Interventions After Artificial Insemination: Conception Rates, Pregnancy Survival, and Ovarian Responses to Gonadotropin-Releasing Hormone, Human Chorionic Gonadotropin, and Progesterone

Abstract

We hypothesized that increasing concentrations of progesterone (P4) after artificial insemination would increase fertility. Our objective was to assess changes in ovarian structures, incidence of ovulation, and change in serum P4 in response to GnRH, human chorionic gonadotropin (hCG), or exogenous P4 (controlled internal drug release; CIDR insert) treatment beginning 4 to 9 d after artificial insemination (d 0) and again 7 d later (experiment 1). Blood was collected from 753 cows in 3 herds on d 0 and 7. Ovaries of 162 cows were scanned and mapped to confirm the presence of a corpus luteum (CL), and cows were assigned randomly to serve as controls (n = 41) or to receive a CIDR insert for 7 d (n = 41), 100 microg of GnRH (n = 40), or 3,300 IU of hCG (n = 40). More cows were induced to ovulate in response to GnRH (60%) and hCG (78%) compared with controls (2.4%). Compared with controls, cows treated with GnRH or hCG had more induced CL (d 7) and more total CL (d 7), but serum P4 was increased only in response to hCG. Largest follicle diameters on d 7 were less after GnRH and hCG, but total follicular volume on d 7 was reduced by GnRH, hCG, and CIDR, compared with that of controls. Volume of the original luteal structures was increased by hCG but tended to be reduced by CIDR and GnRH compared with luteal volume in controls. Total CL volume was increased by hCG, but reduced by CIDR, compared with CL volume of controls. Conception rates and pregnancy survival were assessed in response to the same treatments described in experiment 1: controls (n = 708), CIDR (n = 711), GnRH (n = 719), and hCG (n = 714). Tendencies for interactions of treatment x herd and treatment x lactation group were detected, but no 3-way interactions were found. Treatment with hCG increased conception rates in second-lactation cows. The CIDR tended to increase, and hCG increased, conception rates in 2 herds, whereas the CIDR decreased conception rates in 1 herd. Pregnancy survival was reduced by GnRH compared with that in controls. We concluded that GnRH and hCG effectively induced ovulation, and increased number of CL, but only increased serum P4 in hCG-treated cows. Further, treatment with the CIDR or hCG increased conception rates but only in some herds.

Physiological and practical effects of progesterone on reproduction in dairy cattle

“…However, circulating P4 remained lower, even after hCG treatment, in lactating cows compared with normally ovulating heifers. Eight studies that evaluated the effect of hCG on P4 concentrations from days 4 to 7 after AI in lactating dairy cows reported significant increases in circulating P4 concentrations after treatments with different doses of hCG: 3300 IU (Schmitt et al, 1996;Santos et al, 2001), 2500 IU (Stevenson et al, 2007b;Vasconcelos et al, 2011); 1500 IU (Walton et al, 1990;Hanlon et al, 2005; Kendall et al, 2009) or 1000 IU (Rajamahendran and Sianangama, 1992). Thus, treatment with hCG on day 5 after AI produces a consistent, fairly rapid (3 days delay) increase in circulating P4 in lactating dairy cows.…”

“…Of the 30 trials that we evaluated, the vast majority (25/30) showed a numeric improvement in fertility with P4 supplementation, although only six of these trials showed significance (P < 0.05). Only two (Stevenson et al, 2007b;Nascimento et al, 2013c) of these trials that found significance used >100 animals per comparison.…”

“…Of the 30 trials that we evaluated, the vast majority (25/30) showed a numeric improvement in fertility with P4 supplementation, although only six of these trials showed significance (P < 0.05). Only two (Stevenson et al, 2007b;Nascimento et al, 2013c) of these trials that found significance used >100 animals per comparison.The most extensive trials to increase P4 have been done by inducing formation of an accessory CL with hCG or GnRH treatment. When hCG or GnRH is administered on day 5 after AI, there is generally formation of an accessory CL and increased P4 during the mid-luteal phase (Fricke et al, 1993;Santos et al, 2001).…”

Exogenous hormonal manipulation to increase reproductive efficiency in dairy cows

“…In general, it is thought that stimulation of embryo development by an early rise in progesterone should benefit fertility (STRONGE et al, 2005;PARR et al, 2012), possibly because of advancing conceptus development. Nevertheless, fertility responses to exogenous progesterone seem to be greater when supplementation occurs before than after (STEVENSON et al, 2007) AI. In most studies with post-AI progesterone supplementation to lactating dairy cows no apparent attempt was made to mimic the normal rise in progesterone observed in heifers, which is greater and faster than that of cows ).…”

“…It is thought that inadequate progesterone concentrations during early development of the conceptus might be one of the reasons for reduced fertility observed in high-producing dairy cows (WILTBANK et al, 2011), in part because catabolism of steroids increases with increased feed intake associated with high production WILTBANK et al, 2011). In fact, supplemental progesterone after AI from an exogenous source (STEVENSON et al, 2007;WILTBANK et al, 2011) Timed AI protocols result in variable sizes of ovulatory follicles in dairy cows SANTOS et al, 2010). Induction of ovulation of small follicles resulted in reduced P/AI in beef (PERRY et al, 2005) and dairy cows , and increased risk of pregnancy loss (PERRY et al, 2005).…”