Department of Animal Sciences

Permanent URI for this community

https://hdl.handle.net/10217/100318

These digital collections include faculty publications and theses and dissertations from the Department of Animal Sciences, and proceedings of the "Beef Cow Efficiency Forum" (1984). Due to departmental name changes, materials from the following historical departments are also included here: Animal Husbandry; Animal Nutrition.

See also the archival collection of Dr. Temple Grandin, a Colorado State University professor of animal sciences and world-renowned autism spokesperson.

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Open Access
2022 National Lamb Quality Audit: Phase I: Supply chain perceptions of the U.S. lamb industry. Phase II: In-plant survey of carcass characteristics related to quality and value of fed lambs and mutton
(Colorado State University. Libraries, 2023) Newman, Lauren, author; Stackhouse-Lawson, Kim, advisor; Place, Sara, committee member; Nair, Mahesh Narayanan, committee member; Garry, Franklyn, committee member; Finck, Jessica, committee member
The U.S. sheep and lamb population has slowly declined over the last eight decades, from 56 million head in 1942 to five million head in January of 2023. Sheep, often referred to as mutton in the meat industry, are mature animals that have at least two permanent incisors, spool joints, and are typically over 24 months of age. Lambs are considered young animals that lack permanent incisors, have at least one break joint, and are usually less than 14 months (USDA,1992). The U.S. lamb industry faces competition from imported lamb from Australia and New Zealand that is less expensive. This imported product increases the lamb supply within U.S. wholesale and retail stores, which, along with increased production costs, has raised concerns about the future viability of the U.S. lamb industry. In response to this pressure, the lamb supply chain can prioritize attributes that both reduce production costs and promote consumer demand. The first step in this process is to measure data from production through lamb carcass quality characteristics, especially data captured in the manufacturing settings. Benchmarking is necessary to identify needs to drive quality enhancements and to ultimately drive improvement and profitability of the lamb industry. The current National Lamb Quality Audit (NLQA) seeks to fill this gap by capturing baseline data from broad scope of the supply chain through perception surveys and in-plant audits. This baseline information will inform the lamb value chain on the current perceptions and lamb quality characteristics that may aid in identifying attributes to reduce costs and increase consumer demand. The NLQA, conducted three times since 1992, assesses the industry's progress on various quality characteristics that ultimately affect consumer demand for lamb. The most recent audit, conducted in 2015, primarily focused on the foodservice segment of the industry. As sheep genetics, management practices, available resources, and consumers' needs and expectations constantly evolve, more frequent audits that capture the entire supply-chain should be considered. The 2022 NLQA audit is designed to repeat successful portions of the 2015 audit, including a new supply chain survey to assess perceptions about the U.S. lamb industry and in-plant carcass characteristics. In phase I, 155 surveys were conducted from May 2022 through September 2022 to understand and quantify perceptions of the U.S. lamb industry. The survey was administered using a software package (Qualtrics®, Provo, Utah) customized to develop a structured order of questions for each industry segment. The survey was distributed via in-plant visits, social media, and email. Survey respondents remained anonymous, each taking approximately ten minutes to complete. Statistical analysis was conducted in Microsoft Excel and the Qualtrics® software. Thirty-two states were represented, with 88 percent of respondents identifying as the owner/operator of their respective business or operation and 86 percent representing commercial breeding operations. Respondents were asked to rank topics based on importance to their operation from 1 (least important) to 10 (most important). Animal welfare (8.9), lamb quality (8.4), and sustainability (7.6) were of most importance to producers. Respondents were also prompted to rank significant challenges in the industry (1=most important and 10=least important). The most significant challenges identified were operation costs (3.04), market volatility (3.70), and labor (4.08). Open-ended responses for defining sustainability were sorted and narrowed in terms of descriptions to find commonalities between respondents. Central themes from respondents included environmental stewardship, profitability, and producing high-quality lamb products. Results from the survey will provide valuable insight to discern gaps and opportunities between producers' viewpoints and data collected in plants to develop educational material to improve lamb quality. For phase II, in-plant assessments were conducted in four of the largest U.S. commercial lamb processing facilities across six production days from June to September 2022. On each production day, 50 percent of carcasses harvested and chilled were surveyed. Both hide-on and hide-off carcasses (n=2,605) and chilled carcasses (n=2,464) were surveyed. On the harvest floor, trained auditors collected data on mud scores, breed type, presence of horns, sex, wool length, and physiological age indicator data. Additionally, hot carcass weight (HCW), measured fat thickness (MFT), and reported USDA yield and quality grades were collected in the cooler. The distribution and summary functions of JMP® Software were used to determine the frequency distributions, means, standard deviations, and minimum and maximum values. Data was analyzed using the Type III ANOVA procedure, and a pairwise comparison was analyzed for dependent variables by treatment using the least squared means procedure in the 'lsmeans' package, of R© with the Tukey HSD adjustment. Dependent variables were YG, calculated YG, HCW, and MFT. Significance was determined at P-value ≤ 0.05. Phase II used in-plant assessments to benchmark current carcass quality characteristics related value of the fed lamb and mutton industry in the U.S. Among the carcasses (n = 1,605) that were audited for sex, 63.2 percent were wethers, 31.5 percent ewes, and 5.3 percent rams. Two percent of the carcasses were presented with horns. Of the 2,604 carcasses evaluated, 40.2 percent were speckle-faced (white-face and black-face cross), 38.8 percent were white-faced, 18.3 percent were black-faced, 1.46 percent had natural characteristics, and 1.72 percent were hair sheep. The average mud score was 2.12, and the average wool length was 5.03 cm. Additionally, 87.1 percent of the 2,437 carcasses presented two break joints indicating lamb, 5.70 percent with one break joint indicating yearling mutton, and 7.18 percent with no break joints indicating mutton. The average HCW (n=2,464) was 39.9 kg, whereas the MFT was 0.97 cm. The USDA stamped yield grade was 2.71 and 68.5 percent graded choice (CH), 22.6 percent graded prime (PR), and 8.9 percent were not graded. The 2022 NLQA in-plant survey of carcass quality characteristics will provide a current benchmark for carcass characteristics of lamb processed in the U.S. The data from this study can help industry segments to understand and develop strategic initiatives to improve the quality of fed lamb and mutton.
