Research Project: Improve Nutrient Management and Efficiency of Beef Cattle and Swine

Location: Nutrition, Growth and Physiology

2018 Annual Report

Objectives
Objective 1: Determine the effects of dietary changes on efficiency of growth and nutrient utilization of beef cattle and swine. Sub-objective 1A: Prediction of dry matter intake from neutral detergent fiber concentration. Sub-objective 1B: Determine the effects of feed additives on feed efficiency. Sub-objective 1C: Evaluate the use of an antibiotic alternative in swine. Objective 2: Improve determination of dynamic changes in nutrient requirements as the animal's physiological status changes to allow for timed nutrient delivery. Objective 3: Use novel forage systems for growing and maintaining beef cattle. Objective 4: Determine metabolic and physiological mechanisms responsible for variation in feed efficiency that is under genetic control. Sub-objective 4A: Evaluate genetic relationships with feed efficiency. Sub-objective 4B: Effects of metabolites and hormones on feed efficiency. Sub-objective 4C: Relationships between mitochondrial function and feed efficiency. Objective 5: Determine the environmental factors that contribute to the variation in feeding behavior, growth, and well-being of livestock. Sub-objective 5A: Novel methods for early detection of illness. Sub-objective 5B: Relationships between swine feeding behavior with feeder size and placement. Sub-objective 5C: Effects of weather on cattle well-being and feeding behavior.

Approach
Feed costs represent the single largest input in both beef and swine production; however, less than 20% of the energy from feed is converted to edible product. Improving the efficiency that feed is converted to animal products has the potential to improve the economic efficiency of animal production while also improving the sustainability of animal agriculture. To maximize feed efficiency the correct profile of nutrients are matched to meet an animal’s needs for its current biological status (growth, pregnancy, lactation, previous nutrient history, and disease). In order to provide the correct profile of nutrients, the nutrient composition of feeds and the dynamic nutrient requirements of the animal must both be identified and then synchronized. There is genetic variation among animals in their ability to utilize feed. Multiple genes are associated with the regulation of feed intake, weight gain, and the utilization of ingested nutrients. Differential expression of these genes results in variation of feed efficiency among animals within populations, and these genetic differences potentially change the nutrient requirements of the animal. Identifying the role of nutrition in regulating gene expression and the mechanisms by which efficient animals utilize nutrients is needed to develop nutrition management strategies. In addition to variation in physiological responses, there is a need to understand genetic and environmental variation in animal feeding behavior that lead to variation in nutrient utilization.

