Brief Summary of Minutes of Annual Meeting

Multi-State Project W2010  

Molecular Mechanisms that Regulate Efficiency of Feed Utilization in Beef Cattle.

Annual Meeting 2016 – Minutes.

Minutes for July 21^st 2016, W2010 multistate group meeting held at Salt Lake City, Utah.

The meeting was opened by Dr. Michael Davis at 7:00 p.m.

Members Present – Michael Davis (Ohio State U), Phillip Meyer (U Tennesse), Stephanie Hansen (Iowa State U), Roberto Sainz (UC Davis), Samodha Fernando (U Nebraska), James Oltjen (UC Davis) and Jennifer Thompson (Montana State U).

Guests Present - Casey Dykier (graduate student - UC Davis), Emily Andreini (graduate student - - UC Davis),

Agenda:

Business Meeting:

New Officers – Since the W2010 group did not meet last year, Michael Davis called the meeting to order and asked for any volunteers for the position of President and Secretary for 2017. Dr. Stephanie Hansen volunteered to take the President position for 2017 and was unanimously elected. For the secretary position, Dr. Roberto Sainz volunteered and was unanimously elected.

Feed efficiency symposium – The members discussed about having a feed efficiency symposium in 2017. Dr. Michael Davis reported that he already put in an application to have the symposium at the 2017 Midwest Animal science meetings. He had also contacted the beef, swine and dairy feed efficiency grant recipients to work together on this symposium. It was decided to have a join symposium with the feed efficiency grant recipients.

The Business meeting was followed by presentation of the station reports.

California – Roberto Sainz

Iowa – Stephanie Hansen

Montana – Jennifer Thomson

Nebraska – Samodha Fernando

Ohio – Mike Davis

Tennessee – Phillip Meyer

Adjournment: 10:00 p.m.

W2010 Annual Report 2016

Summary

Over the last year the W2010 project has contributed greatly towards enhancing the efficiency of feed utilization and increasing scientific knowledge of beef cattle feed efficiency. The worked performed by the W2010 multistate research group has been presented at national and regional scientific meetings. Additionally, graduate student training and partnerships with the industry has been a main focus of the group. The multidisciplinary group has focused their research on efficiency, the interactions between diet and microbiota composition in the feed efficiency phenotype and Genome wide association studies. More detailed information on each area is described in individual station reports.

Outputs: Data outputs from experiments conducted by members of W2010 are described below. Committee members have submitted collaborative grant proposals. Several new collaborations have been established among the new members. Additional outputs of the W2010 group include, the planning of a feed efficiency symposium for 2017. Additionally, 16 peer-reviewed journal articles, 17 conference proceedings papers, 10 scientific abstracts, 4 experiment station/extension reports and 1 thesis dissertation have been published by this group on related topics during the past year  (listed in Publications). The group has also mentored graduate and undergraduate students and have provided opportunities for undergraduate research. As a result University of California-Davis graduate student Katherine C. Dykier presented the paper “Performance and net energy in high and low RFI beef cattle on restricted intake” at the California Animal Nutrition Conference in May, 2016 and won first prize for best graduate student paper and Iowa State graduate student Russell, J. R., won 2^nd place in the Ph.D. poster competition for his paper “Influence of growing phase feed efficiency classification on finishing phase growth performance and carcass characteristics of beef steers fed different diet types”.

Activities:  

University of California-Davis: 

The California performed An extensive performance trial was recently concluded, in which 98 calves were fed individually and their intake, diet selection, gain, body composition, metabolic rate and microbiota were examined. Analyses are ongoing. This project has provided opportunities for training of 2 graduate and 12 undergraduate student assistants. Students participated in experimental design, care and handling of animals, sample collection and processing, and data analyses. Results of this research have been presented to stakeholders through Cooperative Extension workgroup meetings and cattle producer workshops.

Experimental data analyzed to date indicate that compared to less efficient animals, more efficient cattle tend to a) deposit less fat and more lean tissue; b) have lower maintenance energy requirements; and c) possess less metabolic plasticity when subjected to a restricted feeding regime.

Iowa State University: 

The Iowa experiment station conducted an experiment to understand biological sources of variation in efficiency of feed utilization as quantified by traits such as RFI.

Feed efficiency (FE) can vary between individuals but sources of variation are not well characterized. Oxidative stress is among the biological mechanisms believed to contribute to variation. The objective of this study was to evaluate the relationship between FE, antioxidant activity, and oxidative stress in feedlot steers representing phenotypic extremes for FE. Crossbred beef steers (n = 181) fed 70­d growing phase (GP) whole­shell corn–based (G­Corn) or rye baleage and soybean hull–based (G­Rough) diets in GrowSafe bunks at the University of Missouri were shipped to Iowa State University where the 12 most feed efficient (HFE) and 12 least feed efficient (LFE) steers from each diet (n = 48; 467 kg [SD 51]) were selected for evaluation. Steers received diets similar to GP diets, and 3 d after arrival, blood was sampled to evaluate antioxidant activity and oxidative stress markers for the GP following transit. Steers were transitioned to finishing phase (FP) cracked corn­based (F­Corn) or dried distillers’ grains and soybean hull–based (F­Byp) diets, and on FP d 97, blood samples for the FP were collected. Data for the GP were analyzed as a 2 × 2 factorial, and data for the FP were analyzed as a 2 × 2 × 2 factorial using PROC MIXED of SAS. No GP diet × FP diet, FP diet × FE group, or 3­way interactions were noted (P ≥ 0.11) for FP measures. Steers fed the G-Rough diet had greater (P = 0.04) GP plasma protein carbonyl concentrations. During the GP, HFE steers had greater (P ≤ 0.04) protein carbonyl and ratio of oxidized:reduced blood lysate glutathione concentrations than LFE steers. There were GP diet × FE group interactions (P ≤ 0.03) during the GP and FP. During the GP, total blood lysate superoxide dismutase (SOD) activity was greater (P ≤ 0.03) in G-Rough/LFE steers than in G-Rough/ HFE and G­Corn/LFE steers; G­Corn/HFE steers were intermediate. The G­Rough/LFE steers had greater (P < 0.04) glutathione peroxidase (GPX) activity than other groups and greater (P = 0.03) plasma malondialdehyde concentrations than G­Corn/LFE steers. During the FP, the G­Rough/LFE steers had greater (P ≤ 0.04) GPX activity than G­Rough/HFE and G­Corn/LFE steers; G­Corn/HFE steers were intermediate. The F­Byp diet had greater (P < 0.01) protein carbonyl than the F­Corn diet, and no other FP diet effects were noted (P ≥ 0.3) for any FP measures. The GP diet and FE groups had stronger relationships with antioxidant activity and oxidative stress markers measured for the GP than for the FP. Overall, antioxidant activity may play a role in FE as LFE steers, driven largely by G­Rough/LFE steers, had greater SOD activity and GPX activity than HFE steers, potentially using a greater proportion of energy otherwise available for tissue accretion.

