Effect of reducing the period of follicle dominance in a timed artificial insemination protocol on reproduction of dairy cows

Abstract

Objectives were to determine the effect of reducing the period of follicle dominance in a timed artificial insemination (AI) protocol on pregnancy per AI (P/AI) in Holstein cows. In experiment 1, 165 cows received 2 injections of PGF(2alpha) at 36 and 50 d in milk (DIM). At 61 DIM, cows were assigned randomly to Cosynch 72 h (CoS72: d 61 GnRH, d 68 PGF(2alpha), d 71 GnRH) or to a 5-d Cosynch 72 h with 1 (5dCoS1: d 61 GnRH, d 66 PGF(2alpha), d 69 GnRH) or 2 injections of PGF(2alpha) (5dCoS2: d 61 GnRH, d 66 and 67 PGF(2alpha), d 69 GnRH). Blood was sampled at the first GnRH, first PGF(2alpha), and at the second GnRH of the protocols and assayed for progesterone. Ovulatory responses to GnRH were evaluated by ultrasonography. Cows were considered synchronized if they had concentrations of progesterone >or=1 ng/mL and <1 ng/mL on the days of the PGF(2alpha), and the second GnRH of the protocols, respectively, and if they ovulated within 48 h of the second GnRH injection. In experiment 2, 933 cows were assigned randomly to CoS72 or 5dCoS2. Blood was assayed for progesterone and ovaries were scanned as in experiment 1. Plasma on the days of the first PGF(2alpha) and final GnRH of the timed AI protocols was assayed for estradiol in 75 cows. Pregnancy was diagnosed on d 38 and 66 after AI. In experiment 1, the proportions of cows with corpora lutea (CL) regression on the day of AI differed and were 79.0, 59.1, and 95.7% for CoS72, 5dCoS1, and 5dCoS2, respectively. Cows that ovulated to the first GnRH of the Cosynch tended to have lesser CL regression than cows that did not ovulate (73.0 vs. 86.4%). Protocol synchronization differed between treatments and they were greater for CoS72 (69.4%) and 5dCoS2 (78.4%) than for 5dCoS1 (42.3%). In experiment 2, CL regression was lesser (91.5 vs. 96.3%) but detection of estrus at timed AI (30.9 vs. 23.6%) was greater for CoS72 than 5dCoS2, and cows in estrus had increased P/AI (46.2 vs. 31.9%). Cows in CoS72 ovulated a larger follicle and had greater concentrations of estradiol on the day of AI than cows in 5dCoS2, but protocol synchronization tended to increase in cows receiving the 5dCoS2. When all 933 cows were evaluated, P/AI was greater for 5dCoS2 than for CoS72 (37.9 vs. 30.9%). Similarly, when only cows with progesterone <1 ng/mL on the day of AI were evaluated, P/AI was greater for 5dCoS2 than for CoS72 (39.3 vs. 33.9%). Treatment with PGF(2alpha) on d 5 and 6 after GnRH resulted in increased luteolysis and allowed for reducing the interval from GnRH to timed AI, which increased P/AI. Reducing time of follicle dominance in timed AI protocols improves fertility of lactating dairy cows.

Exogenous hormonal manipulation to increase reproductive efficiency in dairy cows

“…Our observations of low fertility in cows that ovulated a persistent follicle are similar to results from numerous other studies (AHMAD et al, 1996;BLEACH;GLENCROSS;KNIGHT, 2004;CERRI et al, 2009;SANTOS et al, 2010) and are consistent with the idea that increasing the dominance period of follicles reduces fertility in the oocyte that is ovulated from the persistent follicle. This effect may be due to premature germinal vesicle breakdown due to excessive LH stimulation of the dominant follicle (AHMAD et al, 1994;REVAH;BUTLER, 1996).…”

“…Supplementing progesterone to mimic concentrations that typically are observed in dairy heifers, which were anticipated to length exposure of the conceptus and endometrium to concentrations compatible An additional hypothesis was that the beneficial effects of supplementing progesterone on fertility would be exacerbated in cows inseminated following timed AI. Although properly implemented timed AI protocols result in good to excellent embryo quality (CERRI et al, 2009b), synchronizing ovulation also results in variable size ovulatory follicles SANTOS et al, 2010), and inducing ovulation of small follicles reduces concentrations of progesterone during the subsequent diestrus (VASCONCELOS et al, 2001) and P/AI (PERRY et al, 2005;SOUZA et al, 2007). No interaction between supplemental progesterone and method of AI was observed, indicating that exogenous progesterone as CIDR4 and CIDR4+7 did not have a differential effect on pregnancy in cows inseminated either on estrus or following timed AI; however, the single insert on d 4 benefited pregnancy in cows inseminated following timed AI.…”

“…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).…”

Physiological and practical effects of progesterone on reproduction in dairy cattle

“…In summary, circulating P4 near AI, >0.1 ng/ml in a study using estradiol to induce ovulation (Pereira et al, 2013) or > 0.3 to 0.5 ng/ml in studies using GnRH to induce ovulation (Souza et al, 2007;Brusveen et al, 2009;Santos et al, 2010;Martins et al, 2011b;Ribeiro et al, 2012;Giordano et al, 2012b), is detrimental to fertility in dairy cattle, but the underlying physiological mechanisms that reduce fertility are not well understood. An additional PGF2α treatment in cows receiving Ovsynch and more precise detection of estrus may help to minimize the percentage of cows with elevated circulating P4 near AI.…”

“…Elevated P4 in vitro, also increased total α-inhibin production by the cumulus-oocyte complex, which may reduce embryo development after cleavage (Silva et al, 1999). Further, the reduced endometrial thickness that accompanies slight elevations in P4 (Souza et al, 2011) may indicate other major effects of P4 on the blood flow and functionality of the uterus and these changes could underlie the reduced embryo development.In summary, circulating P4 near AI, >0.1 ng/ml in a study using estradiol to induce ovulation (Pereira et al, 2013) or > 0.3 to 0.5 ng/ml in studies using GnRH to induce ovulation (Souza et al, 2007;Brusveen et al, 2009;Santos et al, 2010;Martins et al, 2011b;Ribeiro et al, 2012;Giordano et al, 2012b), is detrimental to fertility in dairy cattle, but the underlying physiological mechanisms that reduce fertility are not well understood. An additional PGF2α treatment in cows receiving Ovsynch and more precise detection of estrus may help to minimize the percentage of cows with elevated circulating P4 near AI.…”