Postpartum Estrus and Involution of the Uterus in an Experimental Herd of Holstein-Friesian Cows

Abstract

Summary A study of the intervals from parturition to involution of the uterus and from parturition to first heat was made respectively on 252 and 322 normal calvings in a Holstein-Friesian herd. The average interval to involution was 47 days, and that to first heat was 33 days. The difference in the involution interval between primiparous (42 days) and pluriparous (50 days) cows was highly significant, and significant differences were observed among seasons, being shortest in the summer and autumn. Cows calving during summer tended to come in heat earlier than those calving in the other seasons, whereas those calving during winter had the longest intervals from parturition to first heat. Examination of cows at the end of different intervals after calving showed that 95% or more of the cows in heat had their uteri involuted after an interval of 90 days. A slight association within the parity season groups (r = 0.147; P = 0.05) was found between intervals to first heat and to involution of the uterus. A study of 71 abnormal calvings indicated a little longer interval (5 days) to involution than for cows calving normally. The primiparous cows in this group also involuted earlier than pluriparous cows.