Progress Report
A study using eight steers to determine if feeding ferric citrate would decrease ruminal methane production and improve feed efficiency was performed. Total urine and feces were collected and oxygen, carbon dioxide, and methane exchanges were measured during a 24-hour period using headbox respiration calorimeters. (Objective 1) Finishing cattle (N=768) were used to determine if feeding an essential oil would decrease the presence of liver abscesses at harvest. The livers were scored by visual appraisal at the packing plant and the presence or absence of abscesses were noted. (Objective 1) One-hundred and sixty beef heifers are scheduled for a study to start in August to evaluate how daily dry matter intake changes among diets with different concentrations of neutral detergent fiber. This experiment will allow the development of dry matter intake prediction equations for growing replacement heifers while grazing forages. (Objective 1) Lactobacillus acidophilus fermentation products (LAFP) were evaluated as an alternative to antibiotics in nursery pig diets. Pigs (N=825) were weaned from the sow and allowed to consume one of 3 diets during the nursery phase of production (control diets, control diets + antibiotics, or control diets + LAFP). Pigs were evaluated for growth performance, gut health, and antibiotic resistance genes. (Objective 1) Rumen fluid samples have been collected on 30 cows and 30 calves three times since calves have been born. Blood samples were collected from the calves at each time point and milk samples were collected from the cows at two of the time points (Objective 2). Growth data and reproductive tract data was collected on 120 heifers grazing corn stalks and cover crops. Performance data was collected on 360 cows that had been developed in the corn stalk and cover crop systems (Objective 3). Feed intake and body weight gain has been collected on 320 steers and heifers while on forage diets and also on concentrate diets. Whole blood was collected for hematology analysis and for gene expression analysis on all animals. These data will be used to determine whether gene expression levels in the white blood cells serve as a proxy for feed efficiency status. (Objective 4) Individual feed intake and growth data was collected on 179 five-year-old cows. Feed efficiency phenotypes were previously collected on these same animals as heifers. These data sets, along with data from a second year of animals, will be used to determine the genetic correlation between feed intake and gain at these two production stages. (Objective 4). A total of 980 pigs were phenotyped for feed efficiency through the U.S. MARC swine feed efficiency barn. Pigs that were divergent for feed efficiency were selected for tissue collection. Both barrows and gilts were selected for variation in intake over a ±0.5 SD range of average daily gain. Pigs (n=32, selected by sex x intake) were euthanized and brain, liver, muscle, small intestine, and adipose was collected, snap frozen, and stored for further analysis. (Objective 4) Pigs (n=196) were phenotyped for feed efficiency through the U.S. MARC swine feed efficiency barn. Blood samples were collected on day 0 and 42 of the trial for non-targeted liquid chromatography–mass spectrometry and for transcriptome analysis of the white blood cells. (Objective 4) Five feeding trials (with 200 steers per trial) were conducted to determine genomic differences in cattle that differed in feed intake and body weight gain. RNA sequencing for differential gene expression of 80 of the animals with the highest and lowest gain and feed intake has been performed for muscle, rumen tissue, and the mesenteric fat pad. (Objective 4) DNA was extracted from 1,200 steers with feed efficiency phenotypes for a targeted evaluation of SNP that have been associated with residual feed intake, average daily gain and feed intake. This panel will serve as a validation of markers that have been identified in studies performed in our lab, as well as markers identified from other published studies to better design a panel of markers that are effective for the prediction or selection of animals with superior feed efficiency phenotypes. (Objective 4) A new feeding behavior monitoring system was installed in a 240 head grow-finish facility located at USMARC. The system includes 10 instrumented feeders, and 24 instrumented drinking stations. The system was designed using low frequency RFID readers, 4- and 8-channel multiplexers, custom-made antennas, and microcomputers. Data is summarized in a 10-second interval. Validation of the system with video observations was carried out with 10 focus pigs of the 40 pigs in 2 of the 6 pens. Video data was collected and labelled manually for a 12-hour period. The results indicate an accurate detection of the pigs’ individual feeder visits as well as the total duration of the feeder and drinker visits by the RFID system. (Objective 5) Disruptions in feeding behavior can be indicative of a beginning illness and other impairments of animal well-being. The daily feeding time was collected with a low-frequency RFID system for a total of 2880 pigs over 12 different groups. Illness and subsequent treatments were recorded. The health warnings the model for feeding behavior was compared to the caretaker diagnoses in the reference feeding period. The algorithm detected 62% of severe movement decreases related to an illness event. (Objective 5)

Accomplishments
1. More economical grazing of cover crops produces same feed efficiency as corn silage. Pasture grass availability for cattle grazing is decreasing in the Northern Great Plains; however, there is opportunity to integrate cattle production into cropping or backgrounding systems to provide additional forage availability for producers. The abundance of diverse forage resources in the Plains region provides cattle producers many different options to background calves prior to placing them in a feedlot and finishing them out for meat harvest. A study conducted by ARS scientists at Clay Center, Nebraska, and collaborators at the University of Nebraska evaluated three forage options: corn residue, supplemented with dried distillers grains; late summer planted oat-brassica forage mix; and a corn silage-based diet fed in a drylot. The study included 360 crossbred steers and body weight gain and carcass characteristics were measured on all steers. Average daily gain before feedlot entry (backgrounding), and feed efficiency during finishing on a high concentrate diet, was highest for steers fed in the drylot; however, finishing phase feed efficiencies did not differ between the corn residue and oat-brassica backgrounding treatments. For all diets, rib fat and yield grade did not differ; thus, the potential lower cost of alternative grazing systems could make these backgrounding methods economically competitive for producers in the Plains region.

