A Study of Ovulations in Six Families of Holstein-Friesians

Abstract

The incidence of multiple ovulations in the Emmons Blaine, Jr. herd of experimental Holstein cows was found to be 13.10 per cent, while the incidence of twinning was 1.92 per cent, a highly significant difference. The incidence of multiple ovulations was not significantly influenced by reproductive period, family, or length of time after parturition. There was a significant monthly variation in frequency of multiple ovulation in the first reproductive period and the monthly variation in the second period approached significance, being high in May and low in September in both cases. A highly significant tendency for multiple ovulations to follow in sequence was found. Significantly higher fertility was noted when cows were bred at an estrus from which only a single corpus luteum was formed as compared to an estrus from which two or more corpora lutea were formed. The incidence of “quiet” ovulations (44.3 per cent) was significantly higher during the first 60 days after parturition than during the period 61 to 308 days post-partum. During this latter period their incidence was still sufficiently high (11.0 per cent) to constitute an important problem to the breeder. Of the ovulations 56.5 per cent were from the right ovary. Studies of family and parity failed to show any significant deviations from this ratio. No apparent tendency was found for cows to have a systematic sequence of ovulations from one ovary or the other. © 1952, American Dairy Science Association. All rights reserved.