Intensified use of TAI and sexed semen on commercial farms

Influence of Ovarian Status and Steroid Hormone Concentration on Day of Timed Artificial Insemination (TAI) on the Reproductive Performance of Dairy Cows Inseminated with Sexed Semen

This study aimed to evaluate the effect of the ovarian status and steroid hormone concentration on the day of TAI on the reproductive performance of dairy cows subjected to estrus synchronization treatment and timed artificial insemination with sexed semen. Seventy-eight cyclic Holstein cows pre-treated with PGF2α-GnRH were divided in two groups-I (Preselect-OvSynch, n = 38) and II (OvSynch+PRID-7-day+eCG, n = 40)-and inseminated with sexed semen. The presence of preovulatory follicle (PF) with or without corpus luteum (CL), the PF diameter, the estradiol (E₂) and progesterone (P₄) concentrations on the day of TAI, the pregnancy rate (PR) and embryo loss were determined. On the day of TAI, 78.4% of all the pregnant cows presented a PF (mean size 1.80 ± 0.12 cm) without CL, low P₄ (0.59 ± 0.28 ng/mL) and high E₂ (12.35 ± 2.62 pg/mg) concentrations. The positive correlation between the size of the PF and the level of E₂ in the pregnant cows from group II was stronger than that of group I (R = 0.82 vs. R = 0.52, p < 0.05). The pregnancy rate on day 30 (57.5% vs. 36.8%) and day 60 (50% vs. 26.3%; p < 0.05) and the embryo losses (13% vs. 28.5%) showed better effects of treatment in group II. In conclusion, the ovarian status and the steroid hormone concentration on the day of TAI influence the pregnancy rates of dairy cows subjected to estrus synchronization and timed artificial insemination with sexed semen.

Application of gender-ablated semen during timed artificial insemination following oestrous synchronization in dairy and beef cows

The objectives of this study were to compare oestrous synchronization expression and conception rate following timed artificial insemination (TAI) with frozen-thawed X-sexed or unsexed semen in dairy and beef cows. For this study, 227 cows (dairy, n = 130 and beef, n = 97) were assigned to a 9-day Ovsynch + controlled intravaginal drug release (CIDR) protocol. All cows were TAI using X-sexed or unsexed semen from 8 sires. Each semen type was obtained from 4 sires [2 dairy (Holstein Friesian) and 2 beef (Angus)]. Pregnancy detection was performed on Days 35, 65 and 95 following TAI by transrectal ultrasonography and hand palpation. The proportion of oestrus expression was higher in dairy (85.3%) cows compared with beef (65.0%) cows (p < .05). Overall, dairy (X-sexed, 61.9% and unsexed, 62.0%) cows had greater conception rates on Day 35 compared to beef (X-sexed, 56.0% and unsexed, 52.2%) cows (p < .05). Concurrently, on Day 95, overall conception rates in dairy (X-sexed, 41.4% and unsexed, 48.5%) cows were greater than beef (X-sexed, 38.0% and unsexed, 37.0%) cows (p < .05). Pregnancy/embryo losses between Days 35 and 65 in dairy (X-sexed, 33.3% and unsexed, 18.2%) cows and beef (X-sexed, 28.6% and unsexed, 29.2%) cows were recorded (p < .05). Dairy (X-sexed, 7.7% and unsexed, 8.3%) cows had higher incidence of pregnancy losses between Days 66 and 95 when compared to beef (X-sexed, 5.0% and unsexed, 0.0%) cows (p < .05). Oestrous expression and conception rates in dairy and beef cows were satisfactory. Advanced reproductive biotechnologies can successfully utilize gender-ablated semen in organized emerging cattle farming systems.

Revisiting the Timing of Insemination at Spontaneous Estrus in Dairy Cattle

Cows show spontaneous estrus over 8-20 h but become refractory to the bull about 10-12 h before ovulation. This indicates that ovulation occurs 10-12 h after the end of estrus behavior, yet spermatozoa from the bull ejaculate need to undergo maturation and capacitation for 6 to 8 h in the female reproductive tract before they are capable of fertilization. Traditionally, the onset of estrus has been considered the best timing for artificial insemination (AI) in cattle, that is, 6 to 24 h from the first signs of estrus. However, recent findings suggest this interval should be reduced to 16 to 6 h before ovulation, bringing it closer to the end of estrus. In this review, the end of estrus rather than its onset is proposed as the best guide for AI timing in dairy cattle, and physiological indicators of late estrus are discussed such as relaxation of the intravaginal part of the uterus, a lower cervical mucus viscosity and a softer pre-ovulatory follicular consistency as simple cues indicating a cow is ready for service.