2. Circulating levels of endocannabinoids are markers for improved performance and feed efficiency. Blood concentration of endocannabinoids, a class of lipid metabolites produced by the body, are positively associated with feed efficiency and leaner carcasses in finishing steers. It is not clear, however, whether animal growth during the finishing period might influence the concentration of endocannabinoids. The objective of this study performed by ARS research scientists at Clay Center, Nebraska, was to quantify the endocannabinoids in plasma during the finishing period and determine their association with production traits and carcass composition in finishing beef calves. Individual intake and gain were measured on 236 calves (n = 127 steers and n = 109 heifers) for 84 days on a finishing ration. Blood samples were collected on day 0 (early), day 42 (mid) and day 83 (late) on feed and endocannabinoids were measured. The level of the endocannabinoid, anandamide (AEA), was higher in more efficient animals at mid to late stages of the finishing period. In addition, AEA concentration was associated with carcass composition in heifers with higher levels of AEA associated with higher hot carcass weight and improved yield grade. Specific circulating endocannabinoids may be useful biomarkers for feed efficiency in beef cattle and carcass composition in beef heifers.

3. Rumen microbiome community profiles are associated with feed efficiency. Literature evaluating the influence of the rumen microbiome composition on feed efficiency in beef cattle is limited. A better understanding of the relationships between the rumen microbial population and body weight gain, feed intake, and feed efficiency is needed. ARS researchers at Clay Center, Nebraska, and collaborators at the University of Nebraska characterized the rumen microbiomes of two large animal cohorts (125 heifers and 122 steers) to identify specific bacterial members associated with feed efficiency traits in beef cattle. Animal cohorts were fed a forage-based diet and a concentrate-based diet, respectively. A rumen sample was obtained from each animal for bacterial community profiling. This innovative study showed that the species and abundance of the microbes present in the rumen account for a large proportion (20%) of the variation in feed efficiency. These data provide insight into the microbial composition that is beneficial to feed efficiency and will now inform future strategies to alter rumen microbial communities to improve feed efficiency in cattle.

4. Shade material affects the reduction of heat stress in cattle. Heat stress has a significant impact on beef production causing an estimated $369 million annual losses, as well as concerns about animal well-being. Providing shade is one management option to mitigate these losses; however, there is little data regarding the efficacy of the materials used for shade structures. ARS researchers at Clay Center, Nebraska, in collaboration with Texas A&M University and Auburn University, evaluated three types of shade materials for feedlot cattle. Thirty-two black Angus heifers were randomly allocated to one of 4 pens for an 8-week summer time period. Each pen was assigned a shade treatment: no shade, fenceline snow fence, 60% Aluminet overhead shade cloth, and 100% overhead shade cloth. Respiration rates were measured, and complete blood counts and cortisol concentrations were assayed. The 60% Aluminet shade cloth and 100% shade cloth produced the best physiological responses; however, cortisol levels were the lowest (most beneficial to the animal) with the 60% Auminet shade cloth. These results indicate a 60% shade cloth is the most effective at reducing animal stress. Further research using 60% shade cloth in industry sized pens over several years will be needed to assess the potential performance advantage.

5. Compensatory gain gene expression changes were identified in mature cows. In beef production systems beef cows typically experience periods of nutrient restriction, followed by an abundance of nutrients and the animal’s tissues and organs must respond and adjust to nutrient availability; however, the molecular responses of these tissues to these nutritional extremes have not been well studied. In this study, conducted by ARS scientists at Clay Center, Nebraska, and collaborators at the University of Wyoming, mature cows were subjected to feed restriction followed by ad libitum feed. Changes in biological responses, via gene expression, were identified in the adipose tissue of beef cows with high and low body weight gain during the ad libitum feeding period. Results from the study identified biological pathways that underlie weight gain during times of abundance of feed after a restricted diet. The pathways critical to readjustment to an abundance of feed included mitochondrial energy production pathways, fatty acid metabolism, and propanoate metabolism pathways. These data also provide a platform for continued work to identify key genes and associated biological functions in adipose tissue associated with divergence in weight gain in beef cows. The ability to identify animals that will respond with greater compensatory gain upon refeeding will help producers improve production efficiencies and ensure animal health and well-being based on nutrient availability.

