Saroj Kumar Sahoo

Multiple linear correlation and prediction of lifetime performance on the basis of first lactation fertility and production traits in Karan Fries (Holstein Friesian crossbred) cattle

Higher productions along with superior fertility are the functions of greater stayability of dairy cattle in the herd. Present investigation was undertaken to evaluate lifetime traits and their prediction on the basis of first lactation traits in Karan Fries cows maintained at National Dairy Research Institute. Data of 5878 lactation records of 1988 adult cows pertaining to the period between 1978 to 2012, were collected for analysis. The phenotypic and genetic correlations of first lactation with lifetime traits were estimated and lifetime performance was predicted using backward elimination multiple linear regression models. Cumulative milk yield (CMY) analysis indicated that the Karan Fries cows achieved around 85% of their lifetime production by 4 th lactation. Phenotypic and genetic correlations of lifetime production traits were positive with first lactation production traits, whereas the association was negative with first lactation fertility traits. The coefficient of variation and mallows Cp criterion estimates of better fit models were lower and ranged between 12 to 18% and 2.51 to 6.00, respectively. Results indicated that the first lactation traits used for the prediction, best explained the variation in traits such as Lifetime yield upto two lactations (51.00%) and breeding efficiency (51.43%), on the basis of coefficient of determination (R 2 )estimates. Regression models for predicting lifetime yield upto three lactations, milk yield per day of productive life and lifetime daughter pregnancy rate had moderate coefficient of determination estimates.

Estimation of Genetic Parameters for First Lactation Monthly Test-day Milk Yields using Random Regression Test Day Model in Karan Fries Cattle

A single trait linear mixed random regression test-day model was applied for the first time for analyzing the first lactation monthly test-day milk yield records in Karan Fries cattle. The test-day milk yield data was modeled using a random regression model (RRM) considering different order of Legendre polynomial for the additive genetic effect (4th order) and the permanent environmental effect (5th order). Data pertaining to 1,583 lactation records spread over a period of 30 years were recorded and analyzed in the study. The variance component, heritability and genetic correlations among test-day milk yields were estimated using RRM. RRM heritability estimates of test-day milk yield varied from 0.11 to 0.22 in different test-day records. The estimates of genetic correlations between different test-day milk yields ranged 0.01 (test-day 1 [TD-1] and TD-11) to 0.99 (TD-4 and TD-5). The magnitudes of genetic correlations between test-day milk yields decreased as the interval between test-days increased and adjacent test-day had higher correlations. Additive genetic and permanent environment variances were higher for test-day milk yields at both ends of lactation. The residual variance was observed to be lower than the permanent environment variance for all the test-day milk yields.