Effect of semen source and dose of FSH on superovulatory response and embryo production in Holstein heifers
Anim Reprod, vol.4, n3, p.70-76, 2007
This study evaluated fertilization rate and embryo quality in superstimulated Holstein heifers artificially inseminated with pooled semen from four high fertility bulls or commercial semen from one of four selected sires (not pooled). It also evaluated the superovulatory response to two different doses of FSH. Twenty heifers underwent two superstimulatory treatments in a crossover design. On Day 0, all heifers received an intravaginal progesterone device (CIDR). On Day 1, heifers were treated with estradiol benzoate (3 mg). Starting on Day 6, heifers were treated with one of two different amounts of FSH using progressively decreasing doses. Prostaglandin F2α was given 12 h before CIDR removal, and GnRH (100 μg) was given 36 h after CIDR removal. Heifers received a single AI 12 h after the GnRH injection. Fertilization rate (83% vs. 77%, P = 0.35) and percentage of transferable embryos (52% vs. 45%, P = 0.55) recovered per flush for pooled highfertility vs. commercial semen did not differ. The higher dose of FSH stimulated growth of more (P < 0.01) follicles > 8 mm in diameter per heifer (16.8 ± 1.6 vs. 12.9 ± 1.2). However, number (2.3 ± 0.5 vs. 3.3 ± 0.8, P = 0.21) and percentage (38.2 ± 8.9 vs. 59.8 ± 10.3, P = 0.28) of transferable embryos did not differ between the high and low FSH group. In addition, lowering the dose of FSH decreased (P = 0.04) the number of unfertilized ova (1.6 ± 0.5 vs 0.6 ± 0.2). In conclusion, decreasing FSH to 50% (200 mg) of the recommended dose (400 mg) did not reduce the number or percentage of transferable embryos. Moreover, number of unfertilized ova appeared to depend as much on FSH dose as semen quality, with increasing FSH dose decreasing fertilization efficiency and commercial semen from individual sires producing an acceptable fertilization rate in superstimulated heifers.
dose of FSH; pooled semen; fertility