Studies on Lactation Length in Gir Triple Cross Cows

The present investigation was carried out from the data collected on milk production performance of 410 Gir triple cross cows having 1182 lactation records maintained at R. C. D. P. on Cattle, M. P. K. V., Rahuri (Maharashtra) over a period of 35 years (1977 to 2011). The overall least squares means of lactation length in Gir triple cross cows was 350.72 ± 5.31 days. The effect of period of calving on lactation length was significant (P < 0.01). The effect of season of calving, lactation order, age at first calving and sire was non-significant. The heritability of lactation length was 0.019 ± 0.010. The phenotypic correlation of lactation length with lactation milk yield was non-significant, with 300 days milk yield was significant (P<0.05), with peak milk yield negative and significant (P<0.05), and with days to attained peak milk yield negative and non-significant. The genetic correlation of lactation length with lactation milk yield and 300 days milk yield was significantly positive, with peak milk yield and days to attain peak milk yield highly significant and negative.