Embargo
A comprehensive study of Salmonella infections and microbial analysis of probiotics on beef cattle
(Colorado State University. Libraries, 2023) Thompson, Tyler Warren, author; Nair, Mahesh Narayanan, advisor; Geornaras, Ifigenia, committee member; Belk, Keith, committee member; Noyes, Noelle, committee member; Morley, Paul, committee member
Non-typhoidal Salmonella remains a significant concern for food safety in the United States, causing millions of infections, hospitalizations, and deaths yearly. The Healthy People 2030 initiative set forth by the U.S. Department of Health and Human Services aims to address this issue by establishing goals and objectives for national health promotion and disease prevention, including two objectives focused on Salmonella control in the food supply. The recent declaration of Salmonella as an adulterant in certain poultry products by the U.S. Department of Agriculture further highlights the urgency of this issue. To align with the Healthy People 2030 goals and achieve a 25% reduction in salmonellosis, the U.S. Department of Agriculture's Food Safety and Inspection Service (FSIS) implemented new performance standards for beef products. However, such policies must be supported by quantitative microbial risk assessments (QMRA) to determine their impact on Salmonella infections. Therefore, these analyses would benefit from a systematic review examining existing literature on Salmonella, considering factors such as illness rates, exposure, and bacterial loads. This review included 42 articles that provided data necessary for fitting a dose-response model to empirical data that describes how dose, virulence group, and food vector affect illness (attack) rates. Results from the mixed-effects logistic regression model showed significant impacts of log dose consumed, virulence group, and food vector on illness rates. Notably, Salmonella serogroups of "Higher" virulence were found to be associated with greater odds of illness than "Lower" virulence strains. The study highlights the need for improved data reporting and standardized outbreak investigations to enhance the fitting of models to outbreak data. By considering factors like serovar group and food vector in the modeling process, regulators can demonstrate what influences attack rate to frame more effective food safety policies. In conclusion, this systematic review provides valuable insights into Salmonella infection risk from food sources and emphasizes the importance of evidence-based policies to reduce the burden of Salmonella-related illnesses and improve food safety in the United States. Liver abscesses in beef cattle are a common problem associated with highly-fermentable carbohydrate diets during finishing, leading to decreased production efficiency and aggregate carcass value. Dietary antimicrobial supplementation, such as tylosin, helps to control liver abscesses but raises concerns about selection for antimicrobial resistance. This study examined the impact of a probiotic mixture of propionic and lactic acid bacteria on microbial communities and antimicrobial resistance genes (ARGs) in fecal and liver abscess samples from beef cattle alongside Salmonella populations of mesenteric lymphatic tissues. Treatment diets fed in this study included a probiotic mixture alone (DFM), inclusion of Tylosin (TYL), a combination of including both (DFM+TYL), and a control group diet that did not include any supplements (CON). Fecal samples were collected at the time that feeding started, and then 28 d before arriving at the abattoir, where liver abscesses and mesenteric lymph nodes were sampled. Fecal and liver abscess samples were subjected to 16S rRNA and targeted enriched shotgun metagenomics to evaluate microbial communities and resistance genes of bacteria present. A portion of the liver abscess and mesenteric lymph nodes were tested for presence of Salmonella using PCR with further analysis of enumeration and serotype classification for mesenteric lymph nodes. Results showed no differences (P > 0.05) between the fecal microbiomes of the different treatment groups, and the addition of tylosin or probiotic mixture did not impact the fecal resistome. Similarly, no differences (P > 0.05) were observed between the liver abscess microbiomes of the different (P > 0.05) treatment groups, with Fusobacteria and Bacteroidetes being the dominant phyla in liver abscesses. Results indicated that incorporating DFMs did not affect Salmonella prevalence in the cattle's mesenteric lymph nodes or liver abscesses. Presence of Salmonella was found at low levels in only 22% of samples (91 positive out of 503 samples), just below 1 log CFU/g, and was predominantly represented by the C1 serogroup in mesenteric lymph nodes. These findings suggest that while diet interventions may not have a substantial impact, Salmonella can colonize mesenteric lymphatic tissues in cattle at low frequencies and concentrations. Treatment groups tested had no impact (P > 0.05) on fecal and liver abscesses microbiomes and resistance gene presence, along with no impact on Salmonella prevalence in liver abscesses or mesenteric lymphatic tissues.
Open Access
A needs assessment for Colorado beef producers: understanding rancher priorities, preferred communication strategies, and influential factors on prioritization and relationships with land grant universities
(Colorado State University. Libraries, 2018) Dideriksen, Sarah M., author; Rhoades, Ryan D., advisor; Ahola, Jason K., advisor; Fankhauser, Terry R., committee member; Mooney, Daniel F., committee member; Román-Muñiz, Ivette N., committee member
To view the abstract, please see the full text of the document.
Open Access
A pilot study of behavioral and physiological markers of stress in horses during equine-assisted learning for youth with social-emotional concerns
(Colorado State University. Libraries, 2023) Singh, Ashley, author; Grandin, Temple, advisor; Peters, Caiti, advisor; Matlock, Sarah, committee member; Nett, Terry, committee member
Equine Assisted Learning (EAL) is an increasingly popular service in providing comfort and life skills for youth who have social-emotional concerns. There is mixed evidence in previous research that shows increased stress in horses in EASs who are interacting with the population of youth with social- emotional concerns. This pilot study aimed to look physiological and behavioral indicators of stress in horses involved in equine assisted learning for youth with social- emotional concerns. This within-subject design included 11 horses and 18 human participants. Indicators of equine stress included salivary cortisol, eye temperature, and equine behavior. On average, indicators of stress in horses were not significantly different while the horses interacted with youth with social- emotional concerns compared to a control condition. There was a significant condition x week interaction effect such that horses demonstrated higher levels of cortisol in week 3 while interacting with youth with social- emotional concerns compared to the control condition, but this difference did not exist by Weeks 5 and 7. These condition by week interaction effects did not exist in equine eye temperature or behavior. This study provides evidence that interacting with youth with social- emotional concerns was not more stressful for horses that interacting with another population that commonly participates in EAL.
