Effects of active immunization against inhibin and androstenedione, separately or together, on hormone profiles, ovarian follicle populations and ovulation rate in heifers

Abstract

It was postulated that the induction of twin ovulations in cattle may require a combination of two appropriate stimuli. The first putative requirement is an increase in the circulating FSH concentrations and/or a decrease in inhibin concentrations to induce the development of additional potentially ovulatory follicles. The second putative requirement is an increase in LH pulse frequency during the follicular phase of the cycle to enhance the stimulus for follicle maturation and ovulation. On the basis of studies reported in the literature, it was suggested that such stimuli may be provided by immunization against inhibin and against a steroid hormone such as androstenedione, respectively. This experiment was designed to determine the effects of immunization against androstenedione and inhibin, either separately or together on the endocrine status of heifers and on the associated patterns of ovarian follicle development and ovulation rate.

Effect of active immunization of heifers against inhibin on plasma FSH concentrations, ovarian follicular development and ovulation rate

“…Thus, despite some recent preliminary evidence to the contrary (Scanlon, Boland, Ireland & Martin, 1990;Rhind, Schemm & Schanbacher, 1991) the pre¬ sent data clearly show that active immunization against a synthetic fragment of inhibin can promote multiple follicular development and raise ovulation rate in heifers. The reason for the discrepancies between different studies in cattle remains obscure al¬ though the use of different inhibin-peptide conjugates may explain some of the variation in response.…”

“…(1990) nor Rhind et al (1991) confirmed that their peptide-immunized heifers produced antibodies which bound native inhibin. Further preliminary reports of increased follicular development and ovulation rate in inhibin-immunized beef heifers have recently appeared (Sunderland, Goulding, Kane et al 1991;Morris, McDermott & Sreenan, 1991) which support the findings of the present study.…”