Effectiveness of GnRH plus prostaglandin F2alpha for estrus synchronization in cattle of Bos indicus breeding.

Abstract

Postpartum and lactating crossbred cows containing a percentage of Bos indicus breeding at three locations were studied to determine the efficacy of GnRH + PGF2alpha combinations for synchronization of estrus and(or) ovulation. Cows were equally distributed to each of three treatments by body condition score at the start of the experiment (d 0). All cows received 100 microg of GnRH on d 0 and 25 mg of PGF2alpha 7 d later. The three insemination protocols included 1) AI 12 h after exhibiting estrus during d 7 to 12 of the experiment (Select-Synch; n = 197); 2) timed-AI + 100 microg of GnRH on d 9 of the experiment (CO-Synch; n = 193); 3) AI 12 h after exhibiting estrus during d 7 to 10 of the experiment. Cows not exhibiting estrus by d 10 were timed-AI and injected with 100 microg of GnRH on d 10 of the experiment (Hybrid-Synch; n = 200). The percentage of cows exhibiting estrus during d 7 to 12 of the experiment was lower (P < 0.05) for CO-Synch (17.6%) cows than for Select-Synch or Hybrid-Synch (45.2 and 33.0%, respectively) cows, which did not differ (P > 0.05). For the Select-Synch and Hybrid-Synch cows that exhibited estrus during d 7 to 10 of the experiment and were artificially inseminated, conception rates were similar across treatments (50.5%). Pregnancy rates were greater (P < 0.01) for CO-Synch and Hybrid-Synch (31.0 and 35.5%, respectively) cows than for Select-Synch (20.8%) cows. A greater (P < 0.01) percentage of cycling cows became pregnant (34.5%) than noncycling cows (25.9%) across all treatments. The CO-Synch and Hybrid-Synch synchronization protocols resulted in greater pregnancy rates compared with the Select-Synch protocol in postpartum and lactating crossbred cows containing a percentage of Bos indicus breeding.

Estrous behavior and initiation of estrous cycles in postpartum Brahman-influenced cows after treatment with progesterone and prostaglandin F2α1,2

“…Cyclic cows had greater pregnancy rates than anestrous cows in the current study. Several studies have reported the positive effect of the presence of luteal activity at the initiation of the breeding season on pregnancy rate in both beef (Lemaster et al, 2001;Lucy et al, 2001) and dairy (Rhodes et al, 2003;Galvã o et al, 2004) cattle.…”

“…Recently, a controlled internal drug-releasing (CIDR) device containing progesterone (P 4 ) along with PGF 2α has effectively synchronized estrus in beef cows and heifers and reduced the interval to estrus in anestrous suckled beef cows (Lucy et al, 2001). Estrous synchronization with P 4 has been conducted with Brahman heifers with CIDR-PGF 2α (Lemaster et al, 1999) and Brahman-influenced cows with CIDR-GnRH (Lemaster et al, 2001), norgestomet-PGF 2α (Williams et al, 2002), or melengestrol acetate (MGA)-GnRH-PGF 2α (Hiers et al, 2003). Effects of a CIDR-PGF 2α treatment on estrous characteristics of Brahman-influenced cows are lacking.…”

Sincronização da ovulação com dispositivo intravaginal de progesterona (CIDR®) em novilhas Bos indicus, Bos indicus x Bos taurus e Bos taurus

“…taurus (RANDEL, 1984;SEGERSON et al, 1984) A eficiência máxima de um sistema de sincronização do cio/ovulação em bovinos é determinada pela capacidade de induzir a ovulação em tempo previsível, de maneira que um grande número de fêmeas possam ser inseminadas sem a necessidade de detecção de cio (LEMASTER et al, 2001). Em geral, a baixa fertilidade após a IATF tem sido atribuída à falta de sincronia do cio/ovulação ou à ovulação de um oócito envelhecido em conseqüência do período prolongado de crescimento folicular, tipicamente associado com os folículos persistentes (AHMAD et al, 1995 …”

Use of Technology in Controlling Estrus in Cattle

“…73,74 However, Williams et al 75 developed a breeding protocol (GnRH plus PGF 2α on day of CIDR insertion and CIDR inserted for 5 days, PGF 2α on day of CIDR removal, GnRH and TAI at 66 hours with pregnancy rates of greater than 50% consistently) in cattle with Bos indicus genetics. Commercial progestogen products are now available.…”