Ovarian, hormonal, and reproductive events associated with synchronization of ovulation and timed appointment breeding of Bos indicus-influenced cattle using intravaginal progesterone, gonadotropin-releasing hormone, and prostaglandin F2α1

Abstract

The objectives of this study were to 1) compare cumulative pregnancy rates in a traditional management (TM) scheme with those using a synchronization of ovulation protocol (CO-Synch + CIDR) for timed AI (TAI) in Bos indicus-influenced cattle; 2) evaluate ovarian and hormonal events associated with CO-Synch + CIDR and CO-Synch without CIDR; and 3) determine estrual and ovulatory distributions in cattle synchronized with Select-Synch + CIDR. The CO-Synch + CIDR regimen included insertion of a controlled internal drug-releasing device (CIDR) and an injection of GnRH (GnRH-1) on d 0, removal of the CIDR and injection of PGF2alpha (PGF) on d 7, and injection of GnRH (GnRH-2) and TAI 48 h later. For Exp. 1, predominantly Brahman x Hereford (F1) and Brangus females (n = 335) were stratified by BCS, parity, and day postpartum (parous females) before random assignment to CO-Synch + CIDR or TM. To maximize the number of observations related to TAI conception rate (n = 266), an additional 96 females in which TM controls were not available for comparison also received CO-Synch + CIDR. Conception rates to TAI averaged 39 +/- 3% and were not affected by location, year, parity, AI sire, or AI technician. Cumulative pregnancy rates were greater (P < 0.05) at 30 and 60 d of the breeding season in CO-Synch + CIDR (74.1 and 95.9%) compared with TM (61.8 and 89.7%). In Exp. 2, postpartum Brahman x Hereford (F1) cows (n = 100) were stratified as in Exp. 1 and divided into 4 replicates of 25. Within each replicate, approximately one-half (12 to 13) received CO-Synch + CIDR, and the other half received CO-Synch only (no CIDR). No differences were observed between treatments, and the data were pooled. Percentages of cows ovulating to GnRH-1, developing a synchronized follicular wave, exhibiting luteal regression to PGF, and ovulating to GnRH-2 were 40 +/- 5, 60 +/- 5, 93 +/- 2, and 72 +/- 4%, respectively. In Exp. 3, primiparous Brahman x Hereford, (F1) heifers (n = 32) and pluriparous cows (n = 18) received the Select Synch + CIDR synchronization regimen (no GnRH-2 or TAI). Mean intervals from CIDR removal to estrus and ovulation, and from estrus to ovulation were 70 +/- 2.9, 99 +/- 2.8, and 29 +/- 2.2 h, respectively. These results indicate that the relatively low TAI conception rate observed with CO-Synch + CIDR in these studies was attributable primarily to failure of 40% of the cattle to develop a synchronized follicular wave after GnRH-1 and also to inappropriate timing of TAI/GnRH-2.

Endocrine factors and ovarian follicles are influenced by body condition and somatotropin in postpartum beef cows1,2

“…al., 1990; Diskin et al, 2003;Wettemann et al, 2003); however, minimal research exists on the relationship between BC, ST, and their interactions on follicular and endocrine function of beef cattle. Luteal status (anestrous or cyclic) of cows influences follicular responses to synchronization protocols (Stevenson et al, 2003;Saldarriaga et al, 2007). To achieve our objectives of evaluating BC and bST on follicular and endocrine function, a majority (78%) of cows in the current experiment were anestrous at the initiation of bST treatment.…”

Redução hormonal em protocolo Ovsynch para inseminação artificial em tempo fixo em fêmeas Nelore

“…As taxas de prenhez obtidas foram inferiores às citadas por Saldarriaga et al (2007) e Silva et al 2007, que obtiveram taxas de 39,00 % e 43,75%, respectivamente, para fêmeas zebuínas. Cavestany & Galina 2000, trabalhando com vacas de leite submetidas ao protocolo Ovsynch, obtiveram 28,10% de prenhez após única inseminação, sendo os resultados semelhantes ao do presente experimento.…”

Treatments to Optimize the Use of Artificial Insemination and Reproductive Efficiency in Beef Cattle under Tropical Environments

“…Protocols using GnRH and PGF2 α have afforded acceptable results in Bos taurus females (pregnancy rate >50% [41, 42]), but lower pregnancy rates have been reported for Bos indicus cows [24, 34, 43]. However, a commercial source of estradiol is not available for estrous cycle manipulation in many countries so other products (e.g., GnRH, LH, or hCG) have been used to induce ovulation of dominant follicles and follicular wave synchronization.…”