Factors associated with fertility of nulliparous dairy heifers following a 10-day fixed-time artificial insemination program with sex-sorted and conventional semen

Abstract

Objective: To examine factors associated with fertility on dairy farms that used a common fixed-time artificial insemination (FTAI) program in yearling heifers. Methods: Records were analysed from 954 yearling heifers on 10 south-west Victorian dairy farms that used a common FTAI program, involving the insertion of a 1.9-g progesterone-releasing device for 10 days; 2mg oestradiol benzoate at insertion; 500 μg cloprostenol on day 7; and FTAI 48 h after device removal. Weight, age, expression of oestrus, sire, semen type (frozen sex-sorted or frozen conventional) and timing of insemination were examined for their relationship with first-service conception rates. Results: Heifers over 300kg bod..