver biopsies were obtained from each cow. Furthermore, all diet components, forage, water, and supplement samples were obtained from each location. Plasma, liver, water, and feed samples were analyzed for Mo and Cu concentrations via inductively coupled plasma mass spectrometry. Feed samples were also analyzed for moisture, crude protein (CP), ash, ADF and NDF. Water samples were sent to an established laboratory for general water quality analysis. On average, in the current survey forages samples contained 55.61% DM, 8.37% CP, 34.91% ADF, and 54.98 NDF with a Cu:Mo ratio of 2.8:1. Additionally, the water quality of the samples obtained were well within the "safe and should pose no health problems" category for beef cattle. Plasma Mo concentrations of 0.22 (±0.10) mg/kg DM were considered to be elevated in 64% of all samples obtained, likely a result of the elevated Mo forage concentrations in the grazed plant material. Plasma Cu of 0.83 (±0.11) concentrations were within normal ranges for all samples obtained. Molybdenum and Cu liver concentrations of 3.74 (±1.29) and 82.54 (±22.76) respectively, were within ranges considered to be normal for beef cattle for all samples collected. Based on the results of this survey, Mo and Cu plasma and liver concentrations in Colorado cow-calf operations in the central Rocky Mountains were similar to Mo and Cu plasma and liver concentrations in Cu supplemented cows in the previously described 2-year Mo supplementation cow-calf experiment. Furthermore, these data suggest that Cu supplementation at NASEM (2016) recommended concentrations of 10 mg Cu/kg DM total diet (or greater) meets the animals dietary Cu requirement for cattle consuming forages sampled.
Open Access
Hempseed meal as an effective protein supplement for finishing wethers
(Colorado State University. Libraries, 2024) Butts, Mercer, author; Archibeque, Shawn, advisor; Dillon, Jasmine, advisor; Myrick, Chris, committee member
To address the needs of an increasing global population and decreased availability of arable land due to the continued expansion of monoculture farms for the use of feeding livestock, it is necessary that we begin to research more sustainable methods for feeding animals, and the people who consume them. This study aims to address those needs by presenting hempseed meal (HSM) as a protein alternative to more commercially available feeds such as soybean meal commonly used in finishing rations on animal feeding operations (AFOs) across the United States. To complete this task, forty Western White-Faced wethers were used in a completely randomized block design with 5 treatments. These treatments included diets formulated to be near isonitrogenous with 0%, 5%, 10%, 15%, or 20% of diet DM as hemp seed meal, primarily as a substitute for soybean meal. Wethers were fed the diets individually for 90 d, which was followed by a 5 d balance trial with a total collection of urine and feces. There were no differences in DM intake (P = 0.44) or N digestibility (P = 0.467) between treatments, although there was a slight increase in P digestibility as hemp meal inclusion increased until it represented 15% of the dietary DM (P = 0.047). There were no differences in urinary N excretion (P = 0.33) or urinary urea excretion (P = 0.34) between treatments.
Open Access
Liver abscess effects on carcass performance and heritability estimates of liver abscess incidence and severity in beef on dairy heifers
(Colorado State University. Libraries, 2024) Zuvich, Miranda Lee, author; Enns, R. Mark, advisor; Speidel, Scott E., advisor; Woerner, Dale, committee member; Holt, Timothy N., committee member
The economic impact of liver abscesses has been reported to be not only due to loss from condemnation of livers but also from impacts on performance. A primary focus in decreasing liver abscess prevalence has been on prevention methods because with limited or no clinical signs present, diagnosis of liver abscesses in live animals is complicated, and no prevention methods have been highly effective in mitigation. As a result, this study aimed to identify the impacts of liver abscesses on carcass performance and estimate heritability for liver abscess incidence and severity in fed beef on dairy heifers. In the first study, 1,860 beef on dairy heifers were fed and harvested in Kansas. All had phenotypes for hot carcass weight (HCW; kg), rib eye area (REA; cm2), fat thickness (FT; cm), marbling score (MS), calculated visual yield grade (VYG), and liver abscess score. Of the 1,860 individuals, 1,646 had phenotypes for heart score (HS). Carcass impacts were estimated using fixed effects of liver abscess score, contemporary group, and age in days. The contemporary group was a concatenation of kill lot and treatment. Liver abscess score was fit in two different forms: 6 scores ("0", "A-", "A", "A+", "A+AD", "A+O") and 4 scores ("0", "A-", "A", "A+") where "A+" included scores of "A+AD" and "A+O". A score of "0" indicated no abscess and abscess severity increases with "A-", "A", and "A+". The scores