The Thai Journal of Veterinary Medicine


In order to determine the optimal time for AI, we have measured the serum reproductive hormones (progesterone, estradiol and LH) from 89 dairy cows by radioimmunoassay and mouse Leydig cell LH bioassay. Fifteen ml. of jugular blood sample was obtained on Day of AI and Day 7, 14, 21 after AI. Rectal palpation for pregnancy detection was performed by 45 days after AI, and it was found that 23 cows were pregnant. The progesterone levels were not significantly different between both groups by day of AI but it was markedly high from Day 14 through Day 21 in pregnant cow. In contrast, its levels in non-pregnant group declined gradually from Day 14 to 21. On the day of AI, concentration of serum E was lower in pregnant cows than in non-pregnant group (7.17 vs 9.52 pg/ml) whereas the opposite direction was observed in LH levels (116.78 vs 94.43 ng/ml). The present study demonstrated that serum concentrations of estradiol and LH could be used as the indicators to adjust the optimal time for AI and the progesterone levels could be used to detect pregnancy by Day 21.

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