摘要 : The data for the present investigation were collected from history sheets of crossbred cattle maintained at Instructional dairy farm, Nagla of G.B. Pant. Univ. of Agric. & Tech, Pantnagar. The data pertained to 1170 crossbred catt... 展开 The data for the present investigation were collected from history sheets of crossbred cattle maintained at Instructional dairy farm, Nagla of G.B. Pant. Univ. of Agric. & Tech, Pantnagar. The data pertained to 1170 crossbred cattle from progeny of 65sires were distributed over a period of 35 years from 1970 to 2004. The overall mean of age at first calving, first lactation milk yield, first lactation period, first dry period, first calving interval, first service period, herd life, productive life,total lactation length, lifetime milk, yield and lifetime milk yield/day of productive life were 1350.52±13.48 (days), 3093.65±37.17 (days), 361.42±3.61 (days), 177.20±6.47 (days), 538.60±6.66 (days), 271.32±0.75 (days), 1633.22±20.56 (days), 1515.75±20.S6 (days), 1305.18±20.37 (days), 9234.45±133.75 (kg) and 6.85±0.14 (kg) respectively. The effect due to season of calving on all the first lactation and lifetime traits was found to be non significant. The effect due to period of calving on all the first lactation traits was highly significant (P<0.01) except first dry period and first service period. The heritability estimates for age at first calving, first lactation milk yield, first lactation period, first dry period, first calving interval, first service period, herd life, productive life, total lactation length, lifetime milk yield and lifetime milk yield / day of productive life were 0.20±0.05, 0.23±0.06, 0.26±0.06, 0.18±0.05, 0.16±0.05, 0.15±0.05, 0.30±0.07, 0.19±0.07, 0.24±0.07, 0.23±0.06 and 0.27±0.05 respectively. The genetic and phenotypic correlations among first lactation traits, between first lactation and life time performance traits and among life time performance traits were found from very low to very high. These correlations indicated that selection on the basis of first lactation milk yield would bring desirable improvement in lifetime milk yield and lifetime milk yield/ productive life. 收起