of "A+AD", and "A+O" indicate there is adhesion of the liver to nearby organs and ruptured abscess, respectively. A significant increase was identified using the six-score model for FT for animals with scores of "A+O" compared to "A+", with respective least-squares means of 1.94 cm ± 0.12 and 1.59 cm ± 0.06 (P < 0.05). While not significant, tendencies were identified for FT for animals with scores of "A" and "A+AD" compared to "A+O" (0.05 ≤ P < 0.1) with respective least-squares means of 1.61 cm ± 0.06, 1.61 cm ± 0.05, and 1.94 cm ± 0.12. A significant increase was identified using the six-score model for VYG in animals with VYG scores of "A+O" higher than "A+" and "A+AD", with respective least-squares means of 3.75 ± 0.19, 3.20 ± 0.09, and 3.20 ± 0.08 (P < 0.05). When using the 4-score system, HCW was significantly lower for animals with scores of "A+" compared to those with non-abscessed livers. Hot carcass weight least-squares means for animals with no abscesses was 396 kg ± 2.63, and for those with severe abscesses was 391 kg ± 2.92 (P < 0.05). In the second study, 1,492 beef on dairy heifers fed and harvested in Kansas had liver abscess scores and sire information. Nine models were utilized to estimate heritability, all with fixed effects of contemporary group, age in days, and number of bovine respiratory disease treatments. The contemporary group was a concatenation of kill lot and treatment. Models 1, 4, and 7 were from data sets with all sires represented but had liver abscess score represented as a continuous variable, a binary score indicating abscess presence, and a binary score indicating severe abscess ("A+") presence, respectively. Models 2, 5, and 8 followed the same respective scoring systems as Models 1, 4, and 7, but the data set only included heifers from sires with 10 or more progeny. Models 3, 6, and 9 followed the same respective scoring systems as Models 1, 4, and 7, but the data set only included heifers from sires with 100 to 200 progeny in the complete data set. Heritability estimates from a sire model for Models 1, 4, and 7 ranged from 4.26 x 10-8 to 1.06 x 10-7. Heritability estimates from a sire model for Models 2, 5, and 8 ranged from 4.90 x 10-8 to 4.61 x 10-7. Heritability estimates from a sire model for Models 3, 6, and 9 ranged from 1.01 x 10-7 to 2.88 x 10-3. All estimates indicate no genetic component to liver abscess severity or incidence in this data set.
Open Access
Management and benchmarking strategies to improve financial health status of U.S. beef operators
(Colorado State University. Libraries, 2024) Krehbiel, Bethany Cornwell, author; Rhoades, Ryan D., advisor; Ahola, Jason K., advisor; Blackburn, Harvey D., committee member; Mooney, Daniel, committee member
The objective of this dissertation was to obtain, analyze, and summarize historical Standardized Performance Analysis (SPA) benchmark information and subsequently determine significant Key Performance Indicators (KPI) influencing beef producer's Unit Cost of Production (UCOP). Using the KPI's, a Ranch Health Index (RHI) was developed to assist producers in simply analyzing their financial health while analyzing beef production and financial relationships. Lastly, producer information using the significant KPI's incorporated into the RHI was analyzed for sensitivity to explore potential leverage points to enhance overall financial health. The SPA Beef cattle production performance and financial data was obtained from the SPA program conducted by Texas A&M AgriLife Extension which has records from three states: Oklahoma, Texas, and New Mexico. The dataset contained 25 years of beef financial and production metrics from 1992 – 2016. Three models (linear regression, random forest, and step-wise) were used to assess the SPA data for KPI. Upon further analyses, six variables were considered most impactful to predict Unit Cost of Production: Financial Grazing per CWT, Financial Raised/Purchased Feed per CWT, Livestock Cost Basis per CWT, Weaning Pay Weight per CWT, Pounds Weaned, and Number of Adjusted Exposed Females. The RHI was developed from the six variables using a Random Forest machine learning model and their corresponding importance factors as weights in the model. The model selected was tested and showed concordance with all the SPA variables predicting UCOP. Therefore, the RHI results showed utility in usefulness to assess financial health. Subsequently, three producers with 5 consecutive years of data were tested for sensitivity at ± 5% and ± 10% from the original value to determine sensitivity of each KPI variable. Finally, the models were investigated for maximum and minimum RHI values. Results showed changes in RHI up to $13,000 when accounting for all KPI improvements at 10% sensitivity. In conclusion, knowledge of the SPA data and ultimately the RHI provides information to cattle producers on what may be the most indicative variables for enhanced profits. In addition, this research has provided a simple and effective way for producers to analyze their beef operation.
