Physiological impact on fertility in cattle, with special emphasis on assessment of the reproductive function by progesterone assay
1981
Karg, H. (Technische Univ. Muenchen (Germany, F.R.). Lehrstuhl fuer Physiologie der Fortplanzung und Laktation)
Fertility is a multifactorial phenomenon where the converses (given in parentheses) of each of following events are major factors in infertility: establishment of cyclicity during puberty (acyclia); oestrus, insemination, ovulation (silent or unrecognized heat, false timing of AI, delayed ovulation); fertilization, development of the conceptus, shift to maternal conditions, pregnancy (embryonic death, abortion); parturition, delivery of the placenta, uterine involution (stillbirth, dystocia, retained membranes, uterine infections); and re-establishment of cyclicity post partum (acyclia, cysts, etc.). Modulating factors are breed, nutrition, housing conditions, season, age, milk yield, suckling, resting time post partum, regulatory disorders, infections, etc. The cause/effect situation for some of these influencing factors can be elucidated by hormone analysis. The progesterone assay especially has provided valuable screening concerning the fertility situation in herds in addition to farmers' observation and veterinary care. Detection of false timing of AI (which occurs on average 11% of cases; in problem herds up to 26%) by milk progesterone assay offers the possibility of improvement of management, and allows a correction factor to be applied to breeding statistics with the result of higher physiological relevance of breeding parameters. Using a two-sample regime (day of AI and 5-7 days later), anovulatory oestrus has been shown in the present study (with 1373 cows) to occur in 17% of cases. For assessment, of cycling, for instance in the evaluation of infertility events during the post-partum period, a two-sample per week regime is sufficient
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