Effect of gonadotropin releasing hormone at estrus on luteal function and fertility in crossbred cattle during heat stress
2000
Khan, B.
In this study crossbred dairy cows were in heat stress conditions continuously during the experimental period as indicated by the elevated temperature humidity indices. Administration of GnRH increased the progesterone concentrations in the treated animals as compared to control (P less than 0.05). The progesterone concentration in the GnRH treated pregnant and non-pregnant cows were higher than the saline control pregnant and non- pregnant cows (P0. 05) The first service pregnancy rate in GnRH treated group (40%) was significantly (P less than 0.05) higher then the control group (10%). Of the 40 cows 50% GnRH group and 40% saline group were identified as pregnant on day 21 based on high progesterone concentrations. When these cows were palpated for pregnancy confirmation after day 45 post-insemination, 40% and 10% in the GnRH and saline respectively were confirmed as pregnant. It was observed that more GnRH treated cows with prolonged high concentrations of progesterone were pregnant on 45 day after AI than control cows. The proportional loss of pregnancy between day 20 and palpation was 30% in control cows compared to 15% in GnRH treated cows. The 30% pregnancy loss in saline treated animals in the form of embryonic or fetal mortality can be attributed to high ambient temperature and relative humidity during summer. On the other hand, this effect was substantially reduced in the cows treated with GnRH. It is concluded that gonadotropins releasing hormone given 12 h before insemination may have enhanced luteal function in the form of increased progesterone concentrations and increased pregnancy rates by increasing embryonic survival during the period between day 21 and day 45. The finding of present study may open the area for investigation in buffaloes to overcome the seasonality in their breeding behaviour.
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