153 Assessment of methods to synchronise follicle wave emergence in pregnant heifers
C. Hayden A , J. Motta A , N. Bello A , R. Sala B , V. Absalon-Medina B , P. Ross C , J. Moreno C and A. Garcia-Guerra AA Department of Animal Sciences, The Ohio State University, Columbus, OH, USA
B STgenetics, South Charleston, OH, USA
C STgenetics, Navasota, TX, USA
Reproduction, Fertility and Development 35(2) 204-205 https://doi.org/10.1071/RDv35n2Ab153
Published: 5 December 2022
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
Synchronisation of follicular development and initiation of follicle stimulating hormone treatment at follicle wave emergence (FWE) improves oocyte competence and in vitro embryo production in pregnant heifers. Follicle ablation, although effective for synchronisation of FWE, is time consuming and requires skilled personnel, highlighting the need for more practical methods. Thus, the objective of the present study was to evaluate the efficacy of various methods for synchronisation of FWE in pregnant heifers. Pregnant (60 days of gestation) Holstein heifers (n = 86) at 17.8 ± 2.2 months of age with moderate body condition score (3.2 ± 0.3) arranged in three weekly cohorts were randomly assigned to receive: gonadotrophin-releasing hormone (GnRH) (172 µg of gonadorelin acetate); human chorionic gonadotrophin (hCG) (3,300 IU); FA (ultrasound-guided follicular ablation of all follicles > 5 mm); or Control (4 mL of saline). Ultrasonography was performed for seven days after treatment to determine ovulation and emergence of a new follicular wave. Data were analysed using generalised linear mixed models with treatment as a fixed effect and cohort as a random effect. There was no evidence (P > 0.3) for an effect of treatment on largest follicle diameter nor total luteal tissue volume on Day 0. Ovulatory response was greater (P < 0.05) for heifers in the hCG (81.0%; 95% CI [58.0, 92.9]) group than for heifers in the GnRH (50.0% [28.8, 71.2]) group, whereas no ovulatory response was observed for heifers in the FA or Control groups. Heifers in the FA group had a shorter interval from treatment to FWE (34.8 ± 1.7 h) compared with heifers in the hCG (51.8 ± 5.4 h), GnRH (56.8 ± 5.4 h), and Control (61.4 ± 9.8 h) groups, though no evidence for any differences was apparent among the latter groups (P > 0.83). Furthermore, treatments differed (P < 0.001) in their variability of time interval from treatment to FWE, whereby FA-treated heifers had lesser variance (59 ± 19 h2) than heifers in the hCG and GnRH (560 ± 132 h2) groups, which, in turn, was less than that observed in heifers in the Control (1637 ± 579 h2) group. There was an effect of treatment (P = 0.003) on efficacy to synchronise FWE, defined as FWE within a predefined, treatment-specific 24 h period. Efficacy was greater (P < 0.05) in FA (97.6% [69.8, 99.9]) and hCG-treated (70.5% [48.3, 85.9]) heifers than Control heifers (27.5% [12.2, 50.9]), while there was marginal evidence (P = 0.06) for a difference in efficacy between heifers in the GnRH (69.1% [46.4, 85.2]) and Control groups. In addition, there was no evidence (P > 0.10) for a difference in efficacy between heifers in the FA, hCG, and GnRH groups. An effect (P = 0.0002) of treatment on Day 7 total luteal tissue volume was observed, whereby heifers in the hCG (8.6 ± 0.4 cm3) group had greater total luteal tissue volume than heifers in the FA (6.3 ± 0.4 cm3), GnRH (6.4 ± 0.4 cm3), and Control (6.2 ± 0.4 cm3) groups. In conclusion, there was no evidence for differences in FWE synchronisation efficacy between hCG, GnRH, and FA. Nevertheless, FA resulted in a shorter and less-variable interval from treatment to FWE, thus providing a more precise control of follicle development.
