Impacts of administering prostaglandin F2α analogue 24 h prior to progesterone insert removal on expression of estrus in beef females Academic Article uri icon

abstract

  • © 2019 Two experiments investigated the effects of administering prostaglandin (PG) F2α analogue 24 h prior to controlled internal drug release (CIDR) device removal in beef females assigned to GnRH-based synchronization protocols. In Exp. 1, 305 nulliparous heifers received 100 µg of GnRH and a CIDR containing 1.38 g of progesterone (P4) on day 0. Heifers were randomly assigned to receive 500-µg of cloprostenol on day 6 (PG6, n = 155) or day 7 (PG7, n = 150). The CIDR was removed on day 7, and heifers were monitored for estrus activity for 84 h after CIDR removal using detection patches. Heifers were artificially inseminated (AI) 12 h after being detected in estrus. Heifers that were not in estrus by 84 h after CIDR removal received GnRH (100 µg) and were inseminated 12 h later. Estrus expression was greater in PG6 vs. PG7 heifers at 48 h, but greater in PG7 vs. PG6 heifers at 60 h (P = 0.09) and 72 h (P < 0.01) after CIDR removal (treatment × time; P < 0.01). Cumulative estrus incidence was greater (P < 0.01) in PG6 vs. PG7 heifers by 60 h after CIDR removal (treatment × time; P < 0.01). No differences in pregnancy rates were observed (P = 0.43). In Exp. 2, 365 suckled multiparous cows received 100 µg of GnRH and a CIDR on day 0, and were assigned to treatments as in Exp. 1 (25 mg of dinoprost tromethamine; PG6, n = 147; PG7, n = 162). The CIDR was removed on day 7, and cows received 100 µg of GnRH and fixed-time AI on day 10. An estrus detection patch was applied to each cow on day 7, and estrus expression assessed at AI. Blood samples were collected on day 0 to determine the presence of a corpus luteum via plasma P4 (CL, P4 ≥ 1.0 ng/mL; NOCL, P4 < 1.0 ng/mL). Estrus expression was greater (P < 0.01) in PG6 vs. PG7 cows classified as CL, but similar (P = 0.96) within NOCL (treatment × CL status; P = 0.05). Pregnancy rates did not differ between treatments (P = 0.53), despite a 20% increase (P = 0.15) in PG6 vs. PG7 cows classified as CL. Therefore, PG6 increased the proportion of beef females that expressed estrus by 60 h after CIDR removal within a GnRH-based synchronization protocol, without substantially improving pregnancy rates to AI.

author list (cited authors)

  • Fontes, P., Cooke, R. F., Oosthuizen, N., Timlin, C. L., Dias, N. W., Currin, J. F., ... Mercadante, V.

citation count

  • 2

publication date

  • August 2019