Open Access
Association between beef ribeye area measurements and steak portion size
(Colorado State University. Libraries, 2024) Schiefelbein, Abbey Faith, author; Nair, Mahesh N., advisor; Geornaras, Ifigenia, committee member; Clark, Daniel, committee member; Hess, Ann, committee member
As cattle weights have increased over the past decades, hot carcass weight and ribeye area (REA) have also increased. The REA is an important determinant of carcass value as it impacts the thickness of steaks when portioned to a pre-determined weight. Additionally, previous research has indicated that steak thickness impacts consumers' eating experience potentially due to its impact on the degree of doneness. The objective of this study was to examine the relationship between carcass REA and steak portion size. Beef carcasses (n = 100) were selected from a commercial beef harvesting facility based on REA in 1 in2 (6.45 cm2) increments ranging from less than 11 in2 (70.97 cm2) to greater than 19 in2 (122.58 cm2) based on a United States Department of Agriculture-approved camera (E+V) with 10 total categories. Data (hot carcass weight, back fat thickness, and marbling) were collected from each selected carcass. The REA measurements were obtained using the grading camera, a manual grid, and pen tracing and measured using ImageJ software. Strip loins (IMPS#180) from selected carcasses were collected, and weight, length, and three width (anterior, middle, and posterior) measurements of the strip loins were measured manually. Each strip loin was then scanned through a Marel I-Cut 56 portion cutter to determine the thickness of 12 oz (340.19 g) and 16 oz (453.59 g) portions and to determine the weight of a 1-in (2.54 cm) thick portion. To quantify and describe the relationship between steak thickness (cut to 12 oz and 16 oz portions) and steak weight (cut at 1-in. thickness), linear regression models were developed using traced REA as the independent variable. Additionally, more exhaustive linear regression models were developed to predict steak thickness or weight based on the traced REA, hot carcass weight, fat thickness, strip loin weight, strip loin length, strip loin width, and average maximum height of the strip loin. Each model was evaluated separately for the main effects of each variable, with significance determined at ɑ=0.05. There was a significant (P < 0.001) correlation and linear relationship (P < 0.05) between traced REA measurement and 12 oz (R2 = 0.71), 16 oz (R2 = 0.71), and 1-in.-thick (R2 = 0.75) portions examined in this study. For 12 oz steaks, the steak thickness decreased by an estimated 0.055 in. (0.14 cm) for every 1-in. increase in REA. Similarly, for the 16 oz steaks, the steak thickness decreased by an estimated 0.074 in. (0.19 cm) for every square in. increase in REA. The 1-in. steak portions had a mean weight of 340 g, and the steak weight increased an estimated 18 g for each square in. increase in REA. In addition, using the strip loin measurements, linear regression models were able to predict steak thickness for 12 oz and 16 oz portions with an R2 of 0.95 each and predict the steak weight for the 1-in. portion with an R2 of 0.98. As expected, REA strongly correlated with the portion size of strip loin steaks cut to a specified weight or thickness. Additionally, our results indicated that the weight and length of the strip loin were good predictors of steak thickness (for 12 oz and 16 oz portions) or steak weight (for 1-in.-thick portions). Further research exploring consumer acceptance and degree of doneness for steaks with varying thicknesses would provide data to determine REA ranges and targets that would optimize steak portion sizes and consumer acceptability.
Open Access
Effects of origin on enteric greenhouse gas emissions and growth performance
(Colorado State University. Libraries, 2024) Mesa Gandolfo, María Inés, author; Carvalho, Pedro H. V., advisor; Stackhouse-Lawson, Kim R., committee member; Place, Sara E., committee member; Ritten, John P., committee member
Methane (CH4) emissions from cattle across various origins remain inadequately understood, representing a significant knowledge gap for sustainable beef production. This study investigates enteric CH4 emissions from yearling steers of different origins and under different management practices. The experiment was divided into two phases. In Phase 1, steers were managed according to local practices: grazing in Colorado and confined background feeding in Nebraska and Wyoming. In Phase 2, all steers were moved to a common grazing environment in Colorado. Methane emissions were measured using the Automated Head Chamber System (AHCS). During Phase 1, CH4 emissions and growth performance varied significantly among the groups, influenced by diet and management. Nebraska steers had the greatest CH4 production (MP), while Colorado steers had the least, reflecting differences in diet composition and feed intake. However, CH4 intensity (MI) was similar across all groups due to compensatory differences in average daily gain (ADG). In Phase 2, when all steers grazed under the same conditions, Colorado steers exhibited the greatest ADG and MP, indicating better adaptation and suitability to the grazing system than Nebraska and Wyoming steers. Results suggest that enteric CH4 emissions are influenced by cattle's origin and previous management. This highlights the need for context-specific studies to accurately assess the sustainability and greenhouse gas (GHG) mitigation strategies for grazing beef cattle. Further research should address these variations to improve the accuracy of CH4 emissions estimates in different rangeland ecosystems. This study also evaluated different CH4 prediction equations using various statistical approaches (RMSE, R2, Mean and Slope bias, correlation coefficients, and least square differences). Three equations showed potential for predicting CH4 emissions for the steers of the current study: the one by Ellis et al. (2009), the one by Escobar-Bahamondes et al. (2016), and Moraes et al. (2014). Even though the CH4 estimated by these equations was similar to the observed, there is room for improvement in the development of accurate equations to predict cattle enteric CH4 emissions in grazing systems. Lastly, the animals were ranked in both Phases by their MI and MP, and it was evaluated if the animals changed their ranking in Phase 1 when moved to Phase 2. Animals from all origins experienced shifts in their classification categories, indicating the dynamic nature of CH4 across different contexts. However, it was observed that steers from the Wyoming group exhibited the most significant changes in MP classification categories when transitioning from a confinement system with grain-based diets to a grazing system. Based on the current results, the background of the steers may need to be considered when evaluating sustainability goals in beef cattle production systems.
