Effect of equine chorionic gonadotropin treatment during a progesterone-based timed artificial insemination program on reproductive performance in seasonal-calving lactating dairy cows

Abstract

The aim of this study was to investigate the effect of progesterone (P4)-based timed artificial insemination (TAI) programs on fertility in seasonal-calving, pasture-based dairy herds. A total of 1,421 lactating dairy cows on 4 spring-calving farms were stratified based on days in milk (DIM) and parity and randomly allocated to 1 of 3 treatments: (1) control: no hormonal treatment; cows inseminated at detected estrus; (2) P4-Ovsynch: cows received a 7-d P4-releasing intravaginal device (PRID Delta; CEVA Santé Animale, Libourne, France) with 100 μg of a gonadotropin-releasing hormone (GnRH) analog (Ovarelin; CEVA Santé Animale) at PRID insertion, a 25-mg injection of PGF (Enzaprost; CEVA Santé Animale) at PRID removal, GnRH at 56 h after device removal and TAI 16 h later; (3) P4-Ovsynch+eCG: the same as P4-Ovsynch, but cows received 500 IU of equine chorionic gonadotropin (eCG; Syncrostim; CEVA Santé Animale) at PRID removal. At 10 d before mating start date (MSD), all cows that were ≥35 DIM were examined by transrectal ultrasound to assess presence or absence of a corpus luteum; body condition score (BCS) was also recorded. Pregnancy diagnosis was performed by transrectal ultrasonography 30 to 35 d after insemination. Overall pregnancy/AI (P/AI) was not different between groups (50.9, 49.8, and 46.3% for control, P4-Ovsynch, and P4-Ovsynch+eCG, respectively) but the 21-d pregnancy rate was increased by the use of synchronization (35.0, 51.7, and 47.2%, respectively). Compared with the control group, synchronization significantly reduced the interval from MSD to conception (34.6, 23.0, and 26.5 d, respectively) and consequently reduced the average days open (98.0, 86.0, and 89.0 d). Across all treatment groups, DIM at the start of synchronization affected P/AI (42.3, 49.5, and 53.9% for <60, 60-80, and >80 DIM, respectively), but neither parity (46.5, 50.4, and 48.4% for parity 1, 2, and ≥3, respectively) nor BCS (44.0, 49.4, and 58.6% for ≤2.50, 2.75-3.25, and ≥3.50, respectively) affected the likelihood of P/AI. Two-way interactions between treatment and DIM, parity, or BCS were not detected. In conclusion, the use of TAI accelerated pregnancy establishment in cows in a pasture-based system by reducing days open, but eCG administration at PRID removal did not affect P/AI.

Evaluation of delayed timing of artificial insemination with sex-sorted sperm on pregnancy per artificial insemination in seasonal-calving, pasture-based lactating dairy cows

“…This presumably reflects the presence of a larger population of viable sperm in the female reproductive tract at the time of ovulation. Ovulation synchronization and TAI have been extensively evaluated in seasonal-calving systems, and have been shown to shorten the interval from the start of the breeding period to pregnancy establishment compared with nonsynchronized animals (Herlihy et al, 2011;Randi et al, 2018). The objective of this study was to evaluate the effect of timing of AI on P/ AI for SS in a pasture-based, compact calving production system.…”

Probability of pregnancy to artificial insemination either after detected oestrus or at a fixed time in dairy cows: Influence of intrinsic and extrinsic factors in a large‐scale, on‐farm study

“…The present study includes a permanent system for oestrus detection and AI of those cows coming into oestrus, irrespective of their previous reproductive procedures. Although FTAI treatments were originally developed to avoid oestrous detection, these results demonstrate that these treatments also increase the number of cows that can conceive at the beginning of the breeding season (Randi et al., 2018). The inclusion of FTAI in practical reproductive management systems may also have a great impact in reducing calving interval, thus, making more effective the use of superior genetic sires and increasing annual milk production.…”

Economics of timed artificial insemination with unsorted or sexed semen in a high-producing, pasture-based dairy production system

“…It was assumed that TAI was only administered a single time at the start of the breeding period for first service only and for all females selected to be bred. A P4-Ovsynch protocol was chosen as this has been shown, including in several recent studies from Ireland, to result in excellent fertility (Randi et al, 2018;Sánchez et al, 2018). It is now well accepted that inclusion of a P4 device, or use of a strategy to induce elevated P4 (e.g., induction of an accessory corpus luteum), into a standard Ovsynch protocol is beneficial due to the known positive effects of elevated P4 during the growth of the ovulatory follicle (Pursley and Martins, 2011;Rivera et al, 2011).…”

“…Numerous TAI programs exist, many now in use are variations on the Ovsynch protocol (Pursley et al, 1995) frequently including progesterone (P4; Pursley and Martins, 2011). Such programs increase the likelihood of earlier concep-Economics of timed artificial insemination with unsorted or sexed semen in a high-producing, pasture-based dairy production system tion compared with estrus detection and AI (Herlihy et al, 2011;Randi et al, 2018). Similarly, Giordano et al (2011) concluded that TAI improved reproductive performance and resulted in a profit advantage over estrus detection and AI.…”