Open Access
A proof of concept to differentiate among differences in flavor of American lamb using volatile flavor compound analysis
(Colorado State University. Libraries, 2023) Isaacs, Karissa Ann, author; Woerner, Dale R., advisor; Belk, Keith E., advisor; Tatum, J. Daryl, committee member; LeValley, Stephen B., committee member; Heuberger, Adam L, committee member; Meiman, Paul, committee member
Experiments were conducted on lamb legs (n=25 per treatment) from 3 dentition groups [ young lambs (0 permanent incisors), yearlings (2 permanent incisors) and mature sheep or mutton (>2 permanent incisors)] to establish a proof of concept for differentiating the inherent differences in flavor that exist in meat from ovine animals of various age classes using volatile flavor compound analysis. The legs were selected from commercial processing facilities. Differences among age group, breed type, sex and production background were evaluated for sensory analysis and volatile compound analysis. Trained panelists evaluated ground meat patties from each leg for lamb flavor intensity and off flavor intensity. In addition, samples were analyzed to determine percentages of lipid, moisture, protein, and ash as well as to identify volatiles produced during cooking of a raw composite of lean and fat from the external surface of the leg. Analysis of variance was conducted for sensory flavor attributes relative to animal age and production background (grain vs grass) helped to describe the experimental samples. Ratings for lamb flavor intensity were higher (P < 0.05) for lamb carcass samples than for yearling carcass samples, and lamb flavor intensity scores were similar for lamb and mature age classes. Off-flavor intensity ratings were highest (P < 0.05) for samples from mature lamb carcasses, while lamb and yearling samples produced the lowest (P < 0.05) off-flavor intensity ratings. Lamb flavor intensity and off-flavor intensity ratings were higher (P < 0.05) for grass-fed lamb samples compared to grain-fed lamb samples. Mature samples had the greatest (P < 0.05) off-flavor intensity, while lamb and yearling samples had the least (P < 0.05) off-flavor intensity. Grass-fed lamb samples had the higher (P < 0.05) lamb flavor intensity scores and higher (P < 0.05) off-flavor intensity scores. Correlations between sensory attributes and metabolites helped to narrow the 500+ to 50 of significance. Findings indicated that metabolites (volatile compounds) were related to flavor of sheep meat. Finally, regression techniques helped to predict lamb flavor intensity, off flavor intensity and proof-of-concept for classifying lamb flavor.
Open Access
Ability, repeatability, and reproducibility of rapid evaporative ionization mass spectrometry to predict beef quality attributes
(Colorado State University. Libraries, 2022) Hernandez Sintharakao, Michael J., author; Nair, Mahesh N., advisor; Prenni, Jessica E., advisor; Morgan, James B., committee member; Sharp, Julia L., committee member
Tenderness, juiciness, and flavor are beef quality attributes that influence consumer satisfaction eating beef. Rapid evaporative ionization mass spectrometry (REIMS) is a novel technique that provides chemical information of biological tissues with the potential to predict beef quality attributes. Two studies were conducted to evaluate the ability of REIMS to predict quality attributes of beef (study I) and to evaluate the repeatability and reproducibility of REIMS in a beef matrix (study II). In study I, USDA Select or upper two-thirds Choice (n = 42, N=84) striploins and tenderloins were collected approximately 36h post-mortem from a commercial beef abattoir. Slivers of the longissimus dorsi muscle between the 12-13th rib were collected during grading (GR, 36h post-mortem) and analyzed using REIMS. Striploins (LM) and tenderloins (PM) were cut into portions and assigned to 6 aging periods (3, 14, 28, 42, 56, and 70 days). However, only samples aged 3, 14, and 28 days were used to represent industry practices in study I. After aging, portions were cut into 2.54-cm steaks to analyze juiciness, tenderness, and 10 flavor attributes with a trained sensory panel. In addition, tenderness measures were performed using slice shear force (SSF) and Warner-Bratzler shear force (WBF). Samples were categorized by SSF, WBF, and sensory panel tenderness (PT) into "tough" and "tender"; by juiciness into "dry" and "juicy"; and by flavor into "acceptable" and "unacceptable" classes using a composite score of all flavor descriptors. Combinations of three dimensionality reduction methods (principal component analysis [PCA], feature selection, [FS], and a combination of both [PCA-FS]) with 13 machine learning algorithms were used to create classification models based on REIMS data for tenderness, juiciness, and flavor classes at the three aging periods. The predictive ability of the models was assessed with the overall accuracy resulting from 10-fold cross-validation. Among all machine learning algorithms evaluated, the maximum classification accuracies for days 3, 14, and 28 were 94, 87, and 83% for PT; 86, 85, 92% for SSF; 87, 82, and 95 for WBF; 85, 84, and 86% for juiciness; and 87, 89, and 81% for flavor classes, respectively. FS performed the best as a dimensionality reduction method for all PT, juiciness, flavor, and SSF on day 3 and WBF on days 3 and 14. PCA-FS was the best dimensionality reduction method for SSF on days 14 and 28, and WBF on day 28. Extreme gradient boosting machine learning algorithm was the highest performing algorithm for all juiciness models, flavor model on day 28, PT on days 3 and 14, SSF on days 14 and 28, and WBF on days 3. Partial least squared discriminant analysis (PLSDA) performed better for PT day 28 and flavor day 14, while elastic-net regularized generalized linear model, random forest, and support vector machine were the highest performing algorithms for SSF day 3, and WBF days 14 and 28, respectively. Results demonstrated that the chemical fingerprints obtained with REIMS could potentially be used as in situ and real-time technique to sort carcasses by flavor, juiciness, and tenderness. However, overlaps between classes affected REIMS results, and unbalanced data negatively affected model accuracies. Therefore, exploring the full potential of REIMS will require increasing the sample size and developing a sampling method that allows increased separation between sensory evaluations. Study II was performed with REIMS data from all LM and PM samples from the six aging periods (n=1008), two sets of GR samples (n=168, N=84), and quality control (QC) samples (n=29) made from homogenized ground beef. Except for the second set of GR samples, REIMS analysis of all samples was performed at Colorado State University (CSU) using a meat probe as the sampling device. Analysis of all samples was performed over 5 days, including two batches per day. GR samples were evaluated on the first day, and LM and PM data were randomly analyzed on the remaining days. QC samples were analyzed at the beginning, middle, and end of each batch. The second set of GR samples was analyzed at Texas Tech University (TTU) using different mass spectrometry (MS) instruments, technicians, and an iKnife as the sampling device. The stability of REIMS data between burns, batches, and days was evaluated with QC data. Day effect and robustness of REIMS data were evaluated with data from LM and PM samples, and interlab reproducibility was evaluated with data from GR samples. Multiple classification models of muscle type and aging were built with LM and PM data to evaluate the robustness of REIMS and day-to-day variability. Models to predict sensory attributes of beef were used to assess the robustness of REIMS with respect to interlab variability. Coefficients of variation (CV) between burns of the mass bins representing 90% of the total ion current were between 0.7 to 0.98, while the most relevant mass bins showed CV less than 0.3. Variances between batches and collection days were not significant (P < 0.05). PCA of LM and PM showed that data variability by collection day was stronger than muscle type and aging time variability. However, data could classify samples into muscle types and two distant aging times with accuracies higher than 95.6% and 91.0%, respectively. PCA of GR samples showed that data collected in both labs differed, and the predictive models developed with the CSU data did not appropriately predict the quality classes with the TTU data. REIMS collected with the meat probe provides a chemometric profile of beef samples with good repeatability and interday reproducibility but low interlab reproducibility. Consequently, optimization and standardization of sampling methods will be required to improve the interlab reproducibility of REIMS.
Open Access
An evaluation of cattle handling categories in the beef quality assurance feedyard assessment, compliance of large feedyards with these guidelines, and influence of handling practices on behavior and performance of feedlot cattle
(Colorado State University. Libraries, 2015) Woiwode, Ruth, author; Grandin, Temple, advisor; Archibeque, Shawn, committee member; Engle, Terry, committee member; Kirch, Brett, committee member; Paterson, John, committee member; Rollin, Bernard, committee member
Animal husbandry and management practices were surveyed in commercial feedlots to document compliance of select feedlots with Beef Quality Assurance (BQA) guidelines for cattle handling under the premise that this data warrants inclusion in the National Beef Quality Audit (NBQA). The BQA Feedyard Assessment for cattle handling has not yet been fully validated, and this work partially substantiates the current assessment categories. The inclusion of this handling data is essential in order to continue the track record of identifying target areas where improvement is needed, and to document growth and positive performance. Collecting and reporting of survey data is part of the verification and ongoing monitoring process that characterizes an effective HACCP plan, which was the system for management that was adopted during formation of the BQA program. It has been said that producers manage what they measure, and systematic measurement of categories for cattle handling and husbandry practices in the BQA can yield valuable information to assist producers in making management decisions. The NBQA, which has been conducted in five year increments since 1991 has accomplished just that, through the identification of targets where improvement is needed, with corresponding recommendations for improvement. The growing repository of data, collected over the course of time, reflects adjustments the industry has made in an effort to continuously improve the quality and consistency of beef production, and thus increase consumer confidence. BQA is a voluntary program that allows the use of self-assessment or third party audits to ensure compliance with the guidelines of the program. The BQA Feedyard Assessment (FA) provides guidelines for cattle handling in commercial feedlots, and is a useful tool for measuring cattle handling practices. Using these guidelines, select feedlots in 3 states (Colorado, Kansas, and Nebraska) were assessed for six current BQA categories (electric prod use, falls, stumbles, jump and run, and chute operation). These states rank 5th, 3rd, and 2nd, respectively, among all states for the number of cattle on feed each year. These three states were selected based on their ranking among the top five states for number of cattle on feed, and for the high density areas of large (1000+ head) feedyards in each state, accounting for approximately 50% of all US fed cattle each year. The feedyards included in this study were all large (1000+ head capacity) yards, with a mean capacity of 34,000 head. Across 28 sites surveyed, rate of electric prod use was 3.8% vs. the 10% current BQA critical limit (CL); only 2 sites surveyed exceeded the CL with 15% and 45% respective rates; and 12 did not use an electric prod. The rate of cattle falling when exiting the squeeze chute was 0.6% vs. BQA CL 2%, and no site surveyed exceeded the CL. The rate of cattle stumbling when exiting the squeeze chute was 5.7% vs. BQA CL 10%, with 4 sites exceeding the CL and 4 sites that had no stumbles. The rate of cattle vocalizing was 1.4% vs. BQA CL 5%; for cattle that jumped or ran when exiting the squeeze chute, 52% vs. BQA CL 25%; and mean score for cattle that were improperly captured in the squeeze chute and not readjusted was 1.2%, vs. BQA CL 0%. A second study was conducted at a commercial feedlot in Kansas. The objective of this study was to investigate if a relationship exists between handling, and behavior and ADG of feedlot cattle. Upon arrival, Hereford steers (n = 496; initial BW = 304 ± 35.6 kg) of similar genetic background were sorted into four pens to determine the effects of handling on behavior and ADG. Two handling conditions prior to processing and two conditions of release from the squeeze chute were imposed. Prior to processing, handlers were required to quietly walk all steers from their home pen to the processing area (SLOW); or handlers were permitted to bring steers to the processing area in the normal fashion (FAST). Since this condition was applied to pens, pen was considered the experimental unit for the full model. Individual steers were randomly assigned to one of two conditions of release from the squeeze chute. The first was a delay no longer than 30 seconds following the completion of procedures to allow cattle to stop struggling (DELAY); the second was release immediately following the completion of procedures (NORM). Vocalization, chute temperament, exit speed and exit behavior scores were assigned to all steers during intake processing. Paired t-tests determined that cattle exiting the chute at a walk or trot vs a run tended (P=0.08) to have higher ADG. Cattle vocalizing during restraint had lower (P=0.04) ADG than those that did not vocalize. The FAST group showed a tendency to vocalize more frequently than the SLOW group. Pearson’s correlation analysis showed a significant, positive correlation between exit speed and vocalization (P= 0.0021, r= 0.14256), and a significant, negative correlation between exit speed and ADG (P= 0.0036, r= -0.13542). Using this approach, handling was correlated with behavior and ADG.