A 5­yr study was conducted using 985 crossbred steers (464 kg [SD 32]) fed in 6 separate, replicated groups to determine the influence of growing phase (GP) feed efficiency (FE) classification and diet type on finishing phase (FP) FE of steers. During the GP at the University of Missouri, steers were fed either a whole shell corn–based diet (G­Corn; 528 steers) or a roughage­based diet (G­Rough; 457 steers) using GrowSafe feed bunks to measure DMI for 69 to 89 d. At the end of the GP, steers were ranked by residual feed intake (RFI) within diet, shipped to Iowa State University, and blocked into FP pens (5 to 6 steers/pen) by GP diet and RFI rank (upper, middle, or lower one­ third). Steers were transitioned to either FP cracked corn– or byproduct­based diets and fed until 1.27 cm backfat was reached. After completion of the sixth group, average GP G:F within GP diet was calculated for each FP pen (168 total pens) using GP initial BW as a covariate (G­Corn: 0.207 [SD 0.038]; G­Rough: 0.185 [SD 0.036]). Pens were classified as highly feed efficient (HFE; >0.5 SD from the G:F mean; 58 pens), mid feed efficient (MFE; ±0.5 SD from the G:F mean; 60 pens), or lowly feed efficient (LFE;

Findings: More work is needed to support these findings, but our initial work suggests that the type of diet fed to cattle during the feed efficiency assessment may influence which cattle are being selected as high versus low feed efficiency. This may be more important in roughage-based diets where gut fill and voluntary feed intake are large drivers of feed efficiency than in grain-based diets where chemostatic feedback dominates. 

Impacts: Biological factors affecting feed efficiency in cattle are not fully understood and these data suggest that antioxidant capacity may contribute to differences in feed efficiency among cattle. The large feed efficiency trial conducted over multiple years suggests that feed efficiency is repeatable across growing and finishing phases and that differences in diet type may influence how cattle are ranked as feed efficient compared to others.

Work Planned for Next Year: Research in the coming year will focus on the impact of trace mineral status of cattle and subsequent influence on feed efficiency, with a particular emphasis on zinc nutrition.

Montana State University:

Montana State University conducted the following studies that fit the objectives of the W2010 multistate project:

1. To understand biological sources of variation in efficiency of feed utilization.

Current study evaluating individual animal variation in extreme high and extreme low RFI growing lambs. High and low RFI animals are identified after 42 day feeding trial. Evaluated the use of a human triaxial pedometer for measuring activity level in sheep (Manuscript submitted). Found differences in body composition for lambs divergent for RFI. More efficient lambs had heavier rumen and lung weights than inefficient lambs.

Currently evaluating rumen microbiome, rumen histology, NMR serum metabolites and liver, muscle, and adipose gene expression related to divergent RFI class in growing lambs.

1. To discover physiological biomarkers and genetic markers for feed efficiency.

Collaboration with attached reference evaluating predictive power of blood metabolites measured by NMR on prediction of phenotypic variation in RFI in feedlot cattle with Texas A & M to confirm previous results with additional resolution. (result of this group)

Ongoing Research:

1. Hatch Projects – Investigating the underlying physiology of economically important traits in livestock genetic improvement
2. Wildlife Genomics – Bighorn sheep population study, Argali sheep in Kyrgyzstan
3. Feed Efficiency – Sheep study analysis underway
4. Funding for NSF, Wild Sheep Foundation, National Geographic for genotyping of Rocky Mountain Bighorn Sheep
5. Bair Ranch Foundation Funding for Candidate marker and gene identification in American Simmental Association Carcass Merit Project
6. Bair Ranch Foundation Funding for Gene Expression Profiling in muscle of beef carcasses differing in quality grade.

Recent Outputs:

1. Proceedings papers and presentations at WSASAS meeting, ASAS JAM, Montana State University College of Agriculture Research Report
2. Approximately 2200 DNA samples archived on Bighorn Sheep, Mountain Goat, Cattle, and Sheep
3. Submission of 2016 proposal to AFRI-NIFA Foundational Program A1231: High Throughput Metabolomics to Identify Beef Cattle Metabolic Phenotypes with Resistance to Nutritional Stress 

Ohio State University:

Following studies were conducted at Ohio State University as part of the W2010 project.

Objective 1:  To understand biological sources of variation in efficiency of feed utilization as quantified by traits such as RFI.

Data were collected at the University of Wisconsin, Madison, from 1953 through 1980 from identical and fraternal twin beef and dairy females born in 1953, 1954, 1959, 1964, and 1969, and from crossbred females born as singles in 1974, and their progeny. Numbers of dams that weaned at least 1 calf and were included in the first analysis were 37, 45, and 56 in the 1964, 1969, and 1974 data sets, respectively. Respective numbers of dams that weaned 3 calves and were included in a second analysis were 6, 8, 8, 22, 33, and 33 in the 1953, 1954, 1959, 1964, 1969, and 1974 experiments.    Individual feed consumption was measured at 28-d intervals from the time females were placed on the experiment until 3 calves were weaned or the dams had reached 5 yr of age.  Residual feed intake (RFI) and residual gain (RG) of the heifers that subsequently became the dams in this study were determined based on ADG and DMI from 240 d of age to first calving.  Various measures of cow efficiency were calculated on either a life cycle or actual lifetime basis using ratios of progeny and dam weight outputs to progeny and dam feed inputs.  As expected, residual feed intake was phenotypically independent of ADG and metabolic midweight (MWW), whereas the correlation between RFI and DMI was positive and highly significant (r = 0.59; P < 0.0001).  Feed intake was 9.5% less in low RFI heifers than in high RFI heifers and 8.3% less in medium RFI heifers compared to high RFI heifers.  Residual gain was highly correlated with ADG (r = 0.67; P < 0.0001) and had near 0 correlations with DMI and MWW.  Correlations of DMI, ADG, and MWW with cow efficiency ratios ranged from -0.20 to -0.51 and were generally highly significant, indicating that heifers that ate less, gained less weight, and had smaller MWW from 240 d of age to first calving had superior cow efficiency ratios.  RFI was not significantly correlated with age at puberty or age at calving.  Significant differences among the low, medium, and high RFI groups were not observed for any of the cow efficiency component traits.  RFI was not correlated with milk production during any of the 3 lactations. Results indicated that selection for increased RG would tend to result in earlier ages at puberty and calving along with increased milk production, but would also result in taller and heavier cows.  The RFI and RG of heifers exhibited small favorable correlations with subsequent cow efficiency ratios, indicating that heifers with superior RFI and RG became slightly more efficient cows.

