Heifers are the future cows of the herd. Moreover, the heifers are considered as the most important animals in cattle herd, as they are replacement animals. The investment on the heifers is considered as the investment in the future. Sahiwal is one of the superior milch breeds of India, and the breed is well known for its remarkable milk production, heat tolerance, disease resistance and low maintenance cost. Slow growth, delayed puberty and late attainment of sexual maturity in zebu heifers have been major constraints in maximizing their production efficiency. With an overall objective of improving reproductive efficiency of Sahiwal heifers, the present investigation was carried out. The data spanning ten years (January, 1996 – December, 2005) of the Sahiwal herd maintained at NDRI, Karnal were analysed for reproductive performance. The least squares analysis was used to assess the effects of the season of birth and birth weight on the reproductive traits, namely age at first service, age at first conception, age at first calving and numbers of services per conception. The mean age at first service, first conception, first calving and number of services per conception were 780.26 ± 7.35, 833.90 ± 9.71, 1107.39 ± 8.91 days and 1.88 ± 0.07 respectively. The effect of season of birth was significant on age at first service, age at first conception  and age at first calving. The birth weight had significant effect on number of services per conception.

Highlights

• The effect of season of birth was significant on age at first service, age at first conception and age at first calving.
• The birth weight had significant effect on number of services per conception.
• The season of birth and birth weight should be taken into consideration during the selection of the Sahiwal heifers for the reproductive traits.