Timing of prostaglandin F2α treatment in an estrogen-based protocol for timed artificial insemination or timed embryo transfer in lactating dairy cows

Abstract

Objectives were to investigate progesterone concentrations and fertility comparing 2 different intervals from PGF(2α) treatment and induced ovulation in an estrogen-based ovulation synchronization protocol for timed artificial insemination (TAI) or timed embryo transfer (TET) in lactating dairy cows. A total of 1,058 lactating Holstein cows [primiparous (n=371) and multiparous (n=687)], yielding 34.1 ± 0.33 kg of milk/d at various days in milk were randomly assigned to receive treatment with PGF(2α) on either d 7 or 8 of the following protocol: d 0: 2mg of estradiol benzoate + controlled internal drug release device; d 8: controlled internal drug release device removal + 1.0mg of estradiol cypionate; d 10: TAI or d 17: TET. Only cows with a corpus luteum at d 17 received an embryo and all cows received GnRH at TET. Pregnancy diagnoses were performed by detection (transrectal ultrasonography) of an embryo on d 28 or a fetus on d 60. Fertility [pregnancy per artificial insemination (P/AI) or pregnancy per embryo transfer (P/ET)] was affected by breeding technique (AI vs. ET) and time of PGF(2α) treatment (d 7 vs. 8) at the 28-d pregnancy diagnosis for TAI [32.9% (238) vs. 20.6% (168)] and TET cows [47% (243) vs. 40.7% (244)] and at the 60-d pregnancy diagnosis for TAI [30% (238) vs. 19.2% (168)] and TET cows [37.9% (243) vs. 33.5% (244)]. The progesterone (P4) concentration at d 10 altered fertility in TAI cows, with higher P/AI in cows with P4 concentration <0.1 ng/mL compared with cows with P4 concentration ≥ 0.1 ng/mL, and in ET cows, with higher P/ET in cows with P4 concentration <0.22 ng/mL compared with cows with P4 concentration ≥ 0.22 ng/mL. Prostaglandin F(2α) treatment at d 7 increased the percentage of cows with P4 <0.1 ng/mL on d 10 [39.4 (85) vs. 23.2 (54)]. Reducing the period between PGF(2α) and TAI from 72 to 48 h in dairy cows resulted in a clear reduction in fertility in cows bred by TAI and a subtle negative effect in cows that received TET. The earlier PGF(2α) treatment benefits are most likely mediated through gamete transport, fertilization, or early embryo development and a more subtle effect of earlier PGF(2α) treatment that may be mediated through changes in the uterine or hormonal environment that manifests itself after ET on d 7.

Physiological and practical effects of progesterone on reproduction in dairy cattle

“…Consistent with this idea, treatment with PGF2α one day earlier provided greater time for reduced P4 at the time of AI and Effects of P4 on reproduction in dairy cattle 75 improvements in fertility (Pereira et al, 2013). In this study, cows with P4 concentrations above 0.1 ng/ml near the time of AI had reduced fertility (Pereira et al, 2013). Thus, a small elevation in P4 near AI can reduce fertility.…”

“…An indication of improved fertility (P = 0.054) was observed at the 39 days pregnancy diagnosis with the 750 (247/ 544 = 45.4%) compared with the 500 (221/540 = 40.9%) µg dose of cloprostenol (Giordano et al, 2013b). Consistent with this idea, treatment with PGF2α one day earlier provided greater time for reduced P4 at the time of AI and improvements in fertility (Pereira et al, 2013). In this study, cows with P4 concentrations above 0.1 ng/ml near the time of AI had reduced fertility (Pereira et al, 2013).…”

“…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.…”

Prostaglandin F2α or estradiol benzoate to induce ovulation in timed artificially inseminated dairy cows

“…However, the intensive use of timed artificial insemination (TAI) protocols, observed in commercial herds in the last two decades, has apparently stabilized the fertility in high-yielding dairy cows. Recently, considerable research efforts have focused on developing efficient strategies to induce synchronized ovulation for TAI in dairy cattle (Pereira et al, 2013). The advent of protocols for ovulation synchronization, which enables artificial insemination at a pre-established time with adequate fertility, has become an important component of breeding management in multiple production systems (Bisinotto et al, 2014).…”