Application of Findings: Results of this study do not indicate any serious antagonisms of postweaning heifer RFI with subsequent cow and progeny performance traits or with life cycle or actual lifetime cow efficiency.   The findings also suggest that selection for increased RG would tend to result in earlier ages at puberty and calving, along with increased milk production, but would also result in taller and heavier cows.

Impacts:Feed constitutes a major input to beef production, and is, in fact, the largest single expense in most commercial beef production enterprises.  Efficiency of feed utilization is, therefore, an obvious candidate for improvement in order to reduce cost of beef production.  Studies conducted under the umbrella of W2010 will aid in the development of national and international genetic evaluation programs for improved feed efficiency.  This, in turn, will allow beef cattle breeders to use high efficiency cattle in their herds to reduce the feed cost of production and improve profitability.

Future Work: A divergent selection experiment was initiated in 1989 to investigate the influence of changes in serum IGF-I concentration on economically important traits in purebred Angus beef cattle. The selection experiment included 100 spring-calving (50 high line and 50 low line) cows located at the Eastern Agricultural Research Station, Belle Valley, OH.

Beginning with the 2009 breeding season, the selection criterion in the IGF-I selection lines was changed from serum IGF-I concentration to ME EPD as provided by the Red Angus Association of America.  Females in the high line are mated to high (undesirable) ME EPD bulls and cows and heifers in the low line are mated to low (desirable) ME EPD bulls.  The first calves produced in this project at the Ohio station were born in the spring 2010 calving season.  The selection experiment is ongoing.

Texas A&M University: 

The following studies were carried out at Texas A&M University to meet the objectives of the W2010 multistate project:

Objective 1:  To understand biological sources of variation in efficiency of feed utilization as quantified by traits such as RFI.

A study was conducted to examine the associations between RFI, and metabolomic profiles and feeding behavior to identify potential biomarkers for RFI in feedlot cattle. Performance, dry matter intake (DMI) and feeding behavior traits were measured for 70 d in Angus crossbred steers using a GrowSafe system. Steers were classified into low (n = 52), medium (n = 64), and high (n = 52) RFI groups based on ± 0.5 SD from the mean RFI of 0.00 (SD = 0.82). Low RFI steers consumed 17% less (P < 0.0001) DMI (9.05 vs 10.89 ± 0.14 kg/d) and had 18% lesser (P < 0.0001) F:G (5.05 vs 6.11 ± 0.10) than high RFI steers, but ADG was not different (1.78 ± 0.04). Steers with low RFI generated $95 per head more (P < 0.001) profit compared to high-RFI steers even though carcass value was not affected by RFI classification. Blood samples were collected from steers with lowest RFI (n = 25) and highest RFI (n = 24) on day 70 of the trial, and serum metabolite concentrations analyzed using ¹H-NMR spectroscopy. Partial least squares (PLS; MetaboAnalyst) were used to examine associations between RFI, and metabolites and feeding behavior traits. Of the 12 feeding behavior traits evaluated, 4 traits had variable of importance in projection score (VIP) that were > 1.0, which included head-down (HD) duration, bunk visit (BV) duration, non-feeding interval (NFI) duration, and head-down to meal duration ratio (HD:MD). The first 2 components of PLS accounted for 54% of between-animal variance in RFI. Steers with low RFI had longer (P < 0.001) NFI duration (less time at the bunk), 45% lower HD duration, 35% lower BV duration, and 32% lower HD:MD ratio than high RFI steers. Of the 44 metabolites detected by ¹H-NMR, 5 metabolites had VIP scores > 2, which included glycine, betaine, tyrosine, valine, and leucine. The first 2 components of PLS accounted for 34% of between-animal variance in RFI. Steers with low RFI had higher (P < 0.001) concentrations of glycine, and lower (P < 0.06) concentrations of betaine, tyrosine, valine, and leucine than high-RFI steers. These preliminary results reveal that metabolomic profiling and feeding behavior may provide opportunities to identify biomarkers that are predictive of RFI in beef cattle. Further research is warranted to examine the repeatability and robustness of these biomarkers for prediction of RFI phenotypes in beef cattle.

Findings: There is now considerable evidence that genetic variation exists in growing beef cattle for feed intake unaccounted for by differences in weight and growth rate, defined as residual feed intake (RFI), thereby providing opportunities to improve profitability of beef production systems through reductions in feed inputs, with minimal influences on growth or mature size. The expense of measuring feed intake has limited implementation of selection programs that target this trait. This project seeks to develop technologies to improve the genetic merit of beef cattle for feed efficiency in order to reduce production costs, mitigate environmental effects of beef production systems and improve the competitive position of beef producers. Residual feed intake is a trait that reflects inherent inter-animal variation in biologically relevant processes that are related to feed efficiency like nutrient digestibility. These studies seek to better understand the biological basis for genetic variation in RFI, and to determine if physiological biomarkers associated with RFI may be useful indicator traits for RFI.

Impacts: This project seeks to develop technologies to improve the genetic merit of beef cattle for feed efficiency in order to reduce production costs, mitigate environmental effects of beef production systems and improve the competitive position of beef producers. Results from these studies indicate that RFI is not phenotypically associated with SC or semen-quality traits. Further, these results suggest that between-animal variation in feeding activity is closely associated with phenotypic variation in RFI providing evidence that these behavioral traits may be useful indicator traits for RFI in beef cattle.

University of Illinois: 

Following studies were conducted at University of Illinois aimed at identifying the relationship of feed intake and feed efficiency across different diet types and biological time points. The results of these experiments will facilitate the identification and selection of females at a young age that will be more efficient cows.