Open Access
An evaluation of the effectiveness of FreshCase® technology to extend the shelf life of beef and pork
(Colorado State University. Libraries, 2012) Yang, Xiang, author; Belk, Keith E., advisor; Woerner, Dale R., advisor; Chapman, Phillip L., committee member; Tatum, J. Daryl, committee member
This research evaluated the effect of FreshCase®, a novel packaging technology that has been shown to extend the shelf life of whole muscle beef and ground beef, whole muscle pork and ground pork sausages by stabilizing fresh meat color. FreshCase® utilizes a high-barrier nitrite containing film in conjunction with vacuum packaging technology. Storage life was defined by the number of days required to reach an aerobic psychrotrophic plate count of 107 log CFU/g, and all treatmes were stored and evaluated until storage life expired. The storage life for beef steaks stored in FreshCase® packages at 4°C was 36 days; and the shelf life for ground beef stored in FreshCase® packages at 4°C was 12 days. The shelf life for pork chops stored in FreshCase® packages at 1°C was 46 days; and the shelf life for ground pork sausages stored in FreshCase® packages at 1°C was 19 days. Values for CIE a* (redness) were greater (P < 0.05) for FreshCase®-packaged samples for both beef steaks and ground beef with the increase of storage time. Both pork chops and sausages stored in FreshCase® packages retained more acceptable redder color (P < 0.05) than those stored in Control packages throughout storage. By the point at which spoilage was detected, off-odors of putrid, acid, sour and rancidity for FreshCase®-packaged samples were detected, but were present at very low level. Likewise, by the point of spoilage, no significant differences (P > 0.05) were found between samples in control and FreshCase® packages in all off-odors detection for both pork chops and sausages and the intensities of these off-odors were very low. Also, beef and pork samples resulted in very low (1.19 mg malonaldehyde/kg and 0.55 mg malonaldehyde/kg, respectively) TBA values throughout storage. Therefore, utilization of FreshCase® Technology in whole muscle beef and ground beef, whole muscle pork and ground pork sausages results in a more stable fresh red meat color with a low level of off-odors, and lipid oxidation. FreshCase® did not influence microbial growth in vacuum packaged samples.
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 member
To view the abstract, please see the full text of the document.
Open Access
An integral approach for management challenges in the dairy industry
(Colorado State University. Libraries, 2023) Herrera, Natalia, author; Pinedo, Pablo, advisor; Velez, Juan Santiago, committee member; Holt, Timothy, committee member
A growing body of literature recognizes the importance of including an integrated approach to animal welfare and employee well-being in the dairy industry. The current thesis aims to describe this integral approach by presenting two research projects developed in a commercial dairy under the same management. Hence, an animal welfare pilot study was performed on a dairy farm located in northern Colorado, and an employee well-being study was developed on three dairy farms, two located in northern Colorado and one in northern Texas. Both projects were performed during the year 2022 and the dairies are administrated by the same management. The overall structure of this thesis takes the form of three chapters, including each perspective previously analyzed in the current management challenges explored in the dairy industry. Chapter one presents an extensive literature review of both approaches identified as management challenges in the dairy industry. Then, chapter two analyses the results of an online survey undertaken from September through November 2022 that aimed to explore employee adaptation, perception, and understanding of technology in the dairy farm. In order to accomplish the goal of this pilot study, the online survey completed by two-hundred-sixty-six employees was analyzed and the results are presented in chapter two. Chapter three presents the results of an observational study done on cow-calf behavior from the expulsion of the calf up to the separation in a dairy system located in northern Colorado. One-hundred-sixty-seven calving that occurred from May to June were analyzed and the results are presented in chapter three. Results are briefly described next. First, from the adaptation, perception, and understanding of technology in the dairy farm study, employees recognize and have positive feelings towards the technology implemented at work, where they highlighted the understanding of its benefits, and recognized the technology as a tool that helps them to be more efficient. However, the challenges to adapting to new technology were mainly determined to be personal limitations, such as not knowing the language of the technology and impairments to seeing. Also environmental limitations were recognized by the employees such as cold weather, wind, or an environment that is too dark or too bright. Lastly, the level of perception of technology was found to be associated with the level of education and level of English of the employee, but no significant differences were identified by age or gender. Findings are promising and the current thesis invites the academia to extended this type of research in other livestock operations that adopt precision livestock farming technology. Second, from the cow-calf behavior from the expulsion of the calf up to separation in a dairy system research, with an average time of 2,489 seconds together, the predominant behavior found by the dam was the intensive licking towards their calf, and secondary particular behaviors were lying down after calving, aggressive behavior upon a surrogate cow, and a following behavior upon separation. On the calf side, the main behaviors were licking the cow, and mobilizing with their two front hooves. Less common behaviors were standing up, reaching the udder, suckling, and looking at her cow upon separation. Moreover, animal-level variables that were associated with these behaviors were found to be parity and calving difficulty. Also, for environmental-level variables, the drop time, calving in the patio, and temperature were associated with these behaviors as well. In general, no significant associations were found for twins, calf gender, and heat index. Lastly, when the future health performance of both animals was analyzed, only the stand-up behavior of the calf was significantly associated with an increased average daily gain weight from birth to weaning, compared to calves that did not stand up. The novel findings presented in this thesis will help dairy management to better understand latent challenges in the industry with an integral approach that includes animal welfare and employee well-being. This study extends the knowledge of cow-calf contact systems by exploring the animal behavior right after calving and up to separation and provides a comprehensive assessment of adaptation, perception, and understanding of precision livestock farming technologies by the dairy employee. The conclusions from this thesis will add to the rapidly expanding field of integrating animal and employee health into integral strategies for current management challenges in the dairy industry.
