[Relation between cervical mucus sperm toxicity and pregnancy in cows].

Cervical secretion was collected from 99 dairy cows of the Black Pied Lowland breed at an age of 24 to 109 months with a minimum performance of 4000 kg of milk annually in spontaneous oestrus 42 days post partum at the minimum. It was demonstrated by the radioimmunological determination of progesterone in skim milk that from all the breeding cows (n = 99) the oestral secretion was collected during an optimum insemination time (x = 0.19 ng.ml-1 progesterone). Of the statistical set of 99 cows, 55 (i.e. 56.57%) got in calf and 43 (i.e. 43.43%) remained barren. As found, the conception results were not influenced by the rank of the insemination after parturition and the conception capacity of the cows was not influenced by the length of time from parturition to the respective inseminations. It was demonstrated in our investigation that the conception capacity of the cows increases as the time of sperm survival prolongs in the cervical secretion in vitro. The highest conception capacity (80%) was recorded in the cows whose cervical secretion was free of spermiotoxic action. In such cases the motility of the spermatozoa in the oestral mucus was maintained at a temperature of 38 degrees C for longer than 300 minutes. On the other hand, it was demonstrated that the conception capacity of the cows declines with shortening time of sperm survival in the cervical mucus.