Open Access
Pre-weaning performance in lambs after nutrient specific restriction in gestation and training cognitive skills to improve integration and application of knowledge in animal physiology
(Colorado State University. Libraries, 2024) Stucke, Rachael, author; Cadaret, Caitlin N., advisor; Ahola, Jason K., committee member; Winger, Quinton A., committee member
Due to seasonal availability and quality of range forage, extensively managed ewes often experience nutrient restriction during gestation. Neonatal lamb performance after severe experimental nutrient restriction during gestation has been well studied; however, there is a gap in understanding of how practical nutrient restriction experienced over the course of a production cycle impacts lamb success. Therefore, the objective of the first study was to investigate early life performance in lambs from ewes fed a diet from 30-125 days of gestation (dGA) that simulates winter forage or one that meets all nutritional requirements for gestation. Maternal BCS and weight losses were evident prior to the standard supplementation period suggesting impacts on the fetus could be happening due to nutrient restriction earlier in gestation. Lambs from dams who received the lower quality diet did not differ by bodyweight but were not able to thermoregulate as well as lambs whose dams had their requirements met during the first week and on specific weeks thereafter. Beginning at six weeks of life through weaning lambs from restricted dams had lower body weights compared to lambs from fully nourished dams. This data demonstrates that nutrient challenge during gestation, even when re-alimented in late gestation, decreases performance. The lamb data showed that while there are no apparent differences in growth during the first week of life, NR animals start to diverge later in life even when provided high quality nutrition. This coupled with reduced thermoregulatory ability suggests tissue specific differences may underlie animal variation and warrants further investigation. Case-based learning immerses students in real-world scenarios, prompting observation, action, and reflection to enhance cognitive skills. The open-ended nature of such learning can challenge students to reach higher levels of critical thinking, however, we have noticed that without guidance, students often do not know how to approach these types of questions. Therefore, the objective of study 2 was to investigate how two low-input interventions strategies may help train cognitive skills and improve student performance. Three semesters of an undergraduate physiology course employed a case-based assessment strategy. Semester 1 (S1) represented no intervention, Semester 2 (S2) included two dedicated class periods of instructor-led guidance on approaching case studies, and Semester 3 (S3) utilized an online peer evaluation platform, where students evaluated and provided feedback to each other. In S2 and S3 pre-surveys were administered to understand changes in students' perceptions of their own cognitive skills. The average grade on case studies after intervention was the highest in S3 where peer intervention was employed. When comparing changes in perceptions, student confidence in their cognitive skills generally increased in S2 and S3. Interestingly, while peer evaluation improved student performance, free response questions indicated that students did not enjoy peer evaluation and felt that it was not beneficial to their learning. Peer evaluation provides a unique opportunity for students to actively engage in the learning process and to practice cognitive skills. This process holds dual benefit as reviewing peers requires students to reflect, analyze, and evaluate, which are cognitive skills also needed to solve the case studies.
Embargo
Transposable elements and early pregnancy in the horse
(Colorado State University. Libraries, 2024) Southerland, Sierra L., author; Coleman, Stephen, advisor; Bruemmer, Jason, committee member; Fedorka, Carleigh, committee member; Pinedo, Pablo, committee member; Chicco, Adam, committee member
Understanding the molecular events and physiological dynamics in the endometrium during early pregnancy is crucial for improving our understanding of reproductive outcomes in horses. Much of the work investigating early pregnancy in the horse has focused on maternal recognition of pregnancy (MRP). This critical signal, which initiates the pathways and regulatory changes to help make the endometrium receptive to pregnancy, remains elusive in the horse. Transposable elements (TEs), once overlooked components of the genome, have been implicated in regulating gene expression during critical stages of embryo and placental development. The current study investigated the expression of TEs during the early phase of pregnancy post-ovulation. The hypothesis tested was that pregnancy status would impact the expression patterns of TE-derived transcripts in the endometrium around the time of maternal recognition. It was anticipated that the TE transcripts would increase in the endometrium of pregnant mares either in response to or as a part of the maternal recognition signal. RNA sequencing data was generated from endometrial biopsies at days 9, 11, and 13 in pregnant and non-pregnant mares. Bioinformatics analyses identified distinct patterns of TE expression across the duration of early pregnancy. Contrary to expectations, these findings did not reveal the accumulation of TE transcripts in the pregnant endometrium compared to the non-pregnant endometrium during early pregnancy. Instead, there was a significant decrease in the number of differentially expressed transcripts over the time points studied. These results challenge the initial assumption and suggest that the regulation of TE transcriptional activity during early pregnancy may be more complex than previously thought, highlighting the need for further research into the roles of TEs in equine reproductive physiology. An alternative explanation for the results of this analysis is that maternal recognition of pregnancy may involve the downregulation of transcripts expressed from TEs, potentially serving as a switch to prevent luteolysis and maintain pregnancy. This study underscores TEs as potential biomarkers and regulators in equine reproduction, providing insights into endometrial processes and offering avenues for improving fertility outcomes and breeding efficiency in horses.