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 member
To view the abstract, please see the full text of the document.
Open Access
Antimicrobial resistance in the meat industry and the impact of meat animal fecal microbiomes and resistomes on subsequent environments
(Colorado State University. Libraries, 2022) Rice, Emily Ashton, author; Nair, Mahesh N., advisor; Belk, Keith E., committee member; Morley, Paul S., committee member; Noyes, Noelle N., committee member
The discovery of antibiotics for human and animal use is considered one of the greatest medical advancements. However, the widespread use of antibiotics has caused concerns about a potential increase of antimicrobial resistance genes (ARGs) within microbial communities offering the opportunity for consumers to acquire antimicrobial resistant infections through the direct consumption of meat animals or through the environment via manure applications to crop land. Many consumers are becoming increasingly conscious of antibiotic usage labeling when purchasing meat products resulting in animal agriculture being considered a primary contributor for the dissemination of antimicrobial resistance (AMR). Although in recent years many advancements have been made to more fully understand the resistome of production animals preharvest and few post-harvest but, there are minimal studies that fully characterize the resistome of meat animals carcasses throughout the harvest process. Therefore, the purpose of the review (Chapter 2) is to outline opportunities to utilize metagenomic sequencing to pinpoint potential sources of antimicrobial resistance throughout meat processing. This could provide insight to better understand the potential sources of antibiotic resistant bacteria as a result of meat production. As bacteria can acquire ARGs through horizontal gene transfer or mutations, as an evolutionary advantage directly resulting from environmental pressures, the objective of the following study (Chapter 3) was to evaluate the relationships between the fecal resistome of different food animal species (avian, bovine, and porcine), the resistomes of meat from those animals, and resistomes of soil where feces was used as an amendment. Composite fecal samples (n = 20 per species) were collected from each commercial production facility and meat rinsate samples were (n = 20 per species) collected for each species at the time of harvest. After harvest, feces and litter were composted and applied as an amendment on agricultural land. After one growth season, soil samples (n = 20 per species) were collected separately for each species. Additionally, human waste solids were collected from wastewater treatment plants near each animal production operation (n = 14 per species), and soil samples amended with human waste solids were collected (n = 7 per species) from fields in close proximity to the broiler and bovine facilities. DNA was extracted, and the resistome library was prepped using the SureSelectXT reagent kit to prepare samples for target-enriched resistome sequencing targeting ARGs. Reads were analyzed using AMR++ v2 pipeline and sequences were aligned to the MEGARes v2 database to identify ARGs. Richness, evenness, and Shannon's diversity were calculated, and beta-diversity was analyzed using Bray-Curtis dissimilarity distances. Hierarchal clustering was performed using Ward's agglomeration in R. Regardless of species, fecal samples had a greater (P < 0.05) richness and evenness of ARGs compared to both meat and soil samples. For beta diversity, all the sampling types clustered (P < 0.05) individually (feces, meat, and soil) by species. Furthermore, within species each environment was dominated by different classes of ARGs indicating they have different resistomes. When resistance groups medically important for human health by the World Health organization were considered, human waste samples had a greater (P < 0.05) percentage (13%) of medically important resistance groups compared to all animal fecal samples (< 5%) (World Health Organization, 2017). The resistome of feces was richer and more diverse and clustered independently from both meat and soil indicating feces had a more unique resistome across the different species. This suggests that the fecal resistome may not influence meat and amended soil resistomes.
Open Access
Application of biotechnology in agriculture: a bioinformatic and market analysis of novel intervention methods
(Colorado State University. Libraries, 2021) Frazier, Anthony Nathan, author; Yang, Hua, advisor; Metcalf, Jessica, advisor; Martin, Jennifer, committee member; Leach, Jan, committee member
To view the abstract, please see the full text of the document.
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
Assessing the predictive value of dairy facial biometrics for measures of productivity, health, and social dominance
(Colorado State University. Libraries, 2018) McVey, Catherine, author; Pinedo, Pablo, advisor; Grandin, Temple, committee member; Fosdick, Bailey, committee member; Maunsell, Fiona, committee member
To view the abstract, please see the full text of the document.
