Abstract

Milk progesterone profiles after artificial insemination (AI) were classified into the following four patterns:(1) normal type. Progesterone level (PL) rose promptly and remained high up to 2-3 days prior to estrus or day of pregnancy diagnosis (59%), (2) double peak type. PL rose first, then dropped temporarily in middiestrus, and rose again, forming double peaks (24%), (3) insufficiently rising type. PL rose, but remained below the lower limitof the normal range (11%), and (4) delayed type. PL rose 8-10days after AI (6%).Of 54 cows inseminated fifteen (28%) became pregnant, 29 returned to estrus 19-26days after AI, and ten maintained high PL's up to 30-60days after AI until they came into estrus. These 10 cows were considered to have had embryonic death. All the pregnant cows, but one, were associated with type 1. Of the 29 non-pregnant cows, eleven (38%) showed type 1, another eleven type 2, five (17%) type 3, and two (7%) type 4. Of the last 10 cows, seven (70%) showed type 1.It was suggested that the patterns of milk PL after AI rather than PL's themselves, might be associated with the fertility of cows.

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