OVARIAN ACTIVITY IN GILTS INCLUDING SOME CHARACTERISTICS OF A NATIVE BREED

Follicular development and ovulation result from a coordinated change in the balance of gonadotropins (LH, FSH) and steroids (progesterone, estradiol) during the estrous cycle. Emergence of ovulatory follicles is associated with decreased secretion of progