Active immunization against inhibin improves superovulatory response to exogenous FSH in cattle

The effect of active immunization against inhibin on the response to superovulatory treatment by porcine FSH (pFSH) was investigated in cattle. Japanese black cows were sc injected with 1 mg of porcine inhibin alpha-subunit fragment (1-26) conjugated with rabbit serum albumin (inhibin-immunized group; n=14) or rabbit serum albumin alone (control group; n=12) in Freund's complete adjuvant. Booster injections (half the amount of the primary injection) were given 35 and 70 days after the primary injection. All cows were superovulated three times with pFSH. Three days after each injection of the antigen, a progesterone-releasing intravaginal device (CIDR-B) was inserted vaginally into all animals and left in place for 10 days. Forty-eight hours before CIDR-B removal, all animals were sc injected with 30 mg pFSH dissolved in 40% polyvinylpyrrolidone, and im injected with 750 microg of PGF2alpha at CIDR-B removal. Cows were artificially inseminated twice during estrus, and ova or embryos were collected 7 or 8 days after estrus. The number of corpora lutea, the number of ova or embryos and the number of transferable embryos in inhibin-immunized cows (12.1+/-1.2, 11.1+/-1.3 and 6.2+/-1.0, respectively) were significantly greater than those in the controls (8.2+/-1.0, 5.7+/-1.1 and 3.1+/-0.7, respectively). These results indicate that active immunization against inhibin enhanced ovarian response to the usual superovulatory treatment in cattle. Therefore, immunization against inhibin may be a useful approach for improving the response to superovulation in cattle.