Özet:

The changes and relationships between plasma progesterone and vaginal resistance values after cloprostenol injections were determined and also the luteolysis process was monitored by plasma progesterone Ievels in heifers. The study was conducted on randomly selected 22 Brown Swiss heifers. İntramuscular injections of 500 mcg cloprostenol were applied in heifers without any effort to detect of their cyclic phases. Estrous heifers were detected by clinical inspections after treatment. On the day of injection and following four days jugular blood samples and vaginal resistance records were taken daily. Seventeen (77 % ) of 22 heifers injected with cloprostenol displayed estrus but five (23 %) have failed. All of these five animals have showed estrus symptoms after second cloprostenol injections and it has been concluded that they were in metestrus stage of the cycle at the time of fırst treatment. In these heifers vaginal resistance values were correlated -0.40 with plasma progesterone levels. Eight heifers having lower plasma progesterone levels than 1 ng/ml on injection day, that come into estrus after treatrnent, were deduced that they were in proestrus stage of the cycle on the day of treatrnent and showed estrus symptoms as a result of their normal follicular development. In this heifers vaginal resistance values were correlated 0.50 with plasma progesterone levels In nine heifers having higher plasma progesterone levels than 1 ng/ml at injection day and five heifers receiving second cloprostenol injections, plasma progesterone have dropped promptly and remained lower than 1 ng/ml for four days. In these groups of heifers vaginal resistance values were correlated 0.93 and 0.94 with plasma progesterone levels, respectively. It was concluded that luteolysis process can be monitored by vaginal resistance values after prostaglandin treatments in heifers having higher progesterone levels than 1 ng/ml.

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