Progesterone-based strategies to induce ovulation in prepubertal Nellore heifers

Reproductive Performance of Prepubertal and Pubertal Heifers Submitted to timed Artificial Insemination Protocols

“…We hypothesized that these differences could be attributed to the breed, because Silveira et al [5] worked with crossbred (Bos indicus x Bos taurus) heifers. This hypothesis is supported by Rodrigues et al [11] who reported that heifers that were heavier at the beginning of the protocol, showed the highest percentages of estrous detection and the greatest number of ovulations. Studies by Carvalho et al [12] demonstrated that crossbred heifers had a larger dominant follicle (DF) on d8, a larger ovulatory follicle, and a higher DF growth rate compared with pure Bos indicus or Bos taurus heifers.…”

“…The PR percentages are based on the TAI, conventional AI, and natural breeding results. The protocols used for TAI in Bos indicus heifers using a longacting P4 intravaginal device followed by the administration of eCG or ECP after device removal have been previously reported by SáFilho, Marques and Baruselli [3], Claro Junior et al [1], Rodrigues et al [11], and Silveira et al [5]. These studies highlighted the importance of hormonal TAI protocols for this category of animal, with an emphasis on animal replacement.…”

“…This results indicates that exposure to the hormonal protocol for TAI, is primarily beneficial for prepubertal animals. It is plausible that ECP and eCG were more effective in prepubertal than in pubertal heifers, balancing the ovarian response at the beginning of the BS [11]. According to Rodrigues et al [11], isolated treatments with eCG and/or ECP after 12 days of previous exposure to intravaginal P4 in prepubertal heifers resulted in a higher induction of ovulation when compared to the control group, and the isolated use of ECP performed moderately and did not differ from other treatments.…”

“…It is plausible that ECP and eCG were more effective in prepubertal than in pubertal heifers, balancing the ovarian response at the beginning of the BS [11]. According to Rodrigues et al [11], isolated treatments with eCG and/or ECP after 12 days of previous exposure to intravaginal P4 in prepubertal heifers resulted in a higher induction of ovulation when compared to the control group, and the isolated use of ECP performed moderately and did not differ from other treatments. Table 1: Pregnancy rate (PR) after application of the hormonal protocol using estradiol cypionate and equine chorionic gonadotropin in Nellore heifers pretreated with an intravaginal device P4 (n=224).…”

“…Rodrigues et al [11] used eCG and ECP after intravaginal P4 in prepubertal Nellore heifers. They observed an increase in the rate of estrus detection and ovulation, thus improving the PR earlier in the BS.…”