Genetic and Phenotypic Parameters for a Profit Function and Selection Method for Optimizing Profit in Dairy Cattle

Abstract

Genetic and phenotypic relationships were estimated on a profit function for 933 Holstein cows. Methods of selection among cows were investigated for profit per day of herdlife. The profit function included production, reproduction, and body weight. Heritability for profit/day during 1st lactation was .50 .+-. .12 compared to .28 .+-. .10 for milk/day in the 1st lactation. Correlations (genetic, phenotypic) between 1st lactation and lifetime records per day of herdlife were (.93, .74) for milk production and (.79, .65) for profit. Correlations between milk/day-1st and profit/day-life were (.85, .55). Correlations for total lifetime production and profit were (.95, .97) and per day of herdlife were (.94, .87). Herdlife compared to lifetime traits had larger correlations with profit/day than yield/day (.64 vs. .40, .69 vs. .48) indicating the profit function contained important factors related to herdlife besides lactation performance. Correlations between age at first calving with total lifetime production and profit were negative (-.15 to -.32, -.16 to -.07), suggesting an increase in these traits can be expected in selection for younger age at 1st calving. Genetic gain expected in profit/day of life from selection on profit/day-1st lactation was 24% more efficient than milk/day-1st. A simplified profit function may be effective for increasing profitability in dairy production by selection.