6. Biomarkers in the small intestine provide insight into cattle feed efficiency. The influence and role of the small intestine in feed efficiency and growth of beef cattle has not been well defined. The majority of research on the influence of the gastrointestinal tract on growth and feed efficiency has focused on the rumen. It has been proposed; however, that the small intestine could be equally as important in grain fed feedlot cattle, as there is less reliance on fiber digestion for energy in the small intestine as compared to the rumen. ARS scientists at Clay Center, Nebraska, used next generation RNA sequencing technology to explore physiological differences in the mid-small intestine (jejunum) of cattle with average feed intake and relatively fast or slow growth rates. A total of 64 genes were found to be expressed at different levels between the 2 groups of 8 cattle. The genes that were upregulated in the faster growing cattle (54 genes) are largely related to digestion and absorption. If the differences in gene expression translate into biologically functional changes, it could indicate that the faster growing cattle are better at digesting starch into glucose, absorbing glucose, digesting protein, and/or protecting against oxidative stress and microbial infection. Results from this study show that it may be possible to select animals that have an improved genetic ability to digest dietary components to achieve a greater level of growth and feed efficiency.

7. Gene expression differences identified in the skeletal muscle of steers that vary in feed utilization efficiency. Gene expression studies suffer from issues with reproducibility among different populations of cattle. The purpose of this study was to discover differentially expressed genes that were robust for feed intake and gain across a large segment of the cattle industry. ARS researchers at Clay Center, Nebraska, evaluated the gene expression of muscle tissue from 80 steers with high and low body weight gain and feed intake collected over five different seasons. Variation among differentially expressed genes, suggests that environment and breed may play large roles in the expression of genes in the muscle of beef cattle that are associated with feed efficiency. Meta-analyses of transcriptome data from groups of animals over multiple cohorts is an approach that can be used to elucidate the genetics contributing these types of biological phenotypes. A meta-analysis identified 171 genes, several of which were involved in the biological functions of mitochondrial energy production and oxidative stress. These genes may serve as biological markers that could be useful across populations of beef cattle for the selection of animals with higher body weight gain and lower feed intake.

8. Circulating glucose as a measure of body weight gain in cattle. Measures of stress and metabolism have been shown to be indicative of growth and the development of bovine respiratory disease (BRD) of beef cattle. It would be beneficial to beef producers to be able to measure these markers earlier in life so that management strategies could be modified to improve both production and animal health and well-being. ARS researchers at Clay Center, Nebraska, conducted an experiment to determine if measurement of serum cortisol, lactate, and glucose in 450 beef calves prior to, or at weaning, would be predictive of average daily body weight gain (ADG) and/or development of BRD. Serum glucose at weaning tended to be predictive of lung lesions and cattle that were diagnosed with BRD tended to have lower pre-weaning glucose concentrations. Pre-weaning serum glucose was also highly associated with pre-weaning and post-weaning ADG and explained 3.2% of the variation in gain. While pre-weaning stress measures were not significantly predictive for the development of BRD, it does appear that glucose metabolism early in life can be predictive of growth potential of beef cattle. Thus, serum glucose may be an early biomarker for ADG in beef cattle, and glucose levels at weaning may also have utility for predicting illness.

9. Monensin does not improve feed utilization of pregnant beef heifers. Improvements in beef cattle feed efficiency can be obtained by reducing the amount of inefficient outputs, such as methane, that an animal produces. Monensin has been reported to reduce methane production early in the feeding period in dairy and feedlot cattle. But, the effect of Monensin has not been reported when fed to bred heifers in confinement to maintain body tissue and growth of reproductive tissues. The objective of this study performed by ARS researchers at Clay Center, Nebraska, and Texas A&M University, was to determine if feeding monensin would improve diet digestion, energy and nutrient balance in bred heifers receiving a limit-fed corn stalk-based diet. Sixteen pregnant heifers were randomly assigned to a treatment group of either no monensin or 150 milligrams of monensin per day. Dry matter intake and fiber digestion was measured. Dry matter intake increased to account for increasing fetal growth requirements, but did not differ between treatments. The use of monensin for heifers fed in drylot did not improve digestibility, nutrient, or energy balance; thus, adding monensin to limit-fed, corn stalk-based diets did not affect feed utilization of confined heifers.

