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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Environmentally Integrated Dairy Management Research » Research » Research Project #427527

Research Project: Determining the Biological Basis of Genetic Variation in Forage and Feed Utilization Efficiency in Lactating Dairy Cattle

Location: Environmentally Integrated Dairy Management Research

Project Number: 5090-12630-005-11-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 1, 2014
End Date: Aug 31, 2019

Objective:
Objective 1: To evaluate genomic and phenotypic databases regarding the biological causes of between-family variation in residual feed intake (RFI) and its component traits. Objective 2: To assess the impact of genomic selection for RFI on the forage and feed utilization efficiency of growing dairy heifers and the feeding behavior and body tissue deposition and mobilization characteristics of lactating dairy cows.

Approach:
For Objective 1: a) Use published information about dietary ingredients, as well as cohort-based estimates of energy density of experimental diets, to investigate the existence and type(s) of genotype by diet interactions; b) Determine the likely direct and correlated responses to selection for residual feed intake (RFI) in lactating dairy cattle using structural equation models to reveal causal relationships between RFI, its component traits, and other economically important traits; c) Evaluate different approaches regarding multiple-step corrections and covariate inclusion required for the inference of genomic predictors of RFI and compare such approaches for genomic predictive ability and the ability to identify genetic effects; and d) Complete the transition from preliminary genomic evaluations for feed efficiency to routine genomic evaluations of Holstein bulls, cows, heifers, and calves that can be used for selection and management decisions on U.S. dairy farms. For Objective 2: a) Evaluate the efficiency of forage and feed utilization in growing dairy heifers at the cooperator's facility, using replicated pens of heifers with high, intermediate, or low genetic merit for RFI, using genomic estimated breeding values (GEBV) previously obtained; b) Investigate associations between early and late lactation feeding behavior of first and second lactation cows with high, intermediate, or low genetic merit for RFI, based on GEBV, using feeders at the cooperator's facility, and feeders at the ARS facility in Prairie du Sac, WI; c) Quantify differences in body tissue deposition and mobilization throughout the lactation in first and second lactation cows of high, intermediate, or low genetic merit for RFI, using GEBV, body condition scores, and ultrasound-based measurements taken from pre-calving throughout the lactation until subsequent calving.