Medycyna Wet. 64 (4b), 525-527, 2008

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Pilawski W., Siemieniuch M. J., Skarżyński D. J.
Influence of estrus synchronization and superovulation on corpus luteum functioning in cattle. Does hormonal manipulation always provide desirable effects?
The main function of the corpus luteum (CL) is progesterone (P4) production, a factor which regulates the estrous cycle and provides proper embryo and fetus development, the hormone that determines the efficiency of reproduction. Estrus synchronization is one of the basal methods applied in reproductive biotechnics. However, pharmacological manipulation of the estrous cycle may cause various CL dysfunctions, including abnormal P4 synthesis after superovulation or synchronization of the cycle. In the authors studies the influence of different methods of estrous synchronization (injection of PGF2a analogues: dinoprost, cloprostenol and luprositiol; or gestagens treatment: norgestomet) on CL sensitivity to luteotropic factors (LH and PGE2) was investigated. With the use of PGF2a analogues the lower action of luteotropic factors on the CL function was demonstrated in the CL after estrus synchronization. Physiological CL sensitivity to the stimulation was observed in CL from the cows with norgestomet-synchronized cycles. The only effects of dinoprost on CL functioning in vitro were conferrable and similar to the natural PGF2a action. Other PGF2a analogues much more powerfully and differently influenced the cells/tissues of the bovine reproductive tract compared to natural PGF2a action. Lower P4 production in the CL after hormonal manipulation may cause insufficient protection of the embryo by the CL products during the first critical pregnancy period and lead to the early termination of pregnancy.
Keywords: prostaglandin F2a, corpus luteum, estrous synchronization, cow