Estimation of genetic parameters of first lactation 305-day and monthly test-day milk yields in Karan Fries cattle

摘要

The present investigation was carried out using first lactation 16,184 monthly test-day milk yields (MTDMYs) records of 1,583 Karan Fries cattle that calved from 1983 to 2012 sired by 130 bulls maintained at ICAR-National Dairy Research Institute, Karnal. Mixed model analysis was carried out by least-squares maximum likelihood programme to study the effects of genetic and non-genetic factors on first lactation 305-day milk yield (FL305DMY) and MTDMYs record of Karan Fries cattle. The highest and lowest MTDMYs were observed in TD-2 (12.95 kg) and TD-10 (9.72 kg), respectively. The average FL305DMY was 3123 kg. The effect of season of calving was found to be highly significant on all the MTDMYs while non-significant effect was observed on FL305DMY. Period of calving had non-significant effect on most of the MTDMYs and on FL305DMY, whereas; the effect of age at first calving was highly significant on majority of the MTDMYs and on FL305DMY. The heritability estimates for FL305DMY was 0.35 +/- 0.07 and for MTDMYs it ranged from 0.11 (TD-11) to 0.34 (TD-6). The genetic and phenotypic correlations among MTDMYs and with FL305DMY were found to be highly significant. The estimates of phenotypic and genetic correlations among all the MTDMYs ranged from 0.15 (TD-1 and TD-11) to 0.83 (TD-8 and TD-9) and 0.29 (TD-1 and TD-10) to 0.99 (TD-2 and TD-3), respectively. High phenotypic and genetic correlations of TD-3 (0.69 and 0.91) and TD-4 (0.65 and 0.99) with FL305DMY indicated that these key test-day yields could be used for the early and accurate selection of animals resulting in faster genetic gain.