Abstract:

【Objective】 This study aimed to increase embryo production in superovulated heifers by immunization against inhibin. 【Method】 Immunization procedures consisted of primary injection (i.m.) of 1mg recombinant inhibin? α-subunit protein in 1 ml mineral oil adjuvant, and two booster immunizations with 0.5 mg inhibin protein at 28 day intervals. Ten days after the 2nd booster immunization, all animals were superovulated with exogenous FSH, inseminated either with conventional semen (Experiment 1) or sex sorted female semen (Experiment 2). The embryos were collected and evaluated 7 days after insemination.【Result】 Immunization significantly increased blood antibody titres against recombinant inhibin α subunit protein (P＜0.01). In experiment 1, the immunized heifers produced more embryos and ova than the control heifers (15.8±2.8 vs 8.3±1.5, P＜0.05), and non-significantly more number of transferable embryos (9.6±3.1 vs 5.8±1.6, P＞0.05). In experiment 2, inhibin immunized heifers initiated estrus earlier after FSH treatment, and had higher plasma progesterone concentrations on the day of embryo collection. In the inhibin immunized heifers, the total number of embryo/ova were (15.4±1.9), significantly higher than that (9.1±1.2) of control heifers (P＜0.05), while the total number of transferable embryo in the former (5.7±0.7) was also higher than in the latter group (3.1±0.5) (P＜0.05). Within the transferable embryos, there was (3.8±1.0) or 58% grade 1 embryos in the immunized heifers, higher than the 0.6±0.2 or 19.8% in control heifers (P＜0.05). 【Conclusion】 These results indicated that immunization against inhibin increased heifer response to superovulation, and led to higher yield of total and transferable embryos, as well as increased the embryo quality.

Key words: holstein heifers')">holstein heifers, inhibin immunization, superovulation, embryo yield