Location:2008 Annual Report
1a. Objectives (from AD-416)
Objective 1: Develop methods and strategies for measuring feed intake and related phenotypes of steers, replacement heifers, and mature cows. Objective 2: Determine breed and within-breed genetic effects on feed efficiency, growth, and fertility of cattle. Sub-objective 2.A. Determine breed and within-breed genetic effects on nutrient utilization. Sub-objective 2.B. Determine breed and within-breed genetic effects on reproductive efficiency. Objective 3: Discover QTL and estimate genomic effects for traits contributing to differences in efficiency among cattle. Objective 4: Fine map identified QTL for reproductive rate in cattle. Objective 5: Enhance existing simulation models to investigate genetic-by-environmental interactions on beef life-cycle efficiency and integrate into decision support software. Objective 6: Identify nutritional effects on expression of genes and subsequent phenotypes, and integrate this information with our current understanding of physiology to enhance management decisions.
1b. Approach (from AD-416)
Major challenges of the beef cattle industry are to improve efficiency and reduce negative environmental impacts of animal production. Provision of nutrients (feed) constitutes about 65 to 75% of the cost of beef cattle production. Less than 20% of the nutrients consumed are converted to useful products. The incomplete and inefficient utilization of nutrients has an adverse effect on efficiency of production and a negative effect on the environment. Traditional approaches have resulted in successful alteration of production traits such as weight at slaughter, growth rate, mature weight, and body composition, but have not altered feed efficiency. Those approaches do not provide the ability to economically identify animals with high genetic merit for feed efficiency on a timely basis, because the required phenotypic data are impractical to obtain in normal genetic evaluation programs. Available evidence suggests feed consumption and related traits are likely to be moderately heritable. These traits are extremely important components in any strategy for the permanent, cumulative, and sustainable genetic improvement of biological and economic efficiencies of beef production. Application of quantitative trait loci (QTL) technology provides opportunities to improve feed efficiency in beef production. The identification of QTL would make it possible to utilize the relatively large amount of observed variation and moderate heritability in improving feed efficiency. However, currently there are no tools (EPD, QTL, or markers for QTL) that facilitate direct selection to modify feed consumption, feed efficiency, or nutrient requirements in the growing-finishing animal or productive female. Research in this project is being undertaken to study genetic and environmental factors that lead to variation in efficiency in beef production. This project addresses measures of efficiency at different phases of the production system to identify those factors that have additive merit and antagonistic relationships across the different phases of production. The initial component of the project is to develop facilities and methodologies to efficiently collect economically and biologically important phenotypic data relevant to efficiency. After developing capabilities to measure the phenotypes, the contribution of genetics and environment/management to variation in efficiency of production will be determined. Genetic variation will be evaluated using both quantitative genetics and QTL discovery. Information gained from both the genetic and environmental studies will be used to parameterize simulation models that provide decision support software to allow producers to simulate potential outcomes to optimize production efficiency when different combinations of animal genetics and management strategies are used.
