Use of Random Regression Test-day Model for First Lactation Test-day Milk Yield in Mehsana Buffalo

A total of 32,123 first lactation test-day milk yield (TDMY) records of 8,023 Mehsana buffalo sired by 118 sires from 2012 to 2019 (8 years) of Mehsana buffalo retrieved from information network for animal productivity & health (INAPH) was considered and analyzed in the present study. Heritability, variance and covariance components for TDMY were estimated using average information restricted maximum likelihood (AIREML) algorithm of legendre polynomials (LP) of 2nd order to transform days in yield. A random regression test day model (RRTDM) is used to estimate the parameters. Modeling of lactation curves for monthly TDMY and milk constituents were done using AIREML algorithm. The heritability and repeatability estimates for TDMY were observed lower (0.20) and higher (0.84) respectively. The additive genetic correlations were found higher than the phenotypic correlations among different test-days (TD). The higher values of genetic and phenotypic correlations were observed between adjacent TD records in the beginning but slightly lower at the end of lactation.