Calf removal improves conception rates to the Ovsynch and CO-Synch protocols.

Abstract

Beef cows (n = 473) from two locations were stratified by breed, postpartum interval, age, and AI sire and were randomly allotted to one of four treatments for synchronization of ovulation. Ovulation synchronization protocols included the Ovsynch protocol with (n = 114) or without (n = 123) 48-h calf removal from d 7 to 9 (d 0 = 1st GnRH injection) or the CO-Synch protocol with (n = 119) or without (n = 117) 48-h calf removal from d 7 to 9. The Ovsynch protocol included administration of GnRH (100 microg; i.m.) on d 0, PGF2alpha (25 mg; i.m.) on d 7, GnRH (100 microg; i.m.) on d 9, and timed insemination on d 10. The CO-Synch protocol included administration of GnRH (100 microg; i.m.) on d 0, PGF2alpha (25 mg; i.m.) on d 7, and GnRH (100 microg; i.m.) with timed insemination on d 9. Blood samples were collected from all cows on d -10 and d 0 for analysis of serum progesterone. Cows with at least one serum progesterone concentration greater than 1 ng/mL were considered to be cyclic at the time of treatment. Conception rates of cows that received the CO-Synch + calf removal, Ovsynch + calf removal, CO-Synch, or Ovsynch protocol (63, 61, 54, and 52%, respectively) were not different (P = 0.50). Conception rates were not different (P = 0.80) among CO-Synch- and Ovsynch-treated cows; however, both estrual status and 48-h calf removal affected conception rates. Conception rates of cyclic cows (66%) were greater (P = 0.01) than those of anestrous cows (53%), regardless of which synchronization protocol was used. When data were pooled across synchronization protocol, conception rates of cows with 48-h calf removal (62%) were greater (P = 0.09) than conception rates of cows without calf removal (53%). The CO-Synch + calf removal protocol induces a fertile ovulation in cyclic and anestrous cows, requires handling cattle just three times, results in high conception rates from timed insemination, and should be a useful program for synchronization of ovulation in beef cows.

Strategies for rapid rebreeding of lactating ewes in the spring

“…The interval to first postpartum ovulation was reduced by an average of 23 days (P < 0.02) if cows suckled calves only once per day beginning at 30 days postpartum (Stagg et al, 1998). Effects of calf removal were most favorable when associated with timed inseminations (Kiser et al, 1980;Geary et al, 2001b) and if cows were in sub-optimal body condition (Kiser et al, 1980), but were less reliably observed in cows mated at estrus (Geary et al, 2001a). In sheep, reducing suckling intensity by separating spring-lambing ewes from their lambs during the daylight hours had no obvious positive effect on spring fertility (Whiteman et al, 1972), but that study did not include a control group.…”

Taxa de prenhez de vacas Nelore lactantes tratadas com progesterona associada à remoção temporária de bezerros ou aplicação de gonadotrofina coriônica eqüina

“…De forma similar, foi relatado que o efeito da RTB pode variar conforme a raça (Sanz et al, 2003) ou a idade das vacas (Geary et al, 2001;Santos & Santos, 2003).…”

“…Foram utilizadas vacas da raça Nelore e mestiças (Nelore × Red Angus) com 60 a 90 dias pós-parto e escore de condição corporal de 2,5 a 3,5 (1 = muito magra a 5 = muito gorda), segundo Lowman et al (1976). Os animais foram manejados extensivamente em pastagens de Brachiaria brizantha e receberam suplementação mineral ad libitum.…”

Synchronization of ovulation and fixed-time artificial insemination in beef cattle

“…The treatment protocol currently used in dairy cattle has been called Ovsynch (Pursley et al, 1995) in which GnRH is given 56 h after PGF and cows are inseminated 16 h later (Brusveen et al, 2008). CO-Synch protocols are more commonly used in beef cattle because cows are FTAI at the time of the second GnRH (Geary et al, 2001). Recent studies have shown that the first GnRH resulted in ovulation in 44% to 54% of dairy cows (Bello et al, 2006;Colazo et al, 2009), 56% of beef heifers (Martinez et al, 1999) and 60% of beef cows (Small et al, 2009), and the emergence of a new follicular wave was synchronized only when treatment caused ovulation (Martinez et al, 1999).…”

“…GnRH-based protocols have been used extensively for FTAI in dairy (Pursley et al, 1995) and beef cattle (Geary et al, 2001). The treatment consists of the administration of GnRH to induce LH release and ovulation of the dominant follicle, with emergence of a new follicular wave~1.5 to 2 days later.…”