10. Butyrate treatment in the small intestine improved nutrient uptake in sheep. Butyrate is a natural compound present at low concentrations in the small intestine of ruminants such as lambs and cattle. Supplemental butyrate supplied to the small intestine has previously been shown to improve growth and nutrient utilization. One previous study with lambs showed that an infusion of butyrate into the abomasum increased the uptake of glucose, glutamine, glutamate, and oxygen by the portal-drained viscera, which indicated a potential upregulation of glycolysis and possibly tissue growth. A study conducted by ARS researchers at Clay Center, Nebraska, determined if the changes in nutrient utilization from butyrate treatment was associated with changes in gene expression that reflect an improvement in nutrient uptake in the duodenum. Using a gene microarray, it was determined that 230 genes were differentially expressed in the duodenum. Pathway analysis of the genes differentially expressed revealed that several nutrient metabolism and nutrient shuttling pathways were up-regulated by the butyrate treatment. These data support the hypothesis that butyrate treatment increased nutrient uptake in the small intestine by an increase in the expression of genes related to higher oxygen and glucose uptake in the duodenum. This study indicates that butyrate treatment improves gut health and nutrient uptake, which is likely to improve feed efficiency.

11. Biological variation in the muscle of mice lacking CAPN1 – implications for meat animal production. The calpain proteins, which include CAPN1, are protein degradation enzymes that play a role in the muscle tissue growth, which is the difference between protein synthesis and degradation. To better understand the biological function of CAPN1, the gene expression of mice lacking CAPN1 was studied. ARS researchers at Clay Center, Nebraska, sequenced the gene transcripts in the muscle tissues of 18 mice with and without the CAPN1 gene to determine which genes were over- or under-expressed. A total of 55 differentially expressed genes were identified among mice lacking the CAPN1 gene. The genes identified in this study may be potential ortholog targets to promote muscle growth in livestock species.

12. Mechanisms adapted by Bos indicus cattle to reduce heat stress. Bos taurus breeds of cattle are more susceptible to heat stress than Bos indicus breeds. Heat stress is a source of economic loss in hot climates and during periods of seasonal heat stress, as well as a concern for animal health and well-being. This study was conducted in Brazil at the Sao Paulo State University as a collaborative effort between by ARS researchers at Clay Center, Nebraska, and researchers at Sao Paulo State University to gain a better understanding of the patterns of thermoregulation of Bos indicus Nellore bulls. Both weather and physiological measures were assessed for Nellore bulls. Temperature ranges were between 21-31°C. At temperatures above 29°C, sweating was the principal way to maintain the thermal equilibrium. This study further determined that Nellore bulls use less energy to regulate body temperature, than Bos taurus breeds which improves heat tolerance providing them better adaptation to warm climates than Bos taurus animals. A better understanding of the mechanisms of thermal regulation leading to heat tolerance will allow quicker evaluation of other heat tolerant breeds.

