Relationship of First Lactation Performance to Lifetime Production and Economic Efficiency

Abstract

The relationship between yield in first lactation and lifetime performance and estimated economic return was studied on 933 Holstein cows to determine the marginal effects of increasing first lactation production. Polynomial regressions (3°) on yield in first lactation accounted for 1.7 to 11.4% of the variation in traits of lifetime. Yield in first lactation accounted for 31.4 and 62.3% of the variations in milk/day of life and profit/day of life. Increases in daily yield of first lactation beyond a point do not lead to additional increases in total or daily lifetime production or economic return. Maximal total or daily lifetime performance occurred in the range of 19 to 22 kg milk/day during the first lactation. Profit/day of first accounted for more variation in profit for life (16.3 versus 11.4%) and profit/day of life (42.9 versus 31.4%) than did milk/day of first. Daily performance traits in first lactation accounted for only 1.7 to 3.5% of the variation in herdlife and 6.9 to 8.3% of the variation in milk for life. A significant positive linear trend existed between profit/day of first and lifetime traits. This study indicates an estimated profit function can be important as an aid to economic evaluation among dairy cows. © 1976, American Dairy Science Association. All rights reserved.