146 Single injection of follicle-stimulating hormone before ovum pickup in lactating Holstein donors: Oocyte recovery and embryo production

Lactating donor cows frequently have decreased oocyte quality, lower fertilization rates, and impaired early embryonic development due to their lactational metabolic challenges. Synchronization and stimulation of follicular growth before ovum pickup (OPU) has been used to improve oocyte quality and consequently, embryo production. The objective of this study was to evaluate the effects of a single injection of FSH before OPU on oocyte recovery and embryo production in lactating Holstein donors. During June and July 2020, 22 lactating Holstein donors (open, 40 to 90 DIM, producing >90 lbs of milk) from Ruann Dairy (Riverdale, CA) were randomly assigned to one of two treatments (crossover design). Donors did not receive any injections before OPU when assigned to the No FSH treatment. Treatment 1×FSH consisted of a single intramuscular (IM) injection of 140 mg of FSH (Folltropin®, Vetoquinol) 36 h after gonadotrophin-releasing hormone (GnRH; Fertagyl, Merck®, 129 µg, IM). The FSH consisted of a 3.5-mL IM injection of 400 mg of FSH diluted in 10 mL of 0.5% hyaluronan (HA). OPU was performed 48 to 52 h after FSH. All donors received both treatments on a 14-day interval. The recovered oocytes were fertilized with the same sexed female-sorted semen in both rounds (3 different sires were used). OPU, oocyte classification, IVM, IVF, and culture (IVC) were performed as described by Demetrio et al. (2020 Anim. Reprod. 17, e20200053). All oocytes went into IVM, except for degenerated occytes. The number of 4-cell (or more) embryos on Day 3 of IVC divided by the number of oocytes in IVC after IVF is defined as the cleavage rate. The number of blastocysts (early to hatched) on Day 7 of IVP divided by the number of oocytes in IVC after IVF is defined as the blastocyst rate. Poisson-normal (count data) and Logistic-normal (proportion data) models were used to analyse the data. Treatment, donor (random effect), and sire were included in the models. The results are summarised in Table 1. Oocyte recovery and embryo production were highly donor dependent. There were no differences in the number of recovered oocytes among treatments. Stimulation of the follicular growth before OPU with one single injection of FSH diluted in 0.5% HA 36 h after GnRH improved oocyte quality, cleavage rates, blastocyst rates, embryo quality, and the total number of embryos per OPU in lactating Holstein donors. Table 1. Oocyte recovery, cleavage rate, and embryo production results Treatment OPU Oocytes per donor Grade 1 and 2 oocytes Cleavage rate (%) Blastocyst rate (%) Total embryos per OPU Grade 1 embryos per OPU No FSH 22 18.2 30a 69a 22a 3.4a 1.6a 1 × FSH 22 17.5 34b 77b 34b 5.3b 3.3b a,bValues with different superscripts in the same column differ (at least P < 0.05).