Two experiments were conducted to evaluate the relationship between measures of feed efficiency in growing and mature animals, as well as across diet types. In Exp. 1, Post-weaning DMI, ADG, and backfat were evaluated on Angus and SimAngus heifers (n=623) over a 6-yr period. Heifers received similar forage-based diets, and individual DMI were recorded using the GrowSafe system. Residual feed intake (RFI), residual BW gain (RG), and residual intake and BW gain (RIG) were calculated. Heifers were classified into high, medium, or low RFI, RG, RIG, and DMI groups. The objective of this experiment was to determine the relationship between post-weaning feed efficiency and intake in heifers, and subsequent cow performance and reproduction as 2-yr-old cows. As heifer RFI improved, cow forage DMI was reduced (P < 0.01). The RFI classification did not affect (P ≥ 0.07) reproductive traits; calf birth or weaning BW; cow BW, milk production, backfat, or BCS. Heifer DMI was highly correlated (P < 0.05) to cow forage intake. Heifers classified as low DMI were least frequently (P < 0.01) kept as replacements and were youngest (P = 0.04) at first calving. Calves from cows, classified as high DMI heifers, had the greatest (P < 0.01) birth BW; yet, there were no differences (P=0.60) in weaning BW. Intake classification had no effect (P ≥ 0.07) on cow BCS, backfat, or milk production. Cows, classified as low DMI heifers, weighed the least (P = 0.02) and had reduced (P < 0.01) hip heights at 60- and 240-d postpartum. Cows, classified as low DMI heifers, had reduced (P ≤ 0.01) DMI compared to cows within the high heifer DMI group. These data indicate that females classified as more efficient have reduced cow DMI without compromising production traits. In Exp. 2, Charolais crossbred heifers and steers (n=628) were fed for two 70d periods and DMI, ADG, and 12th rib fat thickness were recorded. Steers were fed grain-based diets during the growing and finishing periods to determine the effects of test period and timing on DMI and feed efficiency. Heifers were fed forage during the growing period and grain during the finishing period to test the effect of diet type on DMI and measures of feed efficiency. For each 70d test period, individual DMI was recorded using the GrowSafe system. Residual feed intake was calculated for each test period. Total feeding period ADG (FP_ADG) was calculated for steers by regressing all weights taken from feedlot arrival to final BW, which was calculated by dividing HCW by a standard dressing percentage (63%). Dry matter intake and RFI were correlated (r=0.56; P<0.01, and 0.63; P<0.01, respectively) for the growing and finishing periods of grain-fed steers. Average daily gain was not repeatable (r=0.11; P=0.06) across both test periods for steers. However, growing and finishing ADG were correlated (r=0.58; P<0.01, and r=0.69; P<0.01, respectively) to FP_ADG. To assess the potential of shortening the intake test, DMI was analyzed in 7d increments for grain-fed steers during the growing period. Regardless of test length, from 7 to 70d, DMI was correlated (r≥0.87; P<0.01) to total DMI during the growing period. Heifer forage DMI was correlated (r=0.58; P<0.01) to grain DMI; and, heifer forage ADG was negatively correlated (r=-0.30; P<0.01) to grain ADG. Forage and grain RFI were moderately correlated (r=0.40; P<0.01) for heifers.

Short-term Outcomes: One outcome of this project is the training and professional development of a PhD student. The student has not only had the experience of collecting and analyzing data but has also had the opportunity to attend professional meetings and present the results at field days to producers.

Outputs: We have collected feed intake and performance data on >600 replacement heifers and subsequently collected intake and performance data on ~400 of these females as 2-yr-old cows and ~150 as 5-yr-old cows. We have also collected feed intake on different diet types during the growing and finishing period of over 600 feedlot cattle. Two manuscripts are currently in review.

Activities: We have conducted experiments to achieve better understanding of relationships of feed intake and efficiency across different diet types and different biological time points. We have presented data at field days and conferences:

 “Beef Cow Feed Efficiency” presented at the California Cattleman’s Association Annual Meeting, November 20, 2015 in Reno, NV

“Effects of timing and duration of test period and diet type on intake and feed efficiency in Charolais-sired cattle” presented at the Beef Improvement Federation Annual Meeting, June 15, 2016 in Manhattan, KS

University of Kentucky

At University of Kentucky research has been performed to understand biological sources of variation in efficiency of feed utilization as quantified by traits such as RFI. KY Station will contribute to the achievement of Objective 1 by extracting RNA from animal’s demonstrating the extreme range of residual feed intake (RFI) performance (outlier animals; contributed by other stations) and conducting targeted and genomic expression profiles of selected tissues to determine the effect of RFI phenotype on known and elucidated regulatory and canonical gene networks.

What was accomplished: Improvement of feeding regimens for production animals has been hindered by a lack of fundamental knowledge about how the capacity to regulate nutrient absorption across cell membranes (a process mediated by “membrane transporters”) affects the function of metabolizing enzymes. The experimental hypothesis tested was that the expression pattern of hepatic glutamate transporter activity would shift as growing steers developed from growing to finishing production stages, in order to support increased hepatic glutamine synthetase activity and glutathione content in liver, Longissimus dorsi, and 12th-13th rib adipose tissues. Steers phenotypes were developed were developed and characterized, tissues harvested and fractionated, and biochemical activities and metabolite contents analyzed. The impacts of the above novel accomplishments and findings include the increased fundamental understandings that (1) hepatic canalicular and sinusoidal plasma membrane glutamate transport capacities, (2) total hepatic glutamine synthesis activity, and (3) glutathione content of Longissimus dorsi, and 12th-13th rib adipose tissues differentially shift as steers develop from growing (lean) to finishing (finished) production stages. These findings identify potential metabolic targets during critical developmental phases of fattening cattle, and that are of interest/applicable to both the production animal and biomedical communities.

Conclusion: We developed protocols for, and identified changes in expression of, glutamate transporter and utilizing enzyme activities likely to be associated with putative changes in hepatic metabolism in high versus low RFI growing cattle.

Opportunities for Training and Professional Development: Graduate (3), and undergraduate (2) students, from the University of Kentucky and University of Guelph received training in (and conducted) the experimental design, statistical analyses, and bioinformatics analysis of targeted mRNA/protein and transcriptomic experiments.

Dissemination of Results: Publication in peer-reviewed manuscripts and presentation at producer field days.

Participants: Individuals: James Matthews (PI), Kwangwon Son (technician), Jing Huang (Ph.D. student), Qing Li (Ph.D. student), Yang Jia (Ph.D. student), Doreeyda Calcoa (B.S. student), Darcie Meimer (B.S. student).

Partner Organizations: Alltech Biotechnology, Inc.; Agricultural Research Service - Forage and Animal Production Research Unit, Lexington, KY.

