Estimates of genetie parameters using random regression test day model for first lactation milk yield in Murrah buffaloes

Abstract

A single-trait random regression model that contains both fixed and random regression coefficients was applied for the first time for analyzing test day milk yield records of first lactation milk yield in Murrah buffaloes. Heritabilities of test day milk yield varied fram 0.33 to 0.58 in different test days. The highest heritability was the initial test day (fifth day) milk yield, Genetic correlations among test day milk yields were higher in the initial test day milk yield and decreased when the test day interval were increased. The magnitude of genetic correlations between test day yield and 305 day in milk varied from 0.25 to 0.99, indicated a minimum of 215-245 first lactation length is required for genetic evaluation of Indian Murrah buffaloes. The accuracy of the model was judged by predicted error and the reliability of predicting milk yield using the developed model varied from 89 to 94% in different test days.