Open Access
Assessment of rapid evaporative ionization mass spectrometry (REIMS) to characterize beef quality and the impact of oven temperature and relative humidity on beef
(Colorado State University. Libraries, 2018) Gredell, Devin, author; Woerner, Dale, advisor; Belk, Keith, committee member; Engle, Terry, committee member; Prenni, Jessica, committee member; Heuberger, Adam, committee member
The objective of experiment 1 was to evaluate the ability of rapid evaporative ionization mass spectrometry (REIMS) to predict beef eating quality characteristics. Striploin sections (5 cm in thickness; N = 292) from 7 beef carcass types (Select, Low Choice, Top Choice, Prime, Dark Cutter, Grass-fed, and Wagyu) were collected to achieve variation in fat content, sensory attributes, tenderness, and production background. Sections were aged for 14 d, fabricated into 2.54 cm thick steaks, and frozen until analysis. Trained descriptive panel rated tenderness, flavor, and juiciness attributes for sensory prediction models. Slice shear force (SSF) and Warner-Bratzler shear force (WBS) values were measured to predict tenderness classifications. A molecular fingerprint of each sample was collected via REIMS to build prediction models. Models were built using 80% of samples that were selected randomly for this purpose and tested for prediction accuracy using the remaining 20%. Partial least squares (PLS) discriminant analysis was used as a dimension reduction technique before building a linear discriminant analysis (LDA) model for classification. When Select and Low Choice samples, as well as Top Choice and Prime samples, were combined, balanced prediction accuracy reached 83.8%. Slice shear force and WBS tenderness classifications (tough vs tender) were predicted with 75.0% and 70.2% accuracy, respectively. Sensory models were built to assign samples into positive and negative classifications based on either all sensory attributes (i.e., tenderness, juiciness, and flavor) or only flavor attributes. Overall sensory class was predicted with 75.4% accuracy and flavor class with 70.3%. With future fine-tuning, these data suggest that REIMS produces a metabolic fingerprint to provide a method to meaningfully predict numerous beef quality attributes in an on-line application. The objective of the second study was to evaluate the roles of cooking rate and relative humidity on sensory development of beef strip steaks. Thirty USDA Choice beef strip loins were collected from a commercial packing facility. Each strip loin was cut into steaks and randomly assigned to 1 of 6 cooking methods utilizing 2 oven temperatures (80°C and 204°C) and 3 levels of relative humidity [zero (ZH), mid (MH), and high (HH)]. Cooked steaks were used to evaluate internal and external color, Warner-Bratzler and slice shear force, total collagen content, protein denaturation, and trained sensory ratings. Relative humidity greatly reduced cooking rate, especially at 80°C. Steaks cooked at 80°C-ZH had the greatest (P < 0.01) cook loss of all treatments, and cook loss was not affected (P > 0.05). Steaks cooked at 80C-ZH appeared the most (P < 0.01) well-done and had the darkest (P > 0.01) surface color. Total collagen was greatest (P < 0.01) in steaks cooked with ZH, regardless of oven temperature. Myosin denaturation was not affected (P > 0.05) by treatment. Increased (P = 0.02) sarcoplasmic protein denaturation was observed with ZH and MH, while increased (P = 0.02) actin denaturation was observed only with ZH. Oven temperature did not influence (P > 0.05) protein denaturation. Trained panelists rated steaks most tender (P < 0.01) when cooked at 80°C and with ZH and MH. Humidity did not affect (P > 0.05) juiciness at 204°C; however, MH and HH produced a juicier (P < 0.01) steak when cooked at 80°C. Humidity hindered (P < 0.01) the development of beefy/brothy and brown/grilled flavors but increased (P = 0.01) metallic/bloody intensity. Lower oven temperatures and moderate levels of humidity could be utilized to maximize tenderness, while minimally affecting flavor development.
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
Association between patterns of body condition score during early lactation and conception rate in dairy cows
(Colorado State University. Libraries, 2021) Klug, Bailey, author; Pinedo, Pablo, advisor; Salman, Mo, committee member; Ahola, Jason, committee member
The installation of precision farming technology includes the utilization of image biometrics to calculate body condition scores (BCS) in Holstein cattle. Body condition scores help dairy operations to individually estimate energy reserves for each animal, based on subcutaneous fat found throughout the body but more specifically along the spine and the pelvis. Body condition scoring was originally a visual task performed by trained personnel that required specialized training and was often subjective. With the installation of a new automated system that has been validated (DeLaval Body Condition Scoring BCS™), BCS has become more accessible and flexible as a herd management tool. The hypothesis of this study was that low BCS, or a loss in BCS, during early lactation would reduce the rate of conception at multiple artificial inseminations (AI) increasing the number of days to pregnancy. Therefore, the overall objective of this research was to evaluate the association between BCS dynamics and the probability of conception at multiple AI. In chapter 1, a brief literature review about the challenges during the transition period, fertility, and BCS is presented. Chapter 2 is focused on the association between BCS and BCS changes (∆BCS) at multiple time points post-parturition and conception at first AI, while chapter 3 analyzed subsequent breedings up to fourth AI. This prospective observational study was performed on a single dairy operation in Windsor, Colorado, USA with a population of 2,885 Holstein cows including 1,460 primiparous and 1,425 multiparous cows. Study cows were housed in a free stall, cross-ventilated barn and milked three times per day. For study 1, automatic BCS was recorded using the DeLaval Body Condition Scoring BCS™. The records of BCS were gathered at 7, 21, 35, 49, and 60 d in milk (DIM) and on the d of first AI (dAI1). A 5-point scale was used to record BCS with 0.1 intervals. The categorization of BCS was defined as low (L; < mean - 1 SD), intermediate (M; mean ± 1 SD) and high (H; > mean + 1 SD). Changes in BCS were also categorized as no loss (NL; ΔBCS ≥ 0 points) and loss (Los; ΔBCS < 0 points). Multivariate logistic regression models were used to estimate the effect of explanatory variables on conception as a binary outcome. Additionally, a cox regression analysis with hazard ratios were used along with frequency analysis to further visualize the data. The overall conception rate at first AI was 30.1% (34.6 and 25.5% in primiparous and multiparous cows, respectively). Low BCS was associated with lower conception rate to first AI, while loss of BCS resulted in greater days to conception. The same study design was applied in chapter three; however, BCS records were gathered at 7, 30, and 60 DIM, and at dAI1, on the day of second AI (dAI2), third AI (dAI3), and fourth AI (dAI4). Low BCS during early lactation resulted in lower odds of pregnancy at multiple AI. Logistic regression analyses of ∆BCS also showed cows that lost BCS had greater odds of pregnancy at different inseminations. The likelihood that cows will conceive concurrent with a loss in BCS was greater across multiple AI compared to cows that did not lose BCS. The overall success of pregnancy was 27.8% at second AI (pAI2), 21.4% at third AI (pAI3), and 16.0% at fourth AI (pAI4). In conclusion, low BCS were associated with lower conception rates at AI. Furthermore, a loss in BCS were associated with greater number of days from parturition to conception to first AI However, a loss in BCS was associated with greater conception at second, third, or fourth AI. Monitoring daily automatic BCS provides potential for assessing future fertility of dairy cows.
