ENHANCED DAIRY HERD PROFITABILITY THROUGH DEVELOPMENT OF SELECTION TOOLS AND IDENTIFICATION OF METABOLIC PROFILES THAT OPTIMIZE FEED EFFICIE

The objectives of the study are to identify DNA markers and physiological profiles that contribute to genetic variation in feed intake, and to determine the association of feed intake with genetic evaluations for milk yield and body conformation. The single largest cost of dairy production is feed and rising prices for animal feed limit dairy farm profitability. There has been no direct genetic selection for feed efficiency in the dairy industry due to limited availability of feed intake estimates for individual cows. Opportunities now exist to develop DNA markers for feed efficiency that will require fewer individual feed intake measures than traditional selection techniques. This study proposes to measure feed intake on 1,000 Holsteins that are fed individually. Feed and refusals will be weighed for each cow once per month. Blood samples will be taken and analyzed for health indicators. Data from the field trial herds will be combined with daily feed intake from heifers and lactating cows that were part of nutritional trials at Penn State. Feed efficiency will be estimated as the ratio of milk energy to feed energy and as residual feed intake. Feed efficiency measures will then be associated with a DNA marker panel. Metabolic profiles from blood and milk assays will also be associated with efficiency to identify potential nutrition and management strategies that optimize feed efficiency without compromising cow health. The economic analysis will consider varying income and expenses for different genotypes. Genetic evaluations for yield and type traits will also be regressed on feed intake data to refine estimates of change in marginal feed costs as a response to genetic selection.