Review Publications
Cunningham, H.C., Cammack, K.M., Hales Paxton, K.E., Freetly, H.C., Lindholm-Perry, A.K. 2017. Microarray analysis of subcutaneous adipose tissue from mature cows with divergent body weight gain after feed restriction and realimentation. Data in Brief. 16:303-311. https://doi.org/10.1016/j.dib.2017.10.016.
Hemphill, C.N., Wickersham, T.A., Sawyer, J.E., Brown-Brandl, T.M., Freetly, H.C., Hales, K.E. 2018. Effects of feeding monensin to bred heifers fed in a drylot on nutrient and energy balance. Journal of Animal Science. 96(3):1171-1180. https://doi.org/10.1093/jas/skx030.
Artegoitia, V.M., Foote, A.P., Tait Jr, R.G., Kuehn, L.A., Lewis, R.M., Wheeler, T.L., Freetly, H.C. 2017. Endocannabinoid concentrations in plasma during the finishing period are associated with feed efficiency and carcass composition of beef cattle. Journal of Animal Science. 95(10):4568-4574. https://doi.org/10.2527/jas2017.1629.
Berry, E.D., Wells, J.E., Varel, V.H., Hales, K.E., Kalchayanand, N. 2017. Persistence of Escherichia coli O157:H7 and total Escherichia coli in feces and feedlot surface manure from cattle fed diets with or without corn or sorghum wet distillers grains with solubles. Journal of Food Protection. 80(8):1317-1327. https://doi.org/10.4315/0362-028X.JFP-17-018.
Brown-Brandl, T.M., Chitko-McKown, C.G., Eigenberg, R.A., Mayer, J.J., Welsh, T.H., Davis, J.D., Purswell, J.L. 2017. Physiological responses of feedlot heifers provided access to different levels of shade. Animal. 11(8):1344-1353. https://doi.org/10.1017/S1751731116002664.
Cox-O'Neill, J.L., Hales, K.E., Ulmer, K.M., Rasby, R.J., Parsons, J., Shackelford, S.D., Freetly, H.C., Drewnoski, M.E. 2017. The effects of backgrounding system on growing and finishing performance, and carcass characteristics of beef steers. Journal of Animal Science. 95(12):5309-5319. https://doi.org/10.2527/jas2017.1934.
Foote, A.P., Jones, S., Kuehn, L.A. 2017. Association of preweaning and weaning serum cortisol and metabolites with ADG and incidence of respiratory disease in beef cattle. Journal of Animal Science. 95(11):5012-5019. https://doi.org/10.2527/jas2017.1783.
Foote, A.P., Keel, B.N., Zarek, C.M., Lindholm-Perry, A.K. 2017. Beef steers with average dry matter intake and divergent average daily gain have altered gene expression in the jejunum. Journal of Animal Science. 95(10):4430-4439. https://doi.org/10.2527/jas2017.1804.
Foote, A.P., Zarek, C.M., Kuehn, L.A., Cunningham, H.C., Cammack, K.M., Freetly, H.C., Lindholm-Perry, A.K. 2017. Effect of abomasal butyrate infusion on gene expression in the duodenum of lambs. Journal of Animal Science. 95(3):1191-1196. https://doi.org/10.2527/jas2016.1022.
Hales, K.E., Wells, J., Berry, E.D., Kalchayanand, N., Bono, J.L., Kim, M.S. 2017. The effects of monensin in diets fed to finishing beef steers and heifers on growth performance and fecal shedding of Escherichia coli O157:H7. Journal of Animal Science. 95(8):3738-3744. https://doi.org/10.2527/jas2017.1528.
Hayes, M.D., Brown-Brandl, T.M., Eigenberg, R.A., Kuehn, L.A., Thallman, R.M. 2017. Evaluating a new shade for feedlot cattle performance and heat stress. Transactions of the ASABE. 60(4):1301-1311. https://doi.org/10.13031/trans.12104.
Kim, M., Kuehn, L.A., Bono, J.L., Berry, E.D., Kalchayanand, N., Freetly, H.C., Benson, A.K., Wells, J. 2017. The impact of the bovine faecal microbiome on Escherichia coli O157:H7 prevalence and enumeration in naturally infected cattle. Journal of Applied Microbiology. 123:1027-1042. https://doi.org/10.1111/jam.13545.
Lindholm-Perry, A.K., Artegoitia, V.M., Miles, J.R., Foote, A.P. 2017. Expression of cytokine genes and receptors in white blood cells associated with divergent body weight gain in beef steers. AGRI GENE. 6:37-39.. https://doi.org/10.1016/j.aggene.2017.09.005.
Lindholm-Perry, A.K., Cunningham, H.C., Kuehn, L.A., Vallet, J.L., Keele, J.W., Foote, A.P., Cammack, K.M., Freetly, H.C. 2017. Relationships between the genes expressed in the mesenteric adipose tissue of beef cattle and feed intake and gain. Animal Genetics. 48(4):386-394. https://doi.org/10.1111/age.12565.