Open Access
The association of lunar phases with pregnancy at first artificial insemination of dairy cows
(Colorado State University. Libraries, 2024) Schatte, Margaret, author; Grandin, Temple, advisor; Pinedo, Pablo, advisor; Keller, Kayleigh, committee member
Myths and old farming legends have circulated the belief that the full moon affects livestock behavior and reproduction. To assess this association in dairy cattle, 13,558 records from 2019 to 2021 at an organic dairy farm in Colorado were analyzed. These records included lactation number, artificial insemination date (AI date), and pregnancy result. AI date was categorized into season and lunar phases. Lunar phases were separated into four equal categorizations: new moon, first quarter, full moon, and third quarter. The primary objective of this study was to identify any associations between the lunar phases and PAI1 (pregnancy rate at first AI). The secondary objective of this study was to use logistic regression to specify which phases had the lowest and greatest PAI1 while accounting for other effects on fertility. Logistic regression was used to complete this by comparing the pregnancy result of lunar phases while accounting for lactation number and season, which are known to affect pregnancy rate. The 4 lunar phase categorizations did have an association on PAI1 (p<0.05). The new moon phase resulted in the lowest PAI1 at 35.3% while the third quarter was the highest at 38.3%. Estimated marginal means were explored to identify the seasonal effect on pregnancy and found that winter had the highest probability of pregnancy and summer had the lowest. This analysis of 3 years of records provides evidence that the week of the new moon is the least probable week out of the month for pregnancy after first AI to occur, while the week before and week of the full moon are the most probable days for pregnancy after first AI to occur within the lunar cycle.
Open Access
Influence of BOVAMINE DEFEND® Plus on growth performance, carcass characteristics, estimated dry matter digestibility, rumen fermentation characteristics, and immune function in finishing beef steers
(Colorado State University. Libraries, 2024) Miller, Alexandra C., author; Engle, Terry E., advisor; Edwards-Callaway, Lily, committee member; Holt, Timothy, committee member
One hundred and eighty crossbred beef steers (406.0 ± 2.2 kg) were used to determine the impact of a novel direct-fed microbial (DFM) on growth performance, carcass characteristics, rumen fermentation characteristics, and immune response in finishing beef cattle. Steers were blocked by body weight and randomly assigned, within block, to 1 of 2 treatments (3 replicates/treatment: 30 steers/replicate). Treatments included: 1) no DFM (control) and 2) DFM supplementation at 50 mg∙animal-1∙d-1 (BOVAMINE DEFEND® Plus). All steers were fed a high-concentrate finishing diet and individual feed intake was recorded daily via the GrowSafe® system. Body weights were collected every 28 d. On d 55, 10 steers per pen were injected with ovalbumin (OVA). Jugular blood samples were collected from each steer on d 0, 7, 14, and 21 post-injection. On d 112, the same steers were injected again with OVA and intramuscularly with a pig red blood cell solution. Jugular blood samples were collected from each steer on d 0, 7, 14, and 21 post-injection. On d 124 rumen fluid was collected from 3 steers per treatment and used to estimate in vitro rumen fermentation characteristics. Equal numbers of steers per treatment were transported to a commercial abattoir on d 145, 167, and 185 of the experiment, harvested, and carcass data collected. Initial body weight (BW) was similar across treatments. On d 28 and 55, steers receiving DFM had heavier BW (P < 0.01) compared to controls. Average daily gain was greater in DFM-supplemented steers from d 0 to 28 (P < 0.01) and d 0 to 55 (P < 0.01) of the experiment compared to controls. Overall dry matter intake was greater (P < 0.04) and overall feed efficiency was similar in DFM-supplemented steers compared to controls. Dressing percentage (P < 0.02) was greater in steers receiving DFM compared to controls. Antibody titers to injected antigens were similar across treatments. However, red blood cell superoxide dismutase activity was greater (P < 0.05) in DFM-supplemented steers compared to controls. In vitro molar proportions of isobutyric and butyric acid were greater (P < 0.01) and dry matter (DM) digestibility tended (P < 0.07) to be greater in rumen fluid obtained from steers supplemented with DFM. These data suggest that BOVAMINE DEFEND® Plus supplementation improves growth performance during the initial period of the finishing phase, increases overall dry matter intake and dressing percentage, and may impact antioxidant status in beef cattle.
Open Access
Effect of hot-iron brand size and meloxicam on behavior, health, and performance of beef calves in a pasture setting
(Colorado State University. Libraries, 2024) Keogh, Lily, author; Edwards-Callaway, Lily, advisor; Cramer, Catie, advisor; Wolfe, Barb, committee member; Engle, Terry, committee member
Animal welfare is of growing importance in beef cattle production and therefore there is heightened interest in regularly practiced, painful management practices. Hot-iron branding is a common method of permanent identification of cattle, created by intense thermal damage to the hide. The main objectives of the study were to quantify the effects of hot-iron brand size and meloxicam on pain related behaviors and health and performance parameters of 2-month-old beef calves on a commercial cow calf operation. A total of 126 calves were enrolled in the study (bulls, n=56; heifers, n=70). Calves were hot-iron branded with one of two iron sizes (small (SM), large (LG)) and administered meloxicam (MEL; dosed for a 113-kg calf at 1mg/kg of bodyweight) or a placebo (PLA)), and castrated (CAS) or not castrated (NCAS), if a heifer calf. Following the treatment application, behavioral observation (2 h periods) using instantaneous scan sampling occurred at 6 h and 24 h post branding; these observation periods (OP) represent the pharmacokinetics of oral meloxicam. A logistic regression (PROC GLIMIX) was used to assess the association between castration status, brand size, medication, observation period, as well as any interactions, on the proportional behavioral outcomes. More LG brand calves were observed standing, lying, and displaying event behaviors as compared to the SM brand calves (P = 0.003, P = 0.011, P = 0.016, respectively). OP affected the display of event and state behaviors, with standing observed more at 6 h and event behaviors displayed more at 24 h (P = 0.0028). Concurrently, CAS and SM or LG branded calves exhibited more event behaviors and standing than NCAS calves (P = 0.022). No effect of the fixed variables on average daily gain (ADG) or morbidity were observed (P > 0.05). MEL did reduce the proportion of branded heifer calves expressing event behaviors as compared to PLA, however it had less of a behavioral impact on the concurrently castrated and branded calves (P = 0.022). The results indicate that pain is present within the 24 h following branding and castration and that concurrent castration and branding elicits a greater behavioral response than only branding. This study highlighted both the feasibility of administering an oral analgesic in a commercial setting and that implementing a smaller brand size may be a strategy to reduce pain associated with hot-iron branding.
