Recipient Organization
SOUTH DAKOTA STATE UNIVERSITY
PO BOX 2275A
BROOKINGS,SD 57007
Performing Department
Animal & Range Sciences
Non Technical Summary
Fourteen million feeder cattle are finished annually in the U.S. and the National Beef Quality Audit listed among the greatest concerns with regard to beef carcass quality, inadequate marbling and excess external fat. An unfavorable distribution of carcass fat costs the beef industry an estimated $169 million annually, and this cost does not account for losses incurred as a result of poor feed efficiency that occurs with excessively fat cattle. Despite efforts to improve fat distribution in the beef carcass, external fat cover has worsened since 1995, and the percentage of carcasses grading USDA Choice or Prime has decreased from 84% to 60% since 1975. Most research aimed at improving carcass quality in beef cattle has focused on nutrition and management of the calf from birth through harvest. Less research has focused on the impact that maternal nutrition and uterine environment during development may have on mechanism that influence composition of gain in offspring. Additionally, interactions of plane of nutrition and specific genotypes on body composition have not been explored. This research will focus on the influence of maternal nutrition and interactions of nutrition and genotype on hormones and growth factors that influence composition of gain in beef cattle. Research projects will include: 1) manipulation dam nutrition during gestation and evaluating growth and carcass composition of the offspring, and 2) sorting cattle on the basis of genotype and evaluating differences in growth, carcass composition, and hormones and abundance of their receptors in target tissues. The intended outcome of this research is that ideal nutritional management strategies, relative to the genetic profile or stage of gestation in cattle can be developed and result in improved feed conversion efficiency and profitability for cattle producers.
Animal Health Component
80%
Research Effort Categories
Basic
10%
Applied
80%
Developmental
10%
Goals / Objectives
1) Investigate relationship of ghrelin and leptin, abundance of their receptors in target tissues, and the growth and transcription factors they influence on feed conversion efficiency and composition of gain; and 2) Investigate the interaction of nutrition and various genotypes on composition of gain and feed conversion efficiency. Specifically, sort cattle on the basis of single nucleotide polymorphisms (SNPs) for ghrelin, leptin, or other genes believed to influence composition of gain or feed conversion efficiency and study the physiological differences among these populations.
Project Methods
Maternal nutrition experiments will include treating gestating dams to ADEQUATE, RESTRICTED, or ABUNDANT nutrient supply. Beef NRC (2000) equations will be used to predict nutrient requirements. The ADEQUATE group will receive grass hay to meet but not exceed the required net energy for maintenance (NEm) and metabolizable protein. The RESTRICTED group will be fed a grass hay-wheat straw blend that supplied 80% of the NEm required by the ADEQUATE group. The ABUNDANT group will be fed a diet composed of grass hay, soybean hulls, and dry-rolled corn to supply 150% of the NEm required by the ADEQUATE group. These dietary treatments were chosen on the basis that such differences in nutrient intake may be encountered among cattle supplemented or not during limited pasture resources. Dietary treatments will be applied to animal groups during a 95-d period that correlated to the second trimester of gestation, as this is the time where muscle cell and adipocyte development in the fetus is reported to occur, and a common time during gestation when limited pasture resources can occur for spring-calving cow herds in the Northern Great Plains region. Liver, muscle, and adipose tissues will be collected from a group of fetuses immediately following the gestational treatment period, and from survival fetuses at weaning, and at harvest. All tissue samples will be immediately snap-frozen in liquid nitrogen and stored for subsequent extraction of mRNA for expression analyses (RT-PCR) and determination of protein abundance (Western blotting) for target genes involved in the regulation of body composition. Standard growth performance and carcass characteristics will measured on the animals in the surviving fetus groups and related to differences in gene expression and protein abundance. To evaluate nutrient by genotype interactions, a blood sample from steer calves will be collected and DNA will be isolated from each animal's whole blood using a commercially-available blood DNA isolation kit (DNAzol-BD, Molecular research Center, Cincinnati, OH). The DNA quantity and quality will be evaluated using a Nanodrop ND-1000 spectrophotometer. The DNA sample will be used to determine ghrelin genotype. The Ghrelin SNP A/G (Sherman et al., 2008) will be genotyped with a custom TaqMan Genotyping Assay (Applied Biosystems, Foster City, CA). TaqMan genotyping assays include 2 fluorescently labeled probes VIC and FAM, which are markers for the 2 SNP alleles A and G. The Ghrelin SNP and flanking sequence will be submitted to Applied Biosystems, which will subsequently design primers and probes for the TaqMan assay. TaqMan genotyping MasterMix (Applied Biosystems) will be mixed with custom primers, probes, and DNA samples in 96 well plates and then the plates will be loaded onto a thermocycler for amplification of the SNP locus. Following amplification, samples will be loaded onto a Stratagene real-time thermocycler (Agilent Technologies, Santa Clara, CA) to read the presence of the dyes (VIC, FAM, or both) in the reaction. Cattle of various genotypes will be paired with their respective growth performance, carcass characteristic, and carcass chemical composition data.