Target Audiences: Cattleman associations; production- and biotechnology-based agriculture industries and academic representatives; biomedical and pharmaceutical community representatives.

Outputs: The identification of treatment-affected pathway genes and proteins have identified biomarkers for future studies, as well as adding knowledge to the fundamental physiology of these gene products.

Impacts: Feed constitutes a major input to beef production, and is, in fact, the largest single expense in most commercial beef production enterprises. Efficiency of feed utilization is, therefore, an obvious candidate for improvement in order to reduce cost of beef production. Studies conducted under the umbrella of W2010 will aid in the development of national and international genetic evaluation programs for improved feed efficiency. This, in turn, will allow beef cattle breeders to use high efficiency cattle in their herds to reduce the feed cost of production and improve profitability.

Plans for the Next Year:  We will continue our elaboration of bovine gene products (mRNA and protein) in pathways likely to be differentially-expressed in high versus low RFI beef animals. We will also continue elaboration of gene products (mRNA and protein) and protein activities responsible for (primarily) alpha-keto acid and nitrogen metabolism in liver and other bovine tissues to facilitate their characterization in high and low RFI beef animals, identified by other W2010 participants.

University of Tennessee

The University of Tennessee Institute of Agriculture continues its research to investigate gut microbiome influences on beef cattle feed efficiency, as well as the effect of feed additives on gas and methane production and methanogen abundances.

 Within the last year, the University of Tennessee Institute of Agriculture (UTIA) has made several strides to fulfill the objectives of the W2010 Multistate Research Project.  The W2010 has four major objectives focusing on feed efficiency in beef production systems. 

1. To understand biological sources of variation in efficiency of feed utilization.
2. To discover physiological biomarkers and genetic markers for RFI.
3. To develop EPDs, informed by molecular studies in building multi-trait selection indices and decision-support tools to facilitate selection for improved FE in beef cattle.
4. To develop producer educational programs to enhance technology adoption by the beef industry.

Both researchers at this station actively and exclusively participate in objective one.  Within 2016, much basic research has been conducted to initially examine the microbial populations and associated changes within the gut as a function of varying feed efficiency phenotypes.  Novel associations were identified between the jejunal bacterial communities and feed efficiency in steers.  Specifically, these association were identified within specific microbial taxa and operational taxonomic units (OTU). Methods to these studies were also reevaluated and published as method manuscripts in order to facilitate novel research.  As methane production contributes to overall energy efficiency, especially in grazing beef cows, studies funded in 2015 were initiated to examine methane mitigation strategies, focusing on biochar supplementation utilizing in vitro studies.

As publications are the primary tangible result expected from the project, our research findings were publicized to the academic community through peer-reviewed publications and conference presentations.  Some research findings were brought to classroom teaching. Graduate and undergraduate students were also involved in the research projects. The target audience includes producers, community, industry, commodity production groups, foundations, and other stakeholders involved in beef production.

Outputs: Three research publications, three invited research talks at national meetings, and one invited review have been developed from this station in 2016 as a result of the W2010 multistate project. 

Activities: We continue to work on research pertaining to adaptive mechanisms that promote energy efficiency in grazing beef cows and nutrition and host interactions with the ruminal and lower GIT microbial communities.  Specifically, we continue to progress with characterizing and understanding microbial influences in the rumen as a function of feed efficiency, methane production, and growth strategies.

A graduate textbook entitled, “Beef Biotechnology”, is being developed among members of this multistate project and edited by Drs. Phillip R. Myer and Ky G. Pohler at the University of Tennessee Institute Of Agriculture. This textbook is being developed to address updates in animal science, scientific methods, and production in American beef systems. Its delivery is expected in 2018.

Milestones: In order to develop a joint funding proposal including all participants who wish to contribute, as delineated in the project, two grant proposals were submitted to the USDA-NIFA Agriculture and Food Research Initiative Competitive Grants Program, Foundational Program, within the Animal Health and Production and Animal Products - Animal Nutrition, Growth and Lactation program area. These consisted of scientists from both the University of Tennessee Institute of Agriculture and USDA-ARS-USMARC.

Impact:

Microbial community profiles of the jejunum from steers differing in feed efficiency

Previously, associations between the bovine ruminal microbiome and feed efficiency have been reported, but few studies have examined the relationship between the microbial communities in distal portions of the GIT and feed efficiency. Within the jejunum, important functions include the enzymatic breakdown of nutrients and their absorption. This study was able to identify specific associations at the bacterial 16S-level with feed efficiency, ADG, and ADFI in the jejunum of steers. The majority of the taxa and OTU identified as associating with changes in feed efficiency in this study were related to the known fermentative and metabolic activities in the cattle jejunum, based on the putative microbial functions, and may also play a role in affecting downstream associations with the digesta and microbial communities in the distal GIT.

Evaluation of 16S rRNA amplicon sequencing using two next generation sequencing technologies for phylogenetic analysis of the rumen bacterial community in steers.

In this study, sequencing methods and technologies were scrutinized and examined to best determine the highly diverse steer rumen microbial communities and the impact of technology selection on resultant phylogenetic profiles.  The impact of this research allows insight and application to better conduct accurate community analyses for rumen microbiome studies.

Two grants were awarded from industry sources to address feed efficiency and nutrition within beef cattle, entitled:

• Effect of Biochar on Forage Digestibility, Methane Production, and Methanogens ($23,982) 12/07/15 – 8/31/2016
• Rumen protozoal community composition from growing steers differing in RFI ($228,617) 7/25/16 - 7/24/17

These projects will carry into 2017, with outputs and products delivered in the same year.

University of Nebraska

Research at University of Nebraska is continuing to investigate the Genotype X microbiota interactions in the feed efficiency phenotype. Additionally, they are also investigating the microbial community composition in high and low efficiency animals to identify phenotypic traits in the Microbiome that affects feed efficiency. They are collaborating with USMARC (US Meat Animal Research Center) on this effort. To this effect, We have phenotyped over 600 animals for rumen microbial community composition. Additionally, all animals have been genotyped using the 50K SNP assays to develop a subset of single nucleotide polymorphisms (SNP) that can be used for selection and for QTL detection.

Thus far, the GWAS analysis is underway. Additionally, we are focusing on identifying features of the microbiome that influences the feed efficiency phenotype. To this effect, we are using a sub set of data from USMARC looking at both steers and heifers.

