Abstract
Records of 364 Holstein Friesian cows were analyzed to study the fixed effect of age at first calving, first lactation milk yield, season and year of birth on lifetime traits using general linear model. The overall least squares means were 2,864±63 days, 1,638±58 days, 3.55±0.12, 1.68±0.07, 1.12±0.06 and 0.56±0.03 for longevity, productive herd life, total calves, female calves, selective values and coefficient of gene replication. The cows with >1,500 kg first lactation milk yield had minimum longevity of 2,170±329 days as well as shortest productive herd life of 869±330 days. Cows calved at early age had lowest productive herd life of 919±366 days. Lesser number of total and female calves was produced by cows with very short age at first calving. Cows with intermediate first lactation milk yield (2,066–3,195 kg) produced more normal and female calves. Selective values and coefficient of gene replications were not statistically affected by the above non-genetic factors. Year of birth highly influenced all the traits. The study showed that better nutrition and follow-up is needed for cows calving at early age.
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