Studies on the Endocrine and Environmental Factors Influencing Post Partum Acyclicity in Dairy Cows Based on Progesterone Profiles (Preliminary Results)

Abstract

The post partum period of 54 dairy cows was screened using progesterone determinations in fat free milk samples obtained every 2–3 days. Profiles were drawn of progesterone, milk yield and body weight change. On an average (^± s.d.) the cows had regained their early weight loss at 120 days post partum, the days open were 86^±27, and the period of acyclicity post partum was 33^±29 days. Cyclicity was resumed in 63% of the cows within 30 days and in 90% within 50 days post partum. First ovulation (after the first luteal phase) took place within 50 days post partum in 53% of the cows and within 70 days in 82%. A prolongation of the acyclic period was recorded together with a weight loss during the first 120 days post partum for some cows. Milk yield had no influence on the reproductive performance. The length of the post partum period of acyclicity was of importance for the onset of insemination, but had no decisive influence on the reproductive performance of the cows. Cows with an acyclic period of 30–60 days post partum could be inseminated and get pregnant within 90 days post partum.