Open Access
Propionibacteriaium acidipropionici CP 88 dose alters in vivo and in vitro ruminal fermentation characteristics
(Colorado State University. Libraries, 2024) Levenson, Jonah, author; Engle, Terry E., advisor; Wagner, John J., committee member; Torres-Henderson, Camille, committee member
Twelve steers, fitted with rumen canulae were used in a 4 x 4 Latin square design to examine the impact of the direct fed microbial Propionibacteria acidipropionici (PA) on rumen fermentation characteristics. All steers were housed together in one pen equipped with GrowSafe feed intake monitoring stations and one Greenfeed system used to estimate in vivo methane production. Steers were fed a corn silage-based diet throughout the experiment. Treatments consisted of PA administered at: 1) 0.0; 2) 1.0 x 108; 3)1.0 x 109; and 4) 1.0 x 1010 CFU∙animal-1∙day-1. Treatments were administered directly into the rumen as a single bolus dose daily. On day 7 and 14 of each period, rumen fluid was collected from each steer 2 h post treatment administration for VFA analysis and for determining in vitro fermentation characteristics. Following a 14-d washout period, animal treatments were switched, and the experiment repeated. Data were analyzed as a 4 x 4 Latin square design. In vivo propionic acid molar proportions (25.4 vs 23.6±0.24 mM) and total VFA concentrations (125.2 vs 121.3±1.87 mM) were greater (P < 0.05) in steers receiving PA when compared to controls. In vitro DM disappearance (P < 0.05; 63.3% vs 59.2%±1.12) and total VFA (P < 0.05; 147.9 vs 145.2±1.76 mM) were greater and methane (ml/g DMD) lesser (P < 0.04; vs 13.1 vs 15.6±0.11) in fermentation vessels incubated with rumen fluid from animals receiving PA when compared to controls. Dry matter disappearance (P < 0.03) and propionic acid (P < 0.04) increased linearly as dose of PA increased. In vitro total VFA tended (P < 0.08) to increase linearly and methane production tended (P < 0.09) to decrease quadratically in response PA dose. In vivo methane production was similar across treatments. In conclusion, PA addition improved in vivo and in vitro rumen fermentation, gas production, and rumen microbial manipulation.
Open Access
Gene expression analysis before and after the pelvic flexure in the equine hindgut
(Colorado State University. Libraries, 2024) Moss, Cameron D., author; Coleman, Stephen J., advisor; Engle, Terry, committee member; Metcalf, Jessica, committee member; Landolt, Gabriele, committee member
The equine hindgut is the primary site of the horse's nutrient breakdown, absorption, and energy production. More than 60% of the horse's energy comes from hindgut fermentation. In this process, commensal microbes in the hindgut aid in the digestion of plant materials to create volatile fatty acids that can be used by host cells to make energy. Many severe health issues- such as colic, laminitis, or colonic impactions- often occur in the equine hindgut, making it an important site to study to provide better management, treatment, and prevention options for horses suffering from gastrointestinal disease. Although much research exists focusing on the microbiome and overall physiology of the equine hindgut, relatively little addresses the role of gene expression in maintaining a complex yet essential homeostatic balance within the gastrointestinal tract. Previous from our lab found major differences in the microbial content of gastrointestinal compartments of the equine hindgut, separated by the pelvic flexure. The pelvic flexure is a short, narrow, horseshoe-shaped loop in the equine large colon. It defines the ventral and dorsal segments of the colon and is a common site of colonic impaction in horses. Although the pelvic flexure cannot and should not act as a "barrier," something "barrier-like" may be occurring around this region as it pertains to the hindgut microbiome. The mechanism for this action is not defined. As a result, this thesis aims to investigate gene expression in the intestinal epithelial cells of the ventral colon, pelvic flexure, and dorsal colon regions of a healthy hindgut to determine what differences exist. The insight gained from this analysis will provide a baseline for comparison to understand how gene expression patterns in these tissues adapt to changes in the microbiome and external factors like diet. The results of this thesis are the first steps towards a better understanding of homeostasis in the equine hindgut.