3. Progress Report
The research conducted address the following components of Food Animal Production National Program (NP 101) Action Plan; Component 1) Understanding, improving, and effectively using animal genetic and genomic resources and addresses Problem Statements 1A (Developing genome–enabling tools and reagents), and Problem Statement 1B (Identify functional genes and their interactions), and Component 2) Enhancing animal adaptation, well-being and efficiency in diverse production systems and addresses Problem Statement 2B (Reducing reproductive losses) and Problem Statement 2C (Improving efficiency of nutrient utilization and conversion to animal products). Approximately 1,250 steers, 750 heifers, and 250 cows have been phenotyped for feed efficiency. Genotyping using the Bovine50SNP beadchip generating greater than 50,000 DNA markers per animal has been completed on these same animals. A new facility to phenotype cattle for feed intake and feed behavior has been finished and is currently in use. The facility has a capacity of approximately 300 cattle. Over 22,000 feed and water events per day are generated by beef cattle using the facility. Feed intake data has been used to develop statistical models to partition variation into genetic and non-genetic components to estimate heritabilities and genetic correlations among measures of growth, carcass composition, temperament, and defined feed efficiency phenotypes. Simulation models have been written to predict the advantage in feedlot performance and cow/calf production when superior sires for feed efficiency are selected. Over 400 heifers and 400 cows that have DNA marker information have been phenotyped by ultrasonography for ovarian antral follicle number as a measure of fertility and stayability. Ovarian weights and follicle counts have been measured on 320 heifers and cows and correlated with age. Ovarian cortex was collected from 100 cows of different ages and antral follicle numbers to examine the expression of genes associated with oocyte quantity and quality. Oocytes from 75 cows have been sampled to determine the role of microRNAs in controlling expression of genes needed for early embryonic development. Hedgehog mRNA increases during follicular growth suggesting it may interact with the IGF system in follicle maturation and selection. IGF type 2 receptor sequesters IGF-II and attenuates its stimulatory effect on ovarian follicular development. Milk production has been measured in more than 400 heifers that have DNA marker information available. Udder structure and feet and leg soundness has been evaluated in over 500 cows that have DNA marker information. Using a low density single nucleotide polymorphism (SNP) map, a diagnostic DNA marker has confirmed a QTL for twinning and ovulation rate on bovine chromosome 5. Over 252 young heifers received nutrition treatments to evaluate the effect of nutrition during development on life-time productivity and well-being. Nutritional treatments have been applied to 400 cows to evaluate the effect of fetal nutrition on life-time productivity and well-being of their daughters.
1. Efficiency of energy retention in pregnant beef cows allows for the development of strategies that alter the time interval of the production cycle during which supplemental feed is offered. Providing supplemental feed to pregnant cows when grazed forages are not available is costly. Research conducted at the U.S. Meat Animal Research Center found that the efficiency of energy gain during late pregnancy was high which would allow for the development of management strategies that increase the use of grazed forages and/or alter the time that supplemental feed is fed. These results demonstrate how energy stored in the body of the cow can be used as part of a total feed management plan. This research addresses National Program Action Plan Component 2 “Enhancing animal adaptation, well-being, and efficiency in diverse production systems” and addresses National Program Action Plan Problem Statement 2C “Conversion to animal products.”
2. Calves born to cows bred increases in cows selected for increased ovulation rate, but increases above twin births may be reduced due to increased embryo and fetal mortality resulting from crowding in the uterus. The limitation of one calf per year limits the production potential of beef cattle. Research conducted at the U.S. Meat Animal Research Center found that selecting for increased ovulation rate can be used to increase the number of calves within a pregnancy thus increasing the annual production potential of a cow. However, capacity of the uterus to successfully support the growth of more than two calves may be limiting suggesting the need to include uterine capacity in a selection index for increased birth rate. These findings demonstrate that selection for increased birth rate in beef cattle can be used as a tool for developing cattle with higher production potential. This research addresses National Program Action Plan Component 2 “Enhancing animal adaptation, well-being, and efficiency in diverse production systems” and addresses National Program Action Plan Problem Statement 2B “Reducing reproductive losses.”
3. Amino acid availability increases when moderate quality forage is supplemented with dried distiller’s grains with solubles. Forage protein quality varies with locale and season and at times is not adequate to support the desired production level of grazing ruminants. Research conducted at the U.S. Meat Animal Research Center found that supplementation of grass hay with distiller’s grains compared to corn increased amino acid absorption. These findings suggest that dried distiller’s grains are a potential feed resource for supplementing low protein forages. This research addresses National Program Action Plan Component 2 “Enhancing animal adaptation, well-being, and efficiency in diverse production systems” and addresses National Program Action Plan Problem Statement 2C “Conversion to animal products.”
5. Significant Activities that Support Special Target Populations
Archibeque, S.L., Freetly, H.C., Ferrell, C.L. 2008. Feeding distillers grains supplements to improve amino acid nutriture of lambs consuming moderate-quality forages. Journal of Animal Science. 86(3):691-701.