Open Access
Attitudes and competencies of third year veterinary students towards their role as an animal welfare advocate and attitudes towards pain and pain mitigation practices in beef and dairy cattle in the United States by veterinarians and producers
(Colorado State University. Libraries, 2019) Johnstone, Ellizabeth Charlotte Spencer, author; Edwards-Callaway, Lily, advisor; Pinedo, Pablo, committee member; Ahola, Jason, committee member; Stuart, Amy K., committee member
Although leading veterinary organizations emphasize the importance of animal welfare knowledge, there exists a gap in current veterinary student animal welfare education and training. A survey instrument was created to assess third-year Doctor of Veterinary Medicine (DVM) student knowledge of key animal welfare topics, opinions regarding the inclusion of welfare education in the veterinary curriculum, and views on veterinarian responsibilities as advocates. In Spring 2018, Colorado State University added a required animal welfare course to the DVM curriculum. Pre- and post-course paper surveys were distributed to the third-year students enrolled in the animal welfare. One hundred thirty one completed pre-course surveys were collected and 125 completed post-course surveys were collected. Of the pre and post-course surveys collected, 61 were paired with identification codes and utilized for statistical comparison. Results indicated that the course led students to view the inclusion of an animal welfare course in the veterinary curriculum more favorably (p=0.009) and improved their confidence in conducting research on animal welfare topics (p<0.001). The course did not change students' sense of responsibility towards welfare advocacy. Associations were not found between attitudes towards these issues and demographic variables of home community, respondent gender, and track selection (p>0.06). Veterinarians were consistently ranked by students as the most influential member of a community in matters of animal welfare. Future research on the lack of veterinary student knowledge of animal welfare should be done on a national scale to facilitate strategic development of mandatory animal welfare courses in veterinary curricula. Future research should be designed to gain knowledge regarding DVM students' opinions and attitudes regarding effective methods of incorporating animal welfare education into their professional training. The objective of the second survey project was to evaluate the current pain management practices and opinions towards pain management in cattle of beef and dairy veterinarians and producers in the United States. Pain management strategies in livestock have evolved in the last few decades but a variety of obstacles continue to limit improvements in the use of pain mitigation by members of the cattle industries. One such obstacle is the lack of FDA-approved analgesic drugs for use in cattle in the United States which offers limited pain management options to cattle veterinarians and producers. An on-line survey was developed to investigate current use of pain mitigation by cattle veterinarians and producers. The survey was distributed electronically to multiple listservs in Summer 2018 (BEEF Magazine, American Association of Bovine Practitioners, National Milk Producers Federation Farmers Assuring Responsible Management evaluators, Dairy Moms and Dairy Girls Facebook groups; N=46,577). A total of 1,187 (2.5%) surveys were received; 41.9% of respondents identified as producers, 47.9% as veterinarians, and 10.2% as both. Multivariate logistic regression was used for analysis. Veterinarians (OR [95% CI] = 10.2 [7.21-14.4]) and producer-veterinarians (OR [95% CI] = 3.30 [2.02-5.39]) had significantly greater odds of using analgesia than producers in all cattle ages. Summary data suggest that analgesic use changed with cattle age; 57.6% of respondents used pain management in calves <2 months of age, while 71.6% of respondents used pain management in cattle more than 12 months of age. Respondents agreed that "cattle benefit from receiving analgesic drugs" (76.6%) and that "US/USDA/FDA regulations limit my ability to use analgesic drugs in cattle" (64.01%). Fifty-eight percent of respondents indicated their use of pain management had increased in the last 10 years. Data identify impediments to improving pain management practices in cattle. Results indicate the need for education and communication between veterinarians and producers on the necessity of pain management.
Open Access
Beef cattle maternal and terminal economic selection indices
(Colorado State University. Libraries, 2013) Zeng, Xi, author; Enns, Richard Mark, advisor; Thomas, Milton G., committee member; Dalsted, Norman L., committee member
The breeding objective in most livestock operations is to increase profit ability by improving production efficiency. Animals with different purposes are associated with different production systems. The objective of the study is to develop economic selection indices for females and males in three different production systems: maternal, terminal with self-replacement females, and terminal without self-replacement females, based on production characteristics in the intermountain region of the US. Profit equations were constructed to derive economic values under fixed herd size scenario. The parameters used to calculate the cumulative discounted gene expressions (CDGE) and genetic parameters were estimated from 10,007 individual records and 27,165 pedigree records from the Angus herd at the John E. Rouse Beef Improvement Center of Colorado State University. There were 313 sires with an average generation interval of 3.30 years involved in the study, as well as 2,160 dams with an average generation interval of 5.32 years. Sensitivity tests were performed to test the effect of changing production and economic variables on economic selection indices weights. The impacts on selection index for all systems were small with changing production variable. Also, varying economic variables had small effect on selection index of maternal system with correlations among objectives more than 0.80. However, it affects the selection index of two terminal systems a lot with low (-0.05) or even negative (-0.82) correlation between one and another other. The selection responses with considering the cumulative discounted gene expression and based on six economic selection indices were $259.77, $957.10, $93.901, $361.58, $71.81 and $279.30 per generation for females and male in the three production systems, maternal, terminal with self-replacement heifer and terminal without self-replacement heifer, assuming that the selection intensity is one standard deviation. Under all scenarios, selection will lead to increasing profit.