Performing Department
Animal Science
Non Technical Summary
Efficiency of feed utilization is very important to producer profitability, especially in times of increased input (feed and land) costs. Previous research has indicated that individual animals vary in residual feed intake (RFI), a measure of feed efficiency that is moderately heritable. Despite this, many physiological mechanisms of RFI remain unclear, and the effects of selection for RFI in the cow herd are not known. Studies in this project will increase knowledge of both physiological mechanisms and production implications of RFI. These may allow for improved production practices to increase the efficiency of beef cattle production in the US.
Animal Health Component
0%
Research Effort Categories
Basic
10%
Applied
90%
Developmental
(N/A)
Goals / Objectives
To understand biological sources of variation in efficiency of feed utilization.
To develop producer educational programs to enhance technology adoption by the beef industry.
To discover physiological biomarkers and genetic markers for feed efficieny.
Project Methods
Commercial black cows will be bred by A.I. to Hereford bulls selected for either high or low RFI and have acceptable traits to produce females for the existing herd. The overall goal is to produce moderate framed black baldy cows that can thrive in the High Plains region. Continental bulls (Simmental) will be used as a terminal cross for clean up.Using the GrowSafe system, feed efficiency information will be collected on all heifers, and any steer calves retained for other projects. The efficiency trait of greatest interest is residual feed intake, or RFI. Residual feed intake is defined as the difference between actual feed intake and expected feed intake of the animal. By definition, animals consuming less feed than expected are negative for RFI, and have a greater efficiency than positive RFI animals. One goal of this project is to test all potential herd sires and utilize bulls that are divergent for RFI (high RFI and low RFI). Progeny from those sires will be similarly measured for RFI to estimate heritability.Herd management for this project includes:a) Evaluating and documenting sire EPD values for backfat (BF), ribeye area (REA, in2), and percent intramuscular fat (%IMF), an indication of marbling. Sire selection and heifer retention decisions will be made so that both high RFI and low RFI groups are not biased in relation to carcass traits.b) All heifers will be ultrasounded at approximately 12 months of age, documenting liveweight, BF, REA and %IMF values.Objective 1 of this study also aims investigate the relationship of feed efficiency and ruminant gastrointestinal tract size as well as small intestinal growth, vascularity, and function. We hypothesize that a portion of the individual differences in RFI can be attributed to gastrointestinal tract (and especially small intestine) size, growth, and function. Using tissues collected from these animals, we will investigate the relationship of RFI with the gastrointestinal organ empty weight and length (intestine only), as well as small intestinal indices of growth, vascularity, and function including cellularity (DNA, RNA, and protein concentration), gene expression, and histological measures of proliferation, morphology, and vascularity. Attainment of puberty prior to the breeding season will be documented in all heifers via blood sampling (circulating progesterone concentrations) beginning post-weaning. Conception rate to AI, overall breeding season conception rates, retention in the herd, and longevity will be documented.For this project, relationships between behavior and feed efficiency traits will be estimated for both heifers and bulls. Differences between sexes will be compared. Aggression-type traits will also be studied, such as competition (i.e. rank among bulls/heifers in pen to determine hierarchy) and feeding aggressiveness (i.e. bunk occupation time, bite force, etc.).