Open Access
Use of video image analyses to identify carcass characteristics and sensory quality of beef products generated from mature cow carcasses
(Colorado State University. Libraries, 2009) Woerner, Dale R., author; Belk, Keith E., advisor; Tatum, J. Daryl, advisor
A single study (sponsored by the beef check-off) was conducted to investigate the ability of video image analysis technology to identify carcass characteristics and sensory attributes of products generated from mature cow carcasses. Market cows representing three pre-harvest management strategies were used to evaluate the ability of video image analysis (VIA) to identify the impacts of pre-harvest management (MGMT) on carcass muscle and beef sensory characteristics. Cow MGMT groups were as follows: (1) Non-fed cows (n = 104) (NON-FED; beef-type cows entering the slaughter facility as culls from sale barns and/or ranching operations); (2) Fed cows (n = 108) (FED; beef-type cows entering the slaughter facility from a finishing yard having received a corn-based, high energy diet for a 95 d ± 1 d period); (3) Dairy cows (n = 113) (DAIRY; cows entering the slaughter facility directly from dairies as culls). FED market cows were fatter, heavier, and more muscular than either NON-FED or DAIRY cows. DAIRY cows were slightly fatter (in the carcass), heavier, and less muscular (alive, muscle score) than were NON-FED beef cows. FED beef cows had the most desirable lean color scores, the most tender LM steaks, and had whiter colored fat than NON-FED beef cows. DAIRY cows were the most youthful (lowest SKELMAT and dentition scores) at the time of harvest and produced carcasses that had similar marbling and fat color scores to those of FED beef cow carcasses. NON-FED beef cows produced the lowest marbling scores, the toughest LM steaks, and the most yellow colored fat. Correspondingly, fat from NON-FED beef cows had the highest concentrations of vitamin A and 3-carotene in the fat. NON-FED cows had the greatest probability of producing beef with undesirable flavor attributes but no meaningful differences were found among MGMT groups in fatty acid composition. Cow LM representing all MGMT groups responded to postmortem muscle-aging (P < 0.001) whereas the PM did not (P = 0.075). A MGMT x postmortem muscle aging time interaction existed for the INFRA (P < 0.042). A significant interaction of MGMT x evaluation method (USDA grader vs. VIA instrument) existed for marbling score, LMA, and 12th rib fat thickness. Compared to USDA grader determined values, VIA instrument scores were higher for marbling score and lower for LMA. A prediction model developed from VIA instrument outputs demonstrated the ability to characterize the MGMT of cow with less than 13% error. The findings of this research warrant the continued development VIA instruments to identify cow carcass characteristics and sensory quality.
Open Access
Application of yeast technology in ruminant nutrition
(Colorado State University. Libraries, 2009) Swyers, Kelcey L., author; Archibeque, Shawn L., advisor
This research aimed to evaluate two types of yeast technology applications that are commercially available to feed in the diets of beef cattle; these two applications are dried distiller's grains with solubles (DDGS) and yeast culture (YC). First, DDGS were offered as a protein and energy supplement to pregnant range cows to evaluate performance, and nitrogen and trace mineral status of cows and calves (Exp. 1), then YC was fed as a natural alternative to an ionophore to heavy-weight yearling beef steers fed finishing diets consisting of 19.7% DDGS to evaluate growth performance, carcass merit, cost of gain (COG) (Exp. 2), and fecal prevalence of the foodborne pathogen, E. coli O157:H7 (Exp. 3). In Exp. 1, supplementing the diets of pregnant beef cows maintained on dormant winter range with DDGS improved cow performance, had limited impact on nitrogen or mineral status, and was more economical to feed than the control diet (standard range cubes). In Exp. 2, we found that feeding YC may improve carcass characteristics of steers finished at lower end weights, which could result in fewer days on feed; however, there was no advantage on growth performance or COG. Lastly, Exp. 3 indicated that feeding YC decreased, but did not eliminate, fecal shedding of E. coli O157:H7 upon initial application.
