Abstract :
The aim of this study was to explore the possibility of increasing the ovulation rate of
Malpura, a non-prolific tropical breed of sheep by immunization against inhibin-based
peptide immunogens. Ewes were divided into three groups (n = 5 each) and actively
immunized against the synthetic peptides from the C [bI (1–29)-Tyr30] or N [bI-43-
Tyr152(153–167)Cys168] area of the bovine inhibin -subunit conjugated to ovalbumin or
against ovalbumin (control). Eachewe received a primary immunization of 400 gimmunogenand
3 boosters, eachof 200 gimmunogen at4-week intervals. Estruswas synchronized
using a double PGF2 injection schedule and laparoscopy was performed after each estrus
to determine the ovulation response. Immunization against both the peptides did not affect
the interval from PGF treatment to the onset of estrus, the duration of estrus and the number
of large unovulated follicles. In contrast to the complete absence of multiple ovulations
in the controls, all the ewes immunized against C or N peptides showed multiple ovulations
(range 2–7) in all the three estrous cycles evaluated, except for one ewe immunized
against the N peptide, which exhibited multiple ovulations in only 1 out of the 3 estrous
cycles. Compared to that of the controls (1.0±0.9, 1.0±0.0 and 0.6±0.2, respectively), the
mean ovulation ratewas higher (P < 0.01) in the ewes immunized against the C (4.8±1.02,
5.0±1.05 and 5.0±0.45, respectively) or against N (4.5±1.19, 2.5±0.87 and 2.7±0.75,
respectively, P < 0.05) peptide in estrous cycles numbers 1, 2 and 3. These results show that
active immunization against inhibin-based peptide immunogens is effective in increasing
ovulation rate in Malpura, a non-prolific breed of sheep and that it may be an alternative to
conventional superovulation regimes.
