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

Increased fertility was associated with larger heifers and heifers that expressed oestrus, particularly when sexed-sorted semen was used. Variation in the timing of AI with respect to device removal between 47 and 51.4 h did not adversely affect conception rates.