Reproductive effects of immunizing heifers against androstenedione and oestradiol-17

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Abstract
Heifers were treated with saline (group I, n = 10), keyhole limpet hemocyanin (KLH: group II, n= 10), androstenedione-KLH antigen (group III, n = 14), or estradiol-17.beta.-KLH antigen (group IV, n = 14). Booster injections were given to produce binding of > 10% at dilutions of 1:100 to 1:1000 (50% binding = 14.4 pg androstenedione and 9.5 pg estradiol). The heifers were mated and killed at .apprx. 46 days of gestation to establish ovulation rates, calf numbers, blood hormone relationships and ovarian morphology. Ovulation rate in animals immunized against androstenedione (group III) was significantly greater than in the other groups; 4 of the animals had double ovulations and 3 had twins. No significant differences were found between groups I, II and IV in relation to ovulation or pregnancy rate and animals immunized against estaradiol-17.beta. continued to cycle and become pregnant. Systemic progesterone, androstenedione and estrogen levels were generally increased in groups III and IV but the differences were no significant. No differences were detected between treatment groups in relation to CL [corpus luteum] weights, ovarian weights, follicle sizes or numbers. No binding of [3H]androstenedione or [3H]estradiol-17.beta. was detected in allantoic or amniotic fluids or fetal serum. [3H]estradiol in the follicular fluid sampled from the 2 largest follicles in the ovaries of each animal (group III, r = 0.59; group IV, r = 0.60; P < 0.05). The response of increased ovulation rate in cattle immunized against androstenedione should be further investigated to study follicular recruitment and increased productivity.