Lu, Y., Hayes, M.D., Stinn, J.P., Brown-Brandl, T.M., Xin, H. 2017. Evaluating ventilation rates based on new heat and moisture production data for swine production. Transactions of the ASABE. 60(1):237-245. doi:10.13031/trans.11888.
Reynolds, J.G., Foote, A.P., Freetly, H.C., Oliver, W.T., Lindholm-Perry, A.K. 2017. Relationships between inflammation- and immunity-related transcript abundance in the rumen and jejunum of beef steers with divergent average daily gain. Animal Genetics. 48(4):447-449. doi:10.1111/age.12546.
Tedeschi, L.O., Galyean, M.L., Hales, K.E. 2017. Recent advances in estimating protein and energy requirements of ruminants. Animal Production Science. 57:2237-2249. https://doi.org/10.1017/AN17341.
Wells, J.E., Berry, E.D., Kim, M., Shackelford, S.D., Hales, K.E. 2017. Evaluation of commercial ß-agonists, dietary protein, and shade on fecal shedding of Escherichia coli O157:H7 from feedlot cattle. Foodborne Pathogens and Disease. 14(11):649-655. https://doi.org/10.1089/fpd.2017.2313.
Carol De Melo Costa, C., Sandro Campos Maia, A., Brown-Brandl, T.M., Chiquitelli Neto, M., De Franca Carvalho F, O. 2018. Thermal equilibrium of Nellore cattle in tropical conditions: an investigation of circadian pattern. Journal of Thermal Biology. 74:317-324. https://doi.org/10.1016/j.jtherbio.2018.04.014.
Cross, A.J., Keel, B.N., Brown-Brandl, T.M., Cassady, J.P., Rohrer, G.A. 2018. Genome-wide association of changes in swine feeding behaviour due to heat stress. Genetics Selection Evolution. 50:11. https://doi.org/10.1186/s12711-018-0382-1.
Derner, J.D., Briske, D., Reeves, M., Brown-Brandl, T.M., Meehan, M., Blumenthal, D.M., Travis, W., Augustine, D.J., Wilmer, H.N., Scasta, J. 2017. Vulnerability of grazing and confined livestock in the Northern Great Plains to projected mid- and late-twenty-first century climate. Climatic Change. https://doi.org/10.1007/s10584-017-2029-6.
Melchior, E.A., Hales, K.E., Lindholm-Perry, A.K., Freetly, H.C., Wells, J.E, Hemphill, C.A., Wickersham, T.A., Sawyer, J.E., Myer, P.R. 2018. The effects of feeding monensin on rumen microbial communities and methanogenesis in bred heifers fed in a drylot. Livestock Science. 212:131-136. https://doi.org/10.1016/j.livsci.2018.03.019.
Oliver, W.T., Keel, B.N., Lindholm-Perry, A.K., Horodyska, J., Foote, A.P. 2018. The effects of Capn1 gene inactivation on the differential expression of genes in skeletal muscle. Gene. 668:54-58. https://doi.org/10.1016/j.gene.2018.05.040.
Paz, H.A., Hales Paxton, K.E., Wells, J., Kuehn, L.A., Freetly, H.C., Berry, E.D., Flythe, M.D., Spangler, M.L., Fernando, S. 2018. Rumen bacterial community structure impacts feed efficiency in beef cattle. Journal of Animal Science. 96(3):1045-1058. https://doi.org/10.1093/jas/skx081.
Tait Jr, R.G., Cushman, R.A., McNeel, A.K., Casas, E., Smith, T.P.L., Freetly, H.C., Bennett, G.L. 2018. µ-Calpain (CAPN1), calpastatin (CAST), and growth hormone receptor (GHR) genetic effects on Angus beef heifer performance traits and reproduction. Theriogenology. 113:1-7. https://doi.org/10.1016/j.theriogenology.2018.02.002.
Watson, A.K., Hales, K.E., Hersom, M.J., Horn, G.W., Wagner, J.J., Krehbiel, C.R., McCurdy, M.P., Erickson, G.E. 2018. Mineral retention of growing and finishing beef cattle across different production systems. Professional Animal Scientist. 34:250-260. https://doi.org/10.15232/pas.2017-01672.
Schweer, K.R., Kachman, S.D., Kuehn, L.A., Freetly, H.C., Pollak, E.J., Spangler, M.L. 2018. Genome-wide association study for feed efficiency traits using SNP and haplotype models. Journal of Animal Science. 96:2086-2098. https://doi.org/10.1093/jas/sky119.
Thallman, R.M., Kuehn, L.A., Snelling, W.M., Retallick, K.J., Bormann, J.M., Freetly, H.C., Hales, K.E., Bennett, G.L., Weaber, R.L., Moser, D.W., MacNeil, M.D. 2018. Reducing the period of data collection for intake and gain to improve response to selection for feed efficiency in beef cattle. Journal of Animal Science. 96:854–866. https://doi.org/10.1093/jas/skx077.
Keel, B.N., Zarek, C.M., Keele, J.W., Kuehn, L.A., Snelling, W.M., Oliver, W.T., Freetly, H.C., Lindholm-Perry, A.K. 2018. RNA-seq meta-analysis identifies genes in skeletal muscle associated with gain and intake across a multi-season study of crossbred beef steers. BMC Genomics. 19:430. https://doi.org/10.1186/s12864-018-4769-8.