Fertility in dairy cows after artificial insemination using sex-sorted sperm or conventional semen.

The aim of this study was to compare pregnancy per artificialinsemination (P/AI) after timed AI with sex-sorted sperm (SS)or conventional semen (CS) in lactating dairy cows. Cycliccows (n = 302) were synchronized by Ovsynch and randomlyassigned into two groups at the time of AI. Cows with a folliclesize between 12 and 18 mm and clear vaginal dischargeat thetime of AI were inseminated with either frozen-thawed SS(n = 148) or CS (n = 154) of the same bull. A shallow uterineinsemination was performed into the uterine hornipsilateral tothe side of probable impending ovulation. Pregnancy per AIon Day 31 tended (p = 0.09) to be less for SS (31.8%) than CS(40.9%). Similarly, P/AI on Day 62 was less (p = 0.01) forcows inseminated with SS (25.7%) compared with CS (39.0%).The increased difference in fertility between treatments fromDays 31 to 62 was caused by the greater (p = 0.02) pregnancyloss for cows receiving SS (19.2%) than CS (4.8%). Cow parity(p= 0.02) and season (p < 0.01) when AI was performed wereadditional factors affecting fertility. Primiparous cows hadgreater P/AI than multiparous cows both on Day 31 (41.7% vs25.0% in SS and 53.0% vs 31.8% in CS groups) and on Day62 (33.3% vs 20.5% in SS and 48.5% vs 31.8% in CS groups).During the hot season of the year, P/AI on Day 31 wasreduced (p = 0.01) in the SS group (19.6%) when comparedwith the rates during the cool season (38.1%). In conclusion,sex-sorted sperm produced lower fertility results compared toconventional semen even after using some selection criteria toselect most fertile cows.