IMPROVEMENT IN MILK PRODUCTION POTENTIAL BY SELECTION BASED ON EARLY EXPRESSED ECONOMIC TRAITS IN CROSSBREDS

摘要

The correlated response to selection in first lactation yield and lifetime milk production traits is indirect when the selection is applied to early expressed different economic traits in dairy animals. But major gain one can get by way of increased genetic progress by permitting the early identification of superior germplasm. The present study was conducted on 1017 first lactation records of Holstein X Sahiwal crossbreds maintained at three Military Dairy Farms viz., Mhow, Jabalpur and Allahabad, spread over 20 years (1972 to 1991). On the basis of Holstein inheritance the animals were classified into 4 grades viz., 3/8, 5/8, 3/4 and 7/8. The indirect correlated response in first lactation milk yield is measured by applying the selection to birth weight, age at first conception, age at first calving, first lactation lengtb, first dry period, first calving interval, milk yield per day of lactation length and milk yield per day of calving interval. The expected correlated response of first lactation milk yield (Y) was obtained by the formula (Falconer, 1989).