Open Access
Prevalence and control of Listeria, Salmonella and Escherichia coli O157:H7 in Colorado rural households
(Colorado State University. Libraries, 2009) Rodríguez Marval, Mawill R., author; Belk, Keith, advisor; Sofos, John, advisor
The household environment has been linked to multiple outbreaks of foodborne illnesses, including listeriosis and salmonellosis. The food handling habits of consumers play a critical role in the food chain continuum, and need to be investigated to better prevent foodborne illnesses that originate at home. The objective of this work was to identify risk factors associated with prevalence of Listeria, Salmonella and Escherichia coli 0157:H7 in the rural household environment, and to provide scientific data for the development of reheating instructions for frankfurters in the home setting. To study risk factors associated with Listeria, Salmonella and Escherichia coli 0157:H7 prevalence in rural Colorado households with or without ruminants, households were recruited, and samples from food and the environment, as well as behavioral data from the primary foods preparer in the house, were collected. Listeria was isolated from refrigerators, kitchen sinks, shoes soles, clothes washing machine and food samples, with higher prevalence in households with ruminants. No sample was found positive for E. coli 0157:H7, and Salmonella was isolated from one refrigerator, one washing machine, one working glove, and two shoe samples. Results indicated that behavior related to handling and cooking of perishable foods affected the probability of household samples testing positive tor Listeria, regardless of presence of ruminants. Personal cleanliness habits were related to presence of Listeria on shoe soles, clothes washing machine, and working gloves. Shoes testing positive in households with ruminants were more frequently associated with multiple positive environmental samples compared to households without ruminants. Results indicated that consumer education on handling and storing perishable foods, and animal handling to prevent contamination of the household through shoes or clothes may reduce prevalence of Listeria in home environments. Two studies evaluated reheating of frankfurters inoculated with L. monocytogenes with or without antimicrobials. In both cases, frankfurters were formulated with or without 1.5% potassium lactate and 0.1% sodium diacetate and were inoculated with a ten-strain composite of L. monocytogenes. After inoculation, frankfurters were vacuum packaged and stored under conditions simulating manufacturing/retail and consumer storage. In one study, after the appropriate storage time, frankfurters were placed in a bowl with water and treated in a household microwave oven. Exposure to high power for 75 s reduced pathogen levels (0.7±0.0 to 1.0±0.1 log CFU/cm2) to below the detection limit (<-0.4 log CFU/cm2) on frankfurters with actate/diacetate. On frankfurters without lactate/diacetate, initial levels of L. monocytogenes (1.5±0.1 to 7.2±0.5 log CFU/cm2) on untreated samples increased as storage in vacuum and aerobic packages progressed. For this formulation, the exposure to high power for 75 s produced reductions between >1.5 and 5.9 log CFU/cm2. Depending on the treatment and storage time, the water used to reheat the frankfurters had viable L. monocytogenes counts of <-2.4 to 5.5±0.5 log CFU/ml. Results indicated that levels of L. monocytogenes contamination <3.7 log CFU/cm2, on frankfurters can be significantly (P>0.05) reduced by microwave oven heating at high power for at least 75 s. Higher contamination levels, such as those found on frankfurters without lactate/diacetate and stored for a prolonged period of time, require longer exposure to microwave heating in order to render the product safe for consumption. In the other study, inoculated frankfurters were treated with hot water after different storage periods to evaluate the destructiveness of different time and water-temperature combinations L. monocytogenes. Treatments at 80°C (60, 120 s) and 94°C (30, 60 s) reduced pathogen counts on frankfurters with PL/SD to at/below the detection limit (<-0.4 log CFU/cm) from initial levels on control (immersed in 25°C water for 300 s) samples. For frankfurters without PL/SD, where pathogen numbers reached 6.1 log CFU/cm2 on 60-day old vacuum-packaged product stored aerobically for 7 days, hot water treatments reduced counts by 1.0 (30 s/80°C) to >6.0 (120 s/94°C and 300 s/94°C) log CFU/cmz. No survivors were detected in the heated water after any treatment (detection limit <-2.5 log CFU/ml). While low levels of L. monocytogenes on frankfurters can be inactivated with short exposure to hot water, increased contamination that may occur as the product ages needs longer times and/or higher temperature for inactivation.
Open Access
Effects of pre-slaughter cattle management on postmortem tenderization of beef
(Colorado State University. Libraries, 2009) Gruber, L. Sandra, author; Tatum, J. Daryl, advisor
Two independent studies were used to investigate the effects of pre-slaughter cattle management on postmortem tenderization of beef. In experiment I, relationships between behavioral and physiological symptoms of pre-slaughter stress and beef LM tenderness were examined using calf-fed steers (n = 79) and heifers (n = 77). Pen, chute, and post-transportation behavior scores were assigned to each animal. Physiological indicators of stress included cortisol, epinephrine, creatine kinase, lactate, glucose, heart rate, respiration rate, and rectal temperature. Positive correlations (P < 0.05) between behavior scores and physiological parameters indicated that cattle that exhibited behavioral symptoms of stress also responded physiologically. Mean Warner-Bratzler shear force (WBSF) was positively correlated (P < 0.05) with all 3 measures of stressful behavior (r ≥ 0.23). Plasma lactate concentration at slaughter was associated (P < 0.05) with mean WBSF and response to postmortem aging. In Experiment II, effects of genotype and implant program on LM and gluteus muscle (GM) postmortem tenderization were investigated using crossbred steer (n = 185) and heifer (n = 158) calves. The 3-marker GeneSTAR Tenderness panel was used to determine each animal's genotype. Calves were assigned to 1 of 2 implant programs, conventional or delayed. Steaks from conventionally implanted cattle had WBSF values that were approximately 0.2 kg higher (P < 0.05) than steaks from animals that received a single delayed implant, but only during the early postmortem period (3 to 7 d). For both muscles, a linear effect of genotype on WBSF was detected (P < 0.05). Steaks from cattle with most desirable genotype had WBSF values 0.33 kg lower than steaks from cattle with the least desirable genotype. Pre-slaughter factors (sex, implant program, and genotype) controlled in Experiment II each accounted for less than 10% of the explained variation in tenderness of the experimental population. Results of Experiment I identified behavioral and physiological symptoms of acute pre-slaughter stress that were associated with pH-independent differences in tenderness. Findings from Experiment II suggest that pre-slaughter cattle management can impact beef tenderness, but the factors evaluated only accounted for a small proportion of variation in beef tenderness for the experimental population.