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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Research Project #423791

Research Project: Alleviating Rate Limiting Factors that Compromise Beef Production Efficiency

Location: Livestock and Range Research Laboratory

2014 Annual Report

1: Determine the impact of the level of harvested feed input on the sustainability of beef production systems, including annual reproductive success, lifetime productivity, and progeny performance. 2: Evaluate use of dormant, animal-harvested forages as a substitute for mechanically harvested feeds in developing replacement heifers. 3: Develop new and better genetic and physiological indicators of fertility in yearling bulls and beef cows to enhance annual and life-cycle reproductive success. 4: Assess locus-specific genetic effects attributable to heterozygosity on reproductive success and productivity in production systems making differential use of native range forages. 5. Improve breeding and management decisions by characterizing current genetic and phenotypic variation within and between predominant beef breeds and crosses using novel genomic and genetic evaluation technologies and identify novel genomic variants to optimize forage based production efficiencies for beef cattle within and across diverse physical environments in the US Great Plains.

Feed consumption and replacement of cows, culled for reproductive failure, are two primary determinants of beef production efficiency. Our overarching goal is to develop strategies and technologies to alleviate these limitations. Sufficient nutrient intake resulting in adequate body energy stores are believed essential for reproduction. Thus, producers are challenged to match nutritional environment, which is subject to seasonal and annual variation, and various genotypes to obtain sustainable reproduction and retention rates. Our approach is, of necessity, long-term and multi-disciplinary, involving both basic and applied aspects of genetics, nutrition, and physiology in a semi-arid grazing production system. This proposal brings to fruition ongoing research and establishes investigations of genetic by environmental interactions and physiological mechanisms limiting reproductive success. Four distinct cattle populations (an intercross of Charolais (25%), Red Angus (50%) and Tarentaise (25%), Line 1 Hereford, purebred Angus, and Hereford-Angus herd) will be used to facilitate assessment of genetic factors affecting fitness (hybrid vigor). Distinct nutritional environments that utilize different contributions of harvested and grazed forage will be imposed to challenge the nutrition-reproduction interface to elucidate genetic, physiological, and management factors influencing feed utilization and lifetime productivity. Identification of genetic, nutritional, and physiological mechanisms that limit or contribute to beef production efficiency will facilitate early in life selection and management of replacement animals most fit for particular production environments. This research will result in the establishment of heifer development protocols that provide producers options for dealing with annual variations in availability and quality of forage.

Progress Report
Phenotypic and genotypic data continue to be collected to assess the impact of the level of harvested feed input on the sustainability of beef production systems, including annual reproductive success, lifetime productivity, and progeny performance. Data have been analyzed to determine the effects that level of harvested feed provided to the individual animal and its dam have on herd retention. Heifer calves born in 2013 were subjected to experimental treatments (fence line weaned and pasture developed vs. feedlot weaning and development). Methodology was established to measure supplemental feed intake, heart rate and activity in individual animals in pasture setting. Oocytes were collected, in the form of cumulus oocyte complexes, from cows using ultrasound-guided follicle aspiration, denuded of cumulus cells, and snap frozen for assessment of transcriptional differences in physiological maturity. Assessment of the follicular fluid metabolome and steroid concentration from these follicles has been initiated as phenotypic indicators of fertility. Purchased and reared Angus females have been added to the herd for the heterosis project. Data on feed intake, postweaning development traits and fertility were collected.

1. Ovarian and uterine contributions to reproductive failure in cattle. Reproductive success is dependent on sequential success of distinct physiological events transpiring at different organs throughout the body. Basic knowledge of where failure occurs in the sequence of events is extremely limited. Research by ARS scientists at Miles City, MT, characterized the impact of ovulatory follicle size and differential gene expression in the bovine endometrium on reproductive loss in cattle. Results from this research provides the foundation for thorough understanding of contributing factors of reproductive failure in cattle.

2. Estimates of beef cattle energy and protein nutritional needs published in the 7th edition of the National Research Council Beef Cattle Requirements (NRC) may not be correct when applied to grazing beef females in extensive arid environments. Assessments of beef cow and heifer energy and protein balance and efficiency in extensive grazing settings have occurred on a nominal basis over short time intervals. Because of this, data used to inform nutrient requirement models representing yearly or lifetime nutrient utilization are imprecise. Research by ARS scientists at Miles City, MT, indicated that cattle adapted to extensive rangeland environments maintain productivity at dietary levels of energy and protein that fall below the model derived values published in NRC. These results provide evidence that efficiency of nutrient utilization may be enhanced when cattle are maintained in extensive rangeland conditions. Producers using requirements to assess nutrient needs in arid environments may improve economic efficiency by using values at least 5% less than NRC suggests.

3. Development of methodology to estimate energy utilization by grazing livestock. Methodology to identify differences in animal efficiency under range/pasture conditions are lacking, and thus most research on efficiency is conducted in confinement settings. Research by ARS scientists at Miles City, MT, have established a procedure to acquire estimates of energy expenditure on individual animals fitted with portable heart rate monitors and GPS devices under range conditions. This methodology is expected to facilitate research focused on improving production efficiency in cattle.

Review Publications
Abreu, F.M., Cruppe, L.H., Maquivar, M., Utt, M.D., Madsen, C.A., Vasconcelos, J.M., Mussard, M.L., Day, M.L., Geary, T.W. 2014. The effect of follicle age on conception rate in beef heifers. Journal of Animal Science. 92:1022-1028.
Abreu, F.M., Geary, T.W., Cruppe, L.H., Madsen, C.A., Jinks, E.M., Pohler, K.G., Vasconcelos, L.M., Day, M.L. 2014. The effect of follicle age on pregnancy rate in beef cows. Journal of Animal Science. 92:1015-1021.
Whitehurst, W.A., Paterson, J.A., Harbac, M.M., Petersen, M.K., Duff, G.C., Geary, T.W., Zanton, G.I., Wistuba, T.J. 2014. Comparison of methionine hydroxy analogue chelated versus sulfate forms of copper, zinc, and manganese on growth performance and pregnancy rates in yearling beef replacement heifers. Professional Animal Scientist. 30:62-67.
Matjuda, L.E., MacNeil, M.D., Maiwashe, A., Leesburg, V.L., Malatje, M. 2014. Index-in-retrospect and breeding objectives characterizing genetic improvement programs for South African Nguni cattle. South African Journal of Science. 44:161-172.
Leesburg, V.L., MacNeil, M.D., Neser, F.C. 2014. Influence of Miles City Line 1 on the United States Hereford Population. Journal of Animal Science. 92:2387-2394.
Minten, M.A., Bilby, T.R., Bruno, R.S., Allen, C.C., Madsen, C.A., Wang, Z., Sawyer, J.E., Tibary, A., Neibergs, H.L., Geary, T.W., Bauersachs, S., Spencer, T.E. 2013. Effects of fertility on gene expression and function of the bovine endometrium. PLoS One. 8(8):1-14 (e69444).
Pohler, K.G., Geary, T.W., Johnson, C.L., Atkins, J.A., Jinks, E.M., Busch, D.C., Green, J.A., Macneil, M.D., Smith, M.F. 2013. Circulating bovine pregnancy associated glycoproteins (bPAGs) are associated with late embryonic/fetal survival but not ovulatory follicle size in suckled beef cows. Journal of Animal Science. 91:4158-4167.