Browsing by Author "Holt, Timothy N., committee member"
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Item Open Access An in vitro system evaluation of the rumen microbiome and rumen fermentation characteristics as a result of differing feed additives(Colorado State University. Libraries, 2019) Reyes, Arquimides A., author; Delmore, Robert J., advisor; Belk, Keith E., committee member; Engle, Terry E., committee member; Woerner, Dale R., committee member; Holt, Timothy N., committee memberTo view the abstract, please see the full text of the document.Item Open Access Angus cattle at high altitude: pulmonary arterial pressure, estimated breeding value and genome-wide association study(Colorado State University. Libraries, 2016) Zeng, Xi, author; Thomas, Milton G., advisor; Enns, R. Mark, advisor; Speidel, Scott E., committee member; Holt, Timothy N., committee memberTo view the abstract, please see the full text of the document.Item Open Access Benchmark of lamb quality in U.S. retail and foodservice markets(Colorado State University. Libraries, 2015) Hoffman, Travis William, author; Belk, Keith E., advisor; Woerner, Dale R., committee member; Ahola, Jason K., committee member; Pendell, Dustin L., committee member; Holt, Timothy N., committee memberQuality is an accumulation of attributes that satisfy customer preferences and expectations. Lamb quality is a moving target that means different things to the supply chain and sheep/lamb industry stakeholders. The objectives of this research were to determine the rank, definition, relative preference, and willingness to pay (WTP) for seven quality attributes and quantify product attributes of lamb at U.S. retail markets. Structured interviews of retail and foodservice respondents were conducted from May 2014 to March 2015 via face-to-face or telephone with lamb/protein purchaser representatives of retail (n = 60), foodservice (n = 45), and purveyor (n = 15) marketing sectors. Shares of preference (relative percentage of preference) in best/worst evaluation for all interviews indicated that eating satisfaction (38.9%) was the most important attribute. Shares of preference for all seven specified quality attributes were statistically different from each other (P < 0.05). Credence attributes of origin (17.2%) and sheep raising practices (13.6%) ranked second and third overall, respectively. Physical product characteristic traits of product appearance/composition (10.5%) and weight/size (8.5%) were ranked fourth and fifth in shares of preference, respectively. Nutrition/wholesomeness (7.1%) ranked sixth and product convenience/form (4.2%) ranked seventh in the overall ranking across all sectors of retailer, foodservice, and purveyor interview respondents. In WTP analyses, origin (25.8%) and sheep raising practices (20.0%) had the greatest likelihood of being a non-negotiable requirement for lamb purchasers. Eating satisfaction was the trait most likely to receive a premium (71.7%) from buyers, and product assurance of eating satisfaction generated the greatest average WTP premium (18.6%). This research indicated, across all sectors, eating satisfaction, defined as lamb flavor/taste, was the most important quality trait to those who purchase lamb. In-store evaluations of retail lamb labels showed that lamb shoulder and loin chops originating from the U.S. garnered the greatest price premiums compared to either New Zealand or Australian lamb (P < 0.05). Lamb was merchandised to American consumers at specialty type stores at an increased price per kg premium than either locally owned or national grocery chains (P < 0.05). Lamb shoulder prices at retail were merchandised with the greatest premium for product of U.S. origin from a specialty store packaged in modified atmosphere packaging and labeled with local (+ $5.42/kg) and natural (+ $5.40/kg) claims (P < 0.05). Lamb loin prices at retail were merchandised with the greatest premium for product of U.S. origin from a specialty store merchandised in a full service case or modified atmosphere packaged and labeled with a source verified and branded (+ $7.21/kg) label claim (P < 0.05). Shoulder and loin chop prices analyzed via hedonic modeling were not different for store location (East, Central, and West) nor USDA process verified Never-Ever 3 claim (P > 0.05). Additionally, this research indicated that lamb loin and rib chops purchased at U.S. retail markets originating from U.S. lamb were the most muscular. Loin eye area of loin chops from U.S. origin were greater (19.55 cm2) than Australian chops (16.77 cm2), and chops from New Zealand (14.52 cm2) were the least muscular (P < 0.05). Also, Australian lamb (0.64 cm) had a trimness advantage of external fat of loin