Data used in this study were collected from a cohort of heifers (n = 146) during 2009 and a cohort of steers (n = 141) during 2014. Animals came from a population of cattle that has been developed to have high percentages of the following breeds: Angus, Beefmaster, Brahman, Brangus, Braunveih, Charolais, Chiangus, Gelbvieh, Hereford, Limousin, Maine Anjou, MARC II, MARC III, Red Angus, Red Angus × Simmental, Romosinuano, Salers, Santa Gertrudis, Shorthorn, and Simmental. Heifers were fed for 84 d a ration (dry matter basis) comprised of 70% corn silage and 30% alfalfa hay and steers were fed for 78 d a ration (dry matter basis) comprised of 57.6% dry-rolled corn, 30% wet distillers grains with solubles, 8% alfalfa hay, and 4.4% vitamin and mineral supplement. For each cohort, individual intake was measured using an Insentec feeding system (Marknesse, The Netherlands) and total body weight gain (BWG) was measured at the end of the feeding period for three consecutive d. In addition, a rumen sample was collected for all animals via esophageal tubing on the last day of the feeding period.

Average daily dry matter intake (DMI) and BWG were calculated for each animal within cohort. Then, a linear model with breed fractions as covariates was fitted for both DMI and BWG and residuals were extracted. This was done to account for the inherent differences in DMI and BWG across breeds (Schenkel et al., 2011). Residuals of average daily BWG were regressed on residuals of average daily DMI for both steers and heifers. Based on the regressed data, four animals from each Cartesian quadrant (n=16/cohort) were sampled. This approach generated a 2 × 2 factorial design with DMI and BWG at two levels (high and low) (Fig 1).

Data processing and bacterial community analysis: Assembly of contigs and subsequent quality filtering that included removal of sequences with ambiguous bases, incorrect length, or improper assemble were done using MOTHUR v.1.36.1 (Schloss et al., 2009). Quality filtered sequences were then clustered into OTUs using the UPARSE pipeline (USEARCH v7.0.1090) (Edgar, 2013). Clustering steps included dereplication, sorting by size (descending and not retaining singletons), filtering of chimeras using UCHIME (Edgar et al., 2011) with ChimeraSlayer gold.fa as the reference database, and mapping sequences to operational taxonomic units (OTUs) at a 97% identity threshold. Representative OTU sequences were assigned taxonomy using QIIME v.1.9.1 (Caporaso et al., 2010) with the MOTHUR method, which uses a naive bayes classifier similar to the RDP Classifier (Wang et al., 2007), and with the Greengenes database (McDonald et al., 2012) as reference sequences. Representative OTU sequences were aligned against the SILVA reference alignment database v123. OTU sequences that did not align correctly were removed to ensure all sequences overlapped the V4 region.

Statistics: The OTU table was rarefied across samples to the lowest sample depth to 9,010 reads for the heifer cohort and 12455 for the steer cohort using QIIME based on the Mersenne Twister pseudorandom number generator. All statistical analyses were performed at an even depth across samples. Alpha metrics Chao1 and Shannon index were used to evaluate species richness and diversity across feed efficiency groups within cohort. Core bacterial community composition differences were evaluated using the weighted UniFrac distance matrix as an input for a permutational multivariate analysis of variance (PERMANOVA). The weighted UniFrac distance matrix was also used in the principal coordinate analysis (PCoA) to assess clustering between samples. To identify specific OTUs differences across feed efficiency phenotypes, the linear discriminant analysis effect size (LEfSe) was used.

Results and Outputs: Species richness (Chao1; t-test, P ≥ 0.72) and diversity (Shannon; t-test, P ≥ 0.46) did not differ across feed efficiency groups for both cohorts. Rarefaction curves displayed adequate sampling depth for both heifers and steers. In addition, bacterial communities of heifers and steers were characterized at 94% and 98%; respectively, based on Good’s coverage estimator. Overall, efficiency groups did not influence alpha diversity metrics.  For both heifers (PERMANOVA, P = 0.63) and steers (PERMANOVA, P = 0.12), samples did not clustered based on feed efficiency group in the PCoA plot. This meant that overall bacterial community composition was similar regardless of feed efficiency phenotype. However, at the OTU level, 65 OTUs across feed efficiency groups for heifers and 14 OTUs across feed efficiency groups for steers were found to differ (P < 0.05). Main differential OTUs belonged to the Prevotellaceae and Ruminococcaceae families for heifers and the Lachnospiraceae and Prevotellaceae families for steers.

Future work: Associations will be assessed between differential OTUs and feed efficiency phenotypes. Then a model will be built to predict feed efficiency phenotype from microbial features.

Impact: Determining the underlying mechanisms of individual differences in the efficiency of feed utilization and improving our understanding of effects of selection for efficiency, management suggestions for producers, potential targets for improving efficiency, and ability to identify a biomarker.

Biological factors affecting feed efficiency in cattle are not fully understood and may include nutritional implications such as nutrient digestibility and utilization by the animal.

This project seeks to develop technologies to improve the genetic merit of beef cattle for feed efficiency in order to reduce production costs, mitigate environmental effects of beef production systems, and improve the competitive position of beef producers. Results from these studies indicate that RFI is not phenotypically associated with scrotal circumference or semen-quality traits. Further, these results suggest that between-animal variation in feeding activity is closely associated with phenotypic variation in RFI, providing evidence that these behavioral traits may be useful indicator traits for RFI in beef cattle.

Identification of biomarkers for maintenance energy requirements will allow identification and selection of more efficient animals and therefore improve efficiency of production.

Feed constitutes a major input to beef production, and is, in fact, the largest single expense in most commercial beef production enterprises.  Efficiency of feed utilization is, therefore, an obvious candidate for improvement in order to reduce cost of beef production.  Studies conducted under the umbrella of W2010 will aid in the development of methods to manipulate the rumen microbial community to increase performance and to identify genetic factors that help structure microbial communities. This, in turn, will allow beef cattle breeders to use high efficiency cattle in their herds to reduce the feed cost of production and improve profitability.

Publications

University of Califonia-Davis

Dykier, K. C., and R. D. Sainz. 2016. Performance and net energy in high and low RFI beef cattle. J. Anim. Sci 94 (E-Suppl. 5): 7.

Dykier, K. C., and R. D. Sainz. 2016. Performance and net energy in High and Low RFI beef cattle on restricted intake. J. Anim. Sci 94 (E-Suppl. 5): 115.

