Impact of progesterone and estradiol treatment before the onset of the breeding period on reproductive performance of Bos indicus beef heifers

Abstract

The present aimed to develop a hormonal therapy based on the insertion of a progesterone (P4) insert (PI) during 10 d plus an estradiol injection (E2) at PI removal before the onset of breeding of beef heifers. In Exp. 1, the plasma P4 profile of prepubertal heifers showed that the insertion of a PI or 24 d previously used P4 insert (UPI) sustained plasma P4 above 1 ng/mL for at least the first 7 d of the treatment. In Exp. 2 there was no positive effect of additional estradiol benzoate (EB) administered at the insertion of UPI on the proportion of heifers with a corpus luteum (CL/Treated) 30 d after UPI removal [UPI + EB = 85.3%(a) (n = 134); EB + UPI + EB = 80.8%(a) (n = 125)]; however, both were greater (P < 0.0001) than the Control group [60.3%(b) (n = 129)]. In Exp. 3, a positive effect (P=0.01) of UPI treatment and both E2 supplementations [EB and estradiol cypionate (EC); P = 0.10] at the UPI removal was observed on CL/Treated [Control = 42.5%(b) (n = 94); UPI = 58.5%(a) (n= 130); UPI + EB = 64.0%(a) (n = 128); UPI + EC = 67.2%(a) (n = 128)]. However, greater pregnancy per treated heifer (P/Treated) following artificial insemination (AI) upon estrus detection was achieved when EC was applied [Control = 20.2%(b); UPI = 29.2%(ab); UPI + EB = 26.6%(b); UPI + EC = 36.7%(a)]. In Exp. 4, the treatment prior to the timed AI (TAI) tended to improve pregnancy per TAI [P/AI; Control 43.6% (n = 298) vs. UPI+EC 51.9% (n = 342); P = 0.08], but increased P/Treated [26.5% vs. 43.3%; P < 0.001]. Thus, UPI + EC treatment were efficient in increasing the CL/Treated, tended to improve the P/AI and consequently enhanced P/Treated of zebu beef heifers.

Injectable progesterone in timed artificial insemination programs in beef cows

“…In this context, the synchronic control of wave emergence, dominant follicle growth and ovulation are the main requirements of a hormonal protocol that allow to AI or embryo transfer at a fixed time (Bo et al, 2003;Baruselli et al, 2004;Carvalho et al, 2008;Sá Filho et al, 2013;Sá Filho et al, 2015). Additionally, this pharmacological strategy optimizes the use of females as well as increases the pregnancy rate and reduces the costs of reproductive programs (Marinho et al, 2012).…”

Corpus luteum dynamics after ovulation induction with or without previous exposure to progesterone in prepubertal Nellore heifers

“…Consequently, regression of the CL is not stimulated before the physiological time [25]. According to S a Filho et al [28,29] and Pfeifer et al [22], previous exposure to P4 prolongs persistence of the CL and improves pregnancy/artificial insemination rates.…”

Fatores relacionados ao desenvolvimento reprodutivo em novilhas Nelore: Revisão

“…Nesse sentido Sá Filho et al (2015) dosaram a concentração circulante de P4 em novilhas Nelore pré-púberes onde avaliaram a eficácia da utilização de CIDR ® s novos, ou usados previamente utilizado por 3 vezes durante 8 dias, denominados de CIDR ® 4 (24 dias de uso prévio) implantados intravaginalmente por 10 dias, em relação ao grupo sem implante intravaginal de liberação lenta de P4 (Controle). Foi verificado que ambos os dispositivos foram capazes de PUBVET v.12, n.5, a82, p.1-10, Mai., 2018…”