FR 24. Effect of bull exposure on corpus luteum function and ovarian activity in prepuberal Brahman heifers
The objectives of this study were to determine if the effect of bull exposure would affect age at puberty, corpus luteum function and ovarian activity in prepuberal Brahman heifers. Forty Brahman heifers were alloted randomly to the following treatments: 1) heifers exposed to mature bulls (T1; n=20) or 2) heifers isolated from bulls or control group (T2; n=20). Heifers were monitored by ultrasound weekly and numbers of small (3-6 mm) and large (7-10 mm) follicles present at each session were determined. Similarly, blood samples were collected at weekly intervals for 34 weeks to determine progesterone (P4) concentrations and onset of ovarian luteal function. Age of puberty did not differ (P<.05) between treatments. However, prepuberal Brahman heifers of T1 had greater (P<.004) accumulated P4 during the 34 week period than T2 heifers, this effect was more pronounced after a 4 month exposure . Likewise, heifers in T1 accumulated more small (4.6; P<.001) and large (2.1; P<.007) follicles than T2 heifers. Results of this experiment indicate that presence of a mature bull does increase luteal and follicular function in prepuberal Brahman heifers.