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LH and Prolactin in Blood Serum from Estrus to Ovulation in Holstein Heifers¹

Michigan State University, East Lansing, Michigan 48823

Abstract

Blood samples were taken from five Holstein heifers at 2- to 6-hr. intervals from 4 days before estrus until ovulation to relate levels of LH and prolactin to behavioral and ovarian changes. Serum LH began a nonsignificant continuous rise 5 days before estrus, concluded by a burst (P<.01) of LH 19 times greater than the baseline; the peak preceded onset of standing heat by 3 hours. Serum LH was elevated for 6 to 8 hr. and ovulation occurred 32 hr. after the LH peak. Within 4 to 6 hr. after the peak, serum LH returned to pre-estrual levels and remained with little variance at that baseline for the remainder of the study (3 days). Prolactin, more variable than LH within heifers, was elevated (P.08) during estrus and declined during the 2 days following estrus.

¹ Michigan Agricultural Experiment Station Journal Article No. 5407. Drs. David Morrow, Lee Edwards and Richard Koritansky performed the rectal palpations to determine ovulation. Dr. L. E. Reichert supplied the highly purified bovine LH (LER-1072-2) and Dr. G. D. Niswender provided the anti-bovine LH serum for LH radioimmunoassay.

² Present address: Department of Animal Sciences, Oregon State University, Corvallis 97331.

³ Animal Reproduction Laboratory, Dairy Department.