Werth, S. J., J. W. Oltjen, E. Kebreab, and F. M. Mitloehner. 2016. A life cycle assessment of a beef feedlot finishing ration supply chain in California. J. Anim. Sci 94 (E-Suppl. 5): 568.

Iowa State

Russell, J. R., and S. L. Hansen. 2015. Influence of Feed Efficiency Ranking on Diet Digestibility and Performance of Beef Steers. Iowa State University Animal Industry Report:2960.

Russell, J., E. Lundy, S. L. Hansen.  2016. Growth and Carcass Characteristics of Feed Efficiency Classified Cattle Fed Corn or Roughage-Based Diets and Finished with Corn or Byproduct-Based Diets. Iowa State University Animal Industry Report.

Russell, J. R., E. L. Lundy, N. O. Minton, W. J. Sexten, M. Kerley and S. L. Hansen. 2016. Influence of growing phase feed efficiency classification on finishing phase growth performance and carcass characteristics of beef steers fed different diet types. J. Anim. Sci. 94 (Suppl. 3) (Abstr.) 2nd place PhD poster competition.

Russell, J. R., W. J. Sexten, M. S. Kerley, and S. L. Hansen. 2015. Relationship between antioxidant capacity, oxidative stress and feed efficiency in beef steers. J. Anim. Sci. 93 (Suppl. 3):334. (Abstr.)

Russell, J. R., N. O. Minton, W. Sexten, M. Kerley, S. L. Hansen. 2016. Influence of feed efficiency classification on diet digestibility and growth performance of beef steers. J. Anim. Sci. First look. doi: 10.2527/jas.2015-9949.

Russell, J. R., E. L. Lundy, N. O. Minton, W. J. Sexten, M. S. Kerley, S. L. Hansen, and National Program for Genetic Improvement of Feed Efficiency in Beef Cattle. 2016. Influence of growing phase feed efficiency classification on finishing phase growth performance and carcass characteristics of beef steers fed different diet types. J. Anim. Sci. 94:1610–1619.  doi: 10.2527/jas.2015-0267

Russell, J. R., N. O. Minton, W. J. Sexten, M. S. Kerley, S. L. Hansen, and National Program for Genetic Improvement of Feed Efficiency in Beef Cattle. 2016. Influence of feed efficiency classification on diet digestibility and growth performance of beef steers. J. Anim. Sci. (in press). doi:10.2527/jas.2015-9949.

Russell, J. R., W. J. Sexten, M. S. Kerley, and S. L. Hansen. 2016. Relationship between antioxidant capacity, oxidative stress, and feed efficiency in beef steers. J. Anim. Sci. (in press) doi:10.2527/jas.2016-0271.

Russell, J. R. 2015. Feed efficiency in beef cattle: relationship with digestibility, antioxidant activity, oxidative stress, growth performance and carcass characteristics. Ph.D. Diss. Iowa State Univ., Ames. 

Russell, J. R. 2015. Update on the feed efficiency project. Iowa State University Beef Nutrition Research Showcase. October. Ames, IA.

Hansen, S. L. and D. L. Loy. 2015. Update on the feed efficiency project. NCCC-308 Regional Feedlot Committee Report. May. Scottsbluff, NE.

Montana State University

Lean, Ian, M. Lucy, J. McNamara, B. Bradford, E. Block, J. Thomson, J. Morton, P. Celi, A. Rabiee, J. Santos, W. Thatcher, S. LeBlanch. 2016. Invited Review: Recommendations for reporting intervention studies on reproductive performance in dairy cattle: Improving design, analysis, and interpretation of research on reproduction. Journal of Dairy Science. 99:1-17

Thomson, J. M. 2016. Impacts of Environment on Gene Expression and Epigenetic Modification in Grazing Animals. J Anim Sci. Accepted for publication

M.D. Miller, G. E. Carstens, J. M. Thomson, J. G. Berardinelli, M.R. Herrygers, J. White, L. O. Tedeschi, P. K. Riggs. 2016. Associations between RFI, and metabolite profiles and feeding behavior traits in feedlot cattle. J. Anim Sci. 94 (E-suppl 5):1491

M.R. Herrygers, J. M. Thomson, K. A. Perz, K. B. Herrygers, K. Metcalf, M. Knerr, P. Merta, J. G. Berardinelli. 2016. Long-term progesterone influence on feed efficiency, body composition, non-esterified fatty acids and metabolic hormones in mature Rambouillet ewes. Proc. West. Sec. Am Soc. Anim. Sci. Vol. 68

2016. A. Perz. J. G. Berardinelli, R. A. Shevitshi, J. W. White, J. M. Thomson. 2016. Use of a human tri-axial pedometer for measurement of sheep activity. Proc. West. Sec. Am Soc. Anim. Sci. Vol. 68
2017. F. Williams, J. A. Boles, M. R. Herrygers, J. G. Berardinelli, M. C. Meyers, J. M. Thomson. 2016. Relationship between current temperament measures and physiological responses to handling of feedlot cattle. Proc. West. Sec. Am Soc. Anim. Sci. Vol. 68
2018. A. Perz, J. G. Berardinelli, L. N. Park, R. K. Pollard, C. M. Page, W. C. Stewart, J. M Thomson. 2016. Repeatability of residual feed intake and indices of body composition in growing Columbia ewes fed the same diet. J. Anim Sci. 94 (E-suppl 5):777

Ohio State University

Davis, M. E., P. A. Lancaster, J. J. Rutledge, and L. V. Cundiff.  2016.  Life cycle efficiency of beef production:  VIII. Relationship between residual feed intake of heifers and subsequent cow efficiency ratios.  J. Anim. Sci. (in review).

Texas A&M University

Carstens, G.E. How between-animal variation in feed efficiency and carcass-quality traits impacts profit of feedlot steers. Proc. of XVIII Symposium on Feedlot Cattle. Monterrey, Mexico. Pp. 20-25.

University of Illinois

Cassady, C., T. L. Felix, D. W. Shike. 2016. Effects of diet type and feeding phase on intake and feed efficiency of beef cattle. Midwest Section of Animal Sciences Meeting. Des Moines, IA. J. Anim. Sci. 94 (E-Suppl. 2): 379

Shike, D.W., C. J. Cassady, T. L. Felix, and J. E. Beever. 2016. Effects of timing and duration of test period and diet type on intake and feed efficiency in Charolais-sired cattle. Proc. 2016 Beef Improvement Federation: Research Symposium & Annual Meeting. Manhattan, KS p. 57-64.

