Time of onset of post-partum luteal function and conception in dairy cows.

The following reproductive parameters were studied in 40 Icelandic dairy cows on 2 farms with free stall and tie stall housing: The time of onset of post-partum luteal activity; the time of first post-partum artificial insemination (AI); the time of conception; conception rate to first post-partum AI; the number of AI's per conception; length of gestation; and the number of days between 2 consecutive calvings. Milk for progesterone analysis was sampled 3 times a week from calving until first AI on farm 1, but every day for 90-100 days from calving on farm 2. In this study the average onset of luteal function was 21 days post-partum, the cows were inseminated 62 days and conceived 74 days post-partum. Conception rate to first AI was 71% and number of AI's per conception was 1.6. Significant differences were not found between the 2 farms. The reproductive performance of the cows in this study was greater than found in earlier studies of the Icelandic dairy cows and indicate that this animal has reproductive capabilities comparable to high producing foreign dairy cows.