Evaluation of Conventional vs Sexed-sorted Semen for Fixed-time Artificial Insemination During a 14-day Estrous Synchronization in Mature Beef Cows

Abstract Reproduction is essential to the productivity of all cow-calf operations and artificial insemination (AI) has become a valuable tool for producers to increase genetic improvement. Incorporating sexed semen into AI programs allows producers to shift or control the gender ratio of their calf crop for genetic or economic advantages. However, sexed semen is not widely used due to concern of reduced conception rates and increased costs. Our hypothesis is that pregnancy rates to fixed timed artificial insemination (FTAI) using sex-sorted semen following a 14-day synchronization protocol would be similar to that of conventional semen. Therefore, the objective of this study was to compare pregnancy rates in cows inseminated following a 14-day controlled internal drug release (CIDR) protocol with frozen semen from 2 sires each stored conventionally or female sex-sorted. Commercial Angus cows (n = 200) at the University of Arkansas Beef Cattle Research Unit in Fayetteville, Arkansas were allocated randomly to 1 of 2 treatment groups by pre-breeding weight and body condition score (BCS), as well as calving date, cow age, and parity. Treatment groups were 1) cows (n = 100) received conventional semen; 2) cows (n = 100) received sexed-sorted female semen, with the 2 sires represented in each treatment. All cows were synchronized using a CIDR (1.38g progesterone, Zoetis Kalamazoo, MI) inserted intravaginally on d -14 of the protocol simultaneously to administration of prostaglandin F2α (PGF; 25 mg dinoprost tromethamine; Lutalyse HighCon, Zoetis). On day -6, gonadotropin-releasing hormone (GnRH; 100 µg gonadorelin; Factrel, Zoetis) was administered. On day 0, PGF was administered simultaneously to CIDR removal and heat detection patches (Estrotect; Rockway, Inc., Spring Valley, WI) were applied. FTAI and administration of GnRH occurred 66 hours post CIDR removal. Estrus expression was determined by scoring the heat detection patch and assumed estrual if greater than 50% of the coating was removed. Uterine tone scores were determined on a scale of 1 to 4, with 1 being flaccid and 4 being turgid. Pregnancy rates, estrus expression, and tone scores were analyzed using the GLIMMIX procedure in SAS 9.4 with sire and block as random effects. The PROC FREQ procedure was used to assess the number of pregnant and open cows in each treatment. There were no differences in FTAI pregnancy rates (P = 0.71), estrus expression (P = 0.88), or tone scores (P = 0.27) between treatments. Cows bred to conventional semen had a 74% conception rate and cows bred to sex-sorted semen had a 72% conception rate to FTAI. These data suggest that sex-sorted semen preforms comparably to conventional semen when used in a 14-day synchronization program.