University of Kentucky

Liao, S. F., J. A. Boling, and J. C. Matthews. 2015. Gene Expression Profiling Indicates an Increased Capacity for Proline, Serine, and ATP Synthesis and Mitochondrial Mass, by the Liver of Steers Grazing High vs. Low Endophyte-infected Tall Fescue. Journal of Animal Science 93:5659-5671. doi:10.2527/jas2015-9193.

University of Tennessee

Myer, P.R., Wells, J.E., Smith, T.P.L., Kuehn, L.A. and Freetly, H.C., 2016. Microbial community profiles of the jejunum from steers differing in feed efficiency. Journal of Animal Science, 94(1), pp.327-338. doi:10.2527/jas2015-9839.

Myer, P., M. Kim, H. C. Freetly, and T. P. L. Smith.  2016.  Evaluation of 16S rRNA amplicon sequencing using two next generation sequencing technologies for phylogenetic analysis of the rumen bacterial community in steers. Journal of Microbiological Methods, 127:132–140. doi:10.1016/j.mimet.2016.06.004

Myer, P., M. Kim, H. C. Freetly, and T. P. L. Smith.  2016.  Metagenomic and near full-length 16S rRNA sequence data in support of the phylogenetic analysis of the rumen bacterial community in steers.  Data in Brief, 8:1048-1053. doi:10.1016/j.dib.2016.07.027

Mulliniks, J.T., Rius, A.G., Edwards, M.A., Edwards, S.R., Hobbs, J.D. and Nave, R.L.G., 2015. FORAGES AND PASTURES SYMPOSIUM: Improving efficiency of production in pasture-and range-based beef and dairy systems. Journal of Animal Science, 93(6):2609-2615. doi:10.2527/jas.2014-8595

Abstracts from scientific or discipline meetings; papers from conference proceedings

Myer, P., M. Kim, H. C. Freetly, and T. P. L. Smith.  2016.  Evaluation of 16S rRNA Amplicon Sequencing Using Two Next-Generation Sequencing Technologies for Phylogenetic Analysis of the Rumen Bacterial Community in Steers.  Microbe 2016; American Society for Microbiology General Meeting, Boston, MA.

2016. C. Freetly, and P. Myer. 2016. Feed efficiency and the microbiota of the alimentary tract.  Proceedings of the Beef Improvement Federation Annual Meeting and Symposium, June 14-17, 2016, Manhattan, KS. p. 65-74.  (invited)

Myer, P., J. E. Wells, T. P. L. Smith, L. A. Kuehn, and H. C. Freetly.  2016.  Gut bacterial communities and their association with production parameters in beef cattle.  Journal of Animal Science, 94(Supplement 2)183-184.  (invited)

Myer, P., J. E. Wells, T. P. L. Smith, L. A. Kuehn, and H. C. Freetly.  2016.  Analysis of the gut microbiome in beef cattle and its association with feed intake, growth, and efficiency.  Journal of Animal Science, 94 (E-Supplement 5) 211-212.  (invited)

University of Nebraska

Paz, HA, Anderson, CL, Muller, MJ, Kononoff, PJ, and Fernando SC. 2016. Rumen Bacterial Community Composition in Holstein and Jersey Cows Is Different under Same Dietary Condition and Is Not Affected by Sampling Method. Frontiers in Microbiology http://dx.doi.org/10.3389/fmicb.2016.01206

Christopher L. Anderson, Galen E. Erickson, Jim C. MacDonald, and Samodha C. Fernando. 2016. Rumen bacterial communities can be adapted faster to high concentrate diets than currently implemented feedlot programs. Journal of Applied Microbiology. 120 (3): 588-599 doi: 10.1111/jam.13039

Ramirez-Ramirez, Hugo; Harvatine, Kevin; Castillo Lopez, E; Fernando, SC; Aluthge, N; Jenkins, Chad; Anderson, Christopher; Kononoff, Paul.. 2015. Reduced fat dried distillers grains with solubles reduces the risk for milk fat depression and supports milk production and ruminal fermentation in dairy cows. Journal of Dairy Science. 99 (3): 1912-1928

Abstracts

Sanjay Antony-Babu, Jennifer Clarke and Samodha C. Fernando. 2016. Metagenomics reveals larger role of syntrophic eubacteria in rumen methane production. International Society of Microbial Ecology, Montreal, Canada. August 21st to 26th

Tom, W.T., Judy, J.J., Kononoff, P.J., Fernando, S. C. (2016, July). 16S rRNA Bacterial sequences suggest dietary intervention can be used to change microbial community structure to reduce methane emission in Holstein dairy cattle. Joint Annual Meeting of the American Society of Animal Science (ASAS), The American Dairy Science Association (ADSA), the Western Section of the American Society of Animal Science (WSASAS), and the Canadian Society of Animal Science (CSAS), Salt Lake City, UT

Judy, J.J., Brown-Brandi, T., Fernando, S. C., Kononoff, P.J. (2016, July). Manipulation of lactating dairy cows diets using reduced-fat distillers grains, corn oil and calcium sulfate to reduce methane production measured by indirect calorimetry. Joint Annual Meeting of the American Society of Animal Science (ASAS), The American Dairy Science Association (ADSA), the Western Section of the American Society of Animal Science (WSASAS), and the Canadian Society of Animal Science (CSAS), Salt Lake City, UT

Alterations of the rumen bacterial and archaeal communites in growing and Finishing beef cattle and its effects on methane emissions. Allison L. Knoell1, Christopher L. Anderson, Anna Pesta, Galen Erickson, Terry Klopfenstein, Samodha C. Fernando (2016). Midwest Animal Science Meeting Des Moines, IA (March 12-16

Effect of protein supplementation of low-quality forage diets on enteric methane production of beef steers. A.L. Shreck, N. D. Aluthge, J.S. Jennings, S.C. Fernando, and N.A. Cole (2015). Joint Annual Science Meeting held by the American Dairy Science Association, American Society of Animal Science and Canadian Society of Animal Science, Orlando, FL (July 12-16)

Greenhouse gas emissions and nitrogen cycling from beef production systems: Effects of climate, season, production system, and diet. Galen E. Erickson, Samodha C. Fernando, Terry J. Klopfenstein, Andrea K. Watson, James C. MacDonald, Anna C. Pesta, Allison L. Knoell, and Henry Paz (2015). Joint Annual Science Meeting held by the American Dairy Science Association, American Society of Animal Science and Canadian Society of Animal Science, Orlando, FL (July 12-16)