chops compared to lamb originating from either the U.S (0.84 cm) or New Zealand (0.86 cm; P < 0.05). Lamb producers should strive to place a strategic emphasis on quality attributes identified in this research to ensure eating satisfaction and lamb flavor are optimized for American Lamb, and to produce lamb with product authenticity attributes requested by retail and foodservice sectors, and inevitably American lamb consumers. An important application of the research included the development of an American lamb quality mission to: improve the consistency of quality, cutability, and marketability of American lamb with a consumer driven focus. The final phase of this project was a sheep/lamb industry strategy workshop that identified goals to: 1) Address factors contributing to lamb flavor, their impact on consumer satisfaction, and align flavor characteristics with target markets; 2) Improve lamb management to hit market-ready targets for product size, composition, and eating satisfaction while reducing production costs; and 3) Identify and capitalize on market opportunities for American lamb. A continuous improvement mentality is essential to lamb quality management throughout the supply chain in order to maintain (and increase) market share and demand for American lamb.Item Open Access Characterization of pulmonary hypertension status and utilization of multi-omics analyses to discover variants that may inform selection against high mean pulmonary arterial pressure in Angus cattle(Colorado State University. Libraries, 2020) Jennings, Kaysie Jean, author; Thomas, Milton G., advisor; Coleman, Stephen J., advisor; Enns, R. Mark, committee member; Speidel, Scott E., committee member; Holt, Timothy N., committee memberThis multi-part research characterizes pulmonary hypertension (PH) from a physiologic and genetic point of view using the indicator trait mean pulmonary arterial pressure (PAP). Three aims were designed to address the research objective of investigating the genetics underlying PAP for the purposes of variant discovery. The first aim sought to identify different PAP phenotypes based on altitude and diet during the stocker and finishing phases of production. This longitudinal study evaluated steers with a moderate PAP (41-48 mmHg) from yearling age until harvest, collecting PAP and blood gas parameters throughout the study and carcass data at the conclusion. Through this experimental approach, the role of different finishing systems was able to be evaluated and cattle with increased sensitivity to hypoxic conditions were identified. Results from this study indicated that regardless of finishing system, animals exhibited signs of respiratory alkalosis with renal compensation because of hypoxic conditions. The PAP data from this population corroborated that all steers were hypoxic. However, the only carcass quality differences observed were those between cattle that were grain finished compared to those that were grass finished, regardless of altitude. Aim two was to perform next-generation whole genome sequencing for 30 Angus bulls and steers to compare those with high PAP (HPAP) to those with low PAP (LPAP) measures. All cattle sequenced originated from elevations ≥1,500m and were selected based on their pedigree information, as well as PAP observations. The sequence data from these 30 animals were then compared such that sequence from HPAP cattle was compared to that of LPAP cattle. There were 5,543 variants unique to HPAP cattle and 1,690 variants unique to LPAP cattle. Loci across all 30 chromosomes exhibited variation for PAP phenotype. Evaluation of these variants and validation will be necessary to sift through variants that are in linkage or may be less informative. A multi-omics approach was used to perform variant discovery based on the PAP phenotype in aim three. Through combination of RNA sequence with DNA sequence, the list of variants relevant to PAP phenotype was filtered from millions of variants to hundreds of variants. Transcriptome data was compared for each of six tissues between HPAP and LPAP cattle. These variants were then compared to one another to determine which variants were detected in each PAP category across all six tissue types. Those variants were then compared to the DNA sequence from aim two to elucidate concordant variants for HPAP and LPAP cattle respectively. There were three variants that were unique to LPAP cattle and were concordant between DNA and RNA sequence. However, none of these variants were within 1,000bp of a gene recognized in the ARS-UCD1.2 bovine genome assembly and were therefore considered less informative. There were 523 variants unique to HPAP cattle. Within that population there was a subset that was either near or within a gene. There were six genes that were considered informative for further investigation. Three of those genes were uncharacterized genes on chromosome 16. The other three (U6, SIMC1, CDH23), while not well documented in cattle, had functions in humans that would indicate their function could affect PAP phenotype expression. These genes and the variants within them could be useful for selection if validated in a larger population.Item Open Access Feedlot heart disease: understanding heart score and its relationships to economically relevant traits(Colorado State University. Libraries, 2022) Kukor, Isabella, author; Speidel, Scott E., advisor; Enns, R. Mark, advisor; Holt, Timothy N., committee member; Thomas, Milton G., committee memberThe increasing occurrence of feedlot heart disease caused by pulmonary hypertension has precipitated a growing concern from producers and geneticists alike. Utilization of genetic technology for selection and breeding decisions has made a substantial amount of progress in past decades within economically relevant traits, but the focus on high performing cattle may have had adverse consequences on cardiovascular fitness. Pulmonary hypertension has become a more frequent occurrence in low to moderate elevation feedlots, causing feedlot death and the potential to predispose cattle to co-morbidities. Previously, once considered only a high-altitude issue, pulmonary hypertension appears prevalent in high genetic merit cattle within moderate elevation, high plains feedlots. With no options for treatment, management, and prevention in feedlot cattle may be the only strategy for producers struggling with the balance of desirable, fattening cattle and pulmonary hypertension risk. The objective of this study was to establish the foundation for a new heart grading system known as heart score and discover its genetic and phenotypic relationships with economically relevant traits and differentiate phenotypic differences between healthy and unhealthy scored Angus-influenced cattle. The third chapter of this thesis included phenotypic differences between cattle with healthy and unhealthy heart scores (n = 1,422). Data were obtained from Cactus Feed Yard LLC in Canyon, Texas over a two-year period (2020-2022). Means were compared between heart score groups (1,2 & 3+) to test for significant differences between the two groups. Linear models and the ANOVA table displayed significant fixed effects to each model. Systolic, diastolic, PAP, and marbling scores differed among groups (P < 0.05), while hot carcass weight displayed a tendency (P < 0.10). Unhealthy heart scored cattle tended to be heavier carcasses associating heavier cattle with pulmonary hypertension. Healthy heart scored animals had overall lower (P < 0.05 ) PAP, systolic, and diastolic measurements. The fourth chapter of this thesis highlighted the differences between repeated PAP measurements at 9 and 14 months of age. The cohort of Angus influenced cattle were housed at a feedlot in Canyon, TX and was a moderate altitude (1,080 m). Repeated PAP measurements exhibited an increase in PAP measurements between 9 months and 14 months of age, which were later grouped by their heart scores. No differences were observed among heart scored cattle at 9 months (mean minimum: 39.61 ± 2.47; mean maximum: 40.36 ± 3.47) but distinct differences were observed among cattle grouped in their 14-month PAP (mean minimum: 45.27 ± 5.69; mean maximum: 79.20 ± 21.09). High heart scores were associated with higher PAP measurements. There was a correlation of 0.20 between the measurements showcasing a positive trend between measurements, but also the inability of PAP measurements taken at 9 months may not be predictive of cattle's scores at 14-month-old. Furthermore, there were no differences between phenotypic traits of the cattle who had greater PAP differences between their measurements. The third study estimated the heritability of heart score and the phenotypic relationships with economically relevant traits (n = 1,507) in progeny of 88 sires. Phenotypes included heart scores, PAP (14 months), hot carcass weight, marbling, ribeye area, and backfat. Heart score was found to have a moderate heritability estimate 0.28 ± 0.10. Heart score had a very strong genetic correlation with PAP, and strong correlation with hot carcass weight. Positive genetic correlations were found between heart scores and carcass traits with genetic correlations between 0.07 to 0.63. Overall, these results suggest heart scores to be useful in genetic selection for a healthier cardiopulmonary system. while not drastically influencing carcass traits.Item Open Access Pulmonary arterial pressure in Angus cattle: environmental influences and relationship with growth and carcass traits(Colorado State University. Libraries, 2017) Pauling, Rachel, author; Enns, R. Mark, advisor; Holt, Timothy N., committee member; Speidel, Scott E., committee member; Thomas, Milton G., committee memberRight-side heart failure (RHF) resulting from hypoxia induced pulmonary hypertension is most commonly observed in cattle located at high elevations, but has been observed in some feedlot cattle residing at low elevations as well. Beef cattle producers typically use pulmonary arterial pressure (PAP) observations to predict an animal's susceptibility to RHF. The objective of this this study was to investigate the effect of elevation on PAP measures, and to evaluate the relationship between PAP, growth traits, and carcass traits in Angus cattle. The first study utilized PAP and elevation data obtained from the American Angus Association (AAA, n = 4,511), Colorado State University Beef Improvement Center (n = 5,433), and Dr. Timothy Holt DVM (n = 4,821). A univariate analysis of PAP as used to obtain elevation solutions to be input to a polynomial regression to determine high versus low elevation (1,620 m). Then a bi-variate analysis was performed to evaluate the genetic relationship between PAP observations obtained at high elevations as well as low elevations. Results from this study indicate that PAP observations obtained at any elevation can be considered the same trait with a genetic correlation of (0.83 ± 0.15). The second study utilized data obtained from AAA (n = 4,509) which included PAP, growth, and carcass traits. Multivariate analyses of PAP and growth traits, as well as PAP and carcass ultrasound traits were used to obtain estimates of heritability and genetic correlations. Results from these analyses indicated that there are moderate genetic correlations between PAP and maternal birth weight (0.55 ± 0.12) as well as PAP and ultrasound ribeye area (0.24 ± 0.12). These results suggested that selection for increased growth and muscling in cattle could consequently increase PAP observations.Item Open Access The effects of molybdenum water concentration on feedlot performance, tissue mineral concentration, and carcass quality of feedlot steers(Colorado State University. Libraries, 2017) Kistner, Madison, author; Engle, Terry, advisor; Wagner, John J., advisor; Holt, Timothy N., committee memberThirty cross-bred steers (initial BW 375 ±37.2, replicate 1; and 535.0 ± 39.4 kg, replicate 2) were utilized to investigate the effects of Mo water concentration on performance, carcass characteristics, and mineral status of feedlot steers fed a growing and finishing diet for 151 and 112 d for replicate 1 and replicate 2, respectively. The experimental design was a randomized complete block design. Steers were blocked by weight and then divided into 2 weight block replicates each consisting of 15 steers. Steers were randomly assigned within block to one of 5 treatments (3 pens/treatment; 1 steer/ pen; 2 replicates/treatment). Water treatments consisted of: 1) 0.0 µg, 2) 160 µg, 3) 320 µg 4) 480 µg Mo/L, and 5) 960 µg of supplemental Mo/L added as Na2MoO4 to the drinking water. Steers were housed in individual pens that contained individual 265 L water tanks for monitoring water intake. Daily water intake was recorded for each steer. Steers were individually weighed on 2 consecutive days at the beginning and end of the experiment and interim weights and jugular blood samples were obtained every 28 d. Liver biopsies were obtained on d0 and 84 from each steers. Steers were transported to a commercial abattoir, slaughtered, and individual carcass data and liver samples were collected. Initial BW was used as a covariate for statistical analysis of the data and significance was determined at P ≤ 0.05. No differences were observed for final BW (P ≤ 0.98). Overall ADG, DMI, feed efficiency and water intake were similar across treatments. Hot carcass weight, dressing percentage, yield grade, LMA, adjusted fat thickness, KPH, and marbling scores were similar across treatments. Liver and plasma Cu, Mo, and Zn concentrations were similar across treatments. These data indicate that water Mo concentration had no impact on performance, mineral status, water intake, and carcass characteristics in feedlot steers fed a high concentrate diet.Item Open Access The effects of olive meal supplementation on feedlot performance and longissimus muscle fatty acid composition of Wagyu steers and the impact of calcium dose and olive meal on in vitro rumen fermentation characteristics(Colorado State University. Libraries, 2022) Tangredi, Briana V., author; Engle, Terry E., advisor; Delmore, Robert J., committee member; Holt, Timothy N., committee memberTwo experiments were conducted to evaluate the effects of olive meal supplementation on feedlot performance of Wagyu steers and the impact of Ca dose and olive meal on in vitro rumen fermentation characteristics. Experiment 1: Eighty-three American Wagyu steers (725 ±10.7 kg) were used to evaluate the effects of olive meal supplementation on feedlot performance and carcass characteristics. The steers were blocked by BW. The heaviest 8 steers were stratified into two pens containing 3 or 4 steers per pen with similar pen BW. This was considered a paired weight block. This process was repeated until all steers were assigned to pens. Each pen contained 3 or 4 steers/pen with 11 replicates/treatment. Steers were blocked by initial body weight (BW) and randomly assigned within block to one of two treatments. Treatments consisted of: 1) Control (basal ration with no olive meal) + 1 kg of supplemental cracked corn per animal per day, or 2) Control diet + 1 kg of supplemental olive meal per animal per d ay. Steers were housed in feedlot pens (n=4 steers/pen; 11 replicates/treatment) and fed a traditional American Wagyu finishing diet (DM basis: 68.4% DM, 14.3% CP; 74.8% TDN, 1.16 Mcal/kg NEg, 5.3% crude fat). Diets were delivered to pens, once daily, in the morning in amounts to allow ad libitum access to feed over a 24 h period. Olive meal and cracked corn were top-dressed to the appropriate treatment pens immediately after delivery of the basal ration. Steers were individually weighed on d -1 and 0, and approximately every 28 d throughout the 177 d experiment. Equal numbers of steers per treatment were slaughtered throughout the experiment and carcass data were collected. Steers receiving olive meal had a lower final BW, ADG, DMI, and FE (P < 0.05) when compared to steers receiving the control diet. Longissimus muscle C18:1 tended to be greater (P < 0.06) in steers receiving olive meal when compared to controls. Under the conditions of this experiment, feeding olive meal at 1.0 kg/ animal /day reduced live animal performance and had minimal impacts on longissimus muscle fatty acid composition. Experiment 2: Rumen fluid from three beef steers (480 ± 10 kg) fitted with rumen canulae, was used to investigate the impact of Ca dose and olive meal on in vitro rumen fermentation characteristics. Steers were fed a high concentrate finishing diet for 21 d and rumen fluid was collected from each steer 2h post-feeding. A 2 x 4 factorial arrangement of treatments was used for this experiment. Factors included: 1) 0 or 5% olive meal and 2) Ca dose: 0, 0.02, 0.04, and 0.08% Ca from CaCl2. A McDougall's buffer-rumen fluid mixture (1:1; 30 mL 5 total volume) was added to conical tubes containing 0.5g of the ground basal diet with the appropriate treatments and incubated at 39°C for 0, 4, 8, and 12h (5 replicates per treatment per time point). After incubation, supernatant was removed for VFA analysis and the remaining digesta was dried to determine DM disappearance (DMD). There were no olive meal x Ca interactions for any response variables measured. At 4 and 8 h post incubation digestion tubes containing 0.04% Ca had greater (P < 0.001) DMD when compared to all other Ca doses. At 12 h post incubation, DMD was greater (P < 0.001) in digestion tubes containing 0.02% and 0.08% Ca compared to all iv other Ca doses. At 8 h post incubation, molar proportions of acetic acid were greater (P < 0.03) in digestion tubes containing olive meal compared to no olive meal and were greater (P < 0.001) in digestion tubes containing 0.08% Ca compared to all other Ca doses. At 12 h post incubation, iso-butyric acid (P < 0.01) and butyric acid (P < 0.02) were greater in digestion tubes containing 0.02% and 0.04% Ca compared to all other Ca doses. Butyric acid was lesser (P < 0.02) with olive meal inclusion at 12 h. Total VFA concentrations were similar across treatments. These data suggest that Ca and olive meal may impact in vitro fermentation. Dietary treatment was a significant (P < 0.05) source of variation for caproic (C6:0), capric (C10:0), linoleic (C18:2n-6), linolelaidic (C18:2n-6 trans), and docosahexaenoic (C22:6n-3) longissimus muscle fatty acids. Steers receiving the control diet had greater C6:0 (P < 0.02), C10:0 (P < 0.02), C18:2n-6 trans (0.02), and C22:6n-3 (P < 0.05) fatty acids when compared to cattle receiving olive meal. Steers receiving olive meal had greater C18:2n-6 (P < 0.04) when compared to controls. All other fatty acids identified were similar across treatment. Based on these data Ca addition at the concentration supplied in this experiment did not inhibit biohydrogenation of unsaturated fatty acids but did improve fermentation characteristics.