110 Pregnancy rate and embryo viability in response to chorionic gonadotrophins given for oestrus induction and gonadotrophin-releasing hormone 5 days after timed laparoscope-aided insemination of lactating and non-lactating goats
M. Calle A , L. Dawson A B , M. Rojas A and E. Loetz AA American Institute for Goat Research, Langston University, Langston, OK, USA;
B Animal Health Sciences, Oklahoma State University, Stillwater, OK, USA
Reproduction, Fertility and Development 33(2) 162-162 https://doi.org/10.1071/RDv33n2Ab110
Published: 8 January 2021
Abstract
Gonadotrophins are included in oestrous/ovulation synchronization (E/OS) regimens when breeding early in the transitional phase to promote follicular development. However, the time of use has been a matter of debate. Hence, the objective of this study was to determine whether equine and human chorionic gonadotrophins (eCG and hCG, respectively) given 24 h before or 24 h after concurrent removal of intravaginal progestagen (P4) and prostaglandin (PGF2α) delivery influences pregnancy rate (PR) and/or embryo viability (EV). Relatedly, the influence of gonadotrophin-releasing hormone (GnRH) 5 days post-breeding (dpb) on PR and/or EV was also considered. A prospective randomised control trial was conducted using lactating and non-lactating Alpine breed goats of different parity, average ± s.e. age, and bodyweight (3.7 ± 2.6), and (52.5 ± 7), respectively. Goats were time-bred at 48 h after P4 removal by laparoscopy (LAI; n = 75) or by natural service (NS; n = 29) during the early transitional breeding phase in mid-September through mid-December (corresponding to 12:12 h daylight/darkness). E/OS used an intravaginal device containing 300 mg of P4 for 12 ± 1d. At P4 removal, 2 mL of PGF2α was administered IM. Twenty-four hours before (E) or 24 h after (L) P4 removal, an IM dose of 1.5 mL containing 120 IU of eCG and 60 IU of hCG was given. A third control (C) group (n = 38) was not exposed to gonadotrophins. GnRH analogue was given (n = 51) 5 days after insemination, and the remaining goats (n = 53) received an IM dose of 2 mL of saline solution. PR was evaluated at 18 to 24 (dpb) by non-return to oestrus (NRE), at 30 dpb by pregnancy-specific protein B (PSPB), and at 40 dpb by ultrasound imaging (UI). EV was determined from the difference between pregnancy outcomes for NRE and PSPB, and PSPB and UI. Statistical analysis (JMP/SAS vs.11; SAS Institute Inc.) were obtained using logistic regression. All concomitant variables (i.e. parity, bodyweight, days of P4 exposure, and lactation were not influenced by PR or EV; P > 0.07). The overall PR was 71% for LAI and 69% for NS and, as shown in Table 1, was similar (P > 0.49) at all times (at 18 to 24, 30, and 40 dpb). Likewise, the breeding procedure did not influence the levels of EV at 30 or 40 dpb. E/OS protocol or the use of GnRH 5 dpb did not affect PR or EV at any of the time points evaluated.
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