176 Synchronisation of follicle wave emergence prior to superstimulation with purified FSH for ovum pickup affects blastocyst rate in pregnant Holstein heifers
L. Carrenho-Sala A , M. Fosado A , R. Sala A , E. Peralta A , D. Pereira B , D. Moreno B , J. Moreno C and A. Garcia-Guerra DA STgenetics, Kewaskum, WI, USA;
B STgenetics, DeForest, WI, USA;
C STgenetics, Navasota, TX, USA;
D Department of Animal Sciences, The Ohio State University, Columbus, OH, USA
Reproduction, Fertility and Development 32(2) 215-216 https://doi.org/10.1071/RDv32n2Ab176
Published: 2 December 2019
Abstract
The timing of initiation of superstimulatory treatments relative to follicle wave emergence has been shown to affect ovulatory response and in vivo embryo production. The significant increase of in vitro embryo production (IVP) and the possibility of using pregnant animals as oocyte donors has created the need to optimise superstimulatory treatments for IVP in pregnant cattle. Thus, the objective of the present study was to evaluate the effect of synchronisation of follicle wave emergence before superstimulation for ovum pickup (OPU) and IVP in pregnant heifers. Pregnant (47-62 days of gestation) Holstein heifers (n = 28) 19.5 ± 0.3 months of age were assigned in a completely randomised design to one of two groups: synchronisation of follicular wave emergence by dominant follicle removal (DFR; all follicles >6 mm) or untreated control (no DFR). Superstimulatory treatments were initiated 36 h after DFR or at random stages of the follicular wave in the no-DFR group and consisted of the administration of 160 mg of purified FSH (Folltropin-V, Vetoquinol) over four injections 12 h apart as follows: 48.0, 42.7, 37.3, and 32.0 mg. Ovum pickup was performed in all heifers 40 h after the last purified FSH injection. Heifers were subjected to OPU for oocyte recovery, and the number of follicles was determined. Recovered oocytes were processed in groups by treatment, and IVP was performed. Differences between treatment groups were evaluated using generalised linear mixed models. Results are presented in Table 1 and are expressed as means ± s.e.m. for data collected at the time of OPU or as proportions for embryo production results. The number of small follicles (<6 mm) at the time of OPU was greater in the no-DFR group than in the DFR group (P = 0.04). Conversely, there were no differences between treatments in the number of medium follicles (6-10 mm; P = 0.17), large follicles (>10 mm; P = 0.11), total follicles (P = 0.93), total number of recovered oocytes (P = 0.4), or number of viable oocytes (P = 0.53). The mean oocyte percentage recovery rate was not different between heifers in the DFR (53.6 ± 4.7%) and no-DFR (56.5 ± 4.7%) groups (P = 0.52). Both cleavage and blastocyst rate were greater (P < 0.008) in the DFR group than in the no-DFR group; as a result, the number of transferable embryos per animal was 5.6 in the DFR group and 2.8 in the no-DFR group. In summary, initiation of superstimulatory treatments at the time of follicle wave emergence improves cleavage and blastocyst rates, thus leading to greater embryo production.
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