| Summary: | An experiment was conducted to investigate the effect of different doses of follicle stimulating hormone (FSH) usedin a superovulation program on numbers of corpora lutea, total ova/embryos and transferable embryos in Kamphaeng Saenbeef cattle. Cyclic cows (n=3) and heifers (n=3) of Kamphaeng Saen beef breed were assigned to two levels of FSH (200 and250 mg. NIH-FSH-P1) in Crossover Design by which two changes over treatments were studied over two periods in allanimals. Cows and heifers were estrous synchronized by Cloprostenol (500 μg). Estrus detection was performed by teaserbull (Day 0 = day of the onset of standing estrus). On day 9 after the onset of standing estrus, all animals were treated withFSH twice daily in decreasing doses over 4 days. On day 3 of FSH injection, each animal was treated with Cloprostenol (500μg). At the first standing estrus, all animals were artificially inseminated three times at 12 h intervals. Two straws of frozenthawedsemen of Kamphaeng Saen bull were used per insemination. All animals were treated with gonadotropin releasinghormone (10 μg of Buserelin) at first insemination. Numbers of corpora lutea were determined by rectal palpation and embryoswere flushed seven days after the onset of standing estrus and classified according to the development stage and quality.The results showed that numbers of corpora lutea, percentages of total ova/embryos and percentages of transferable embryoswere not significantly different (P>0.05) between treatments (FSH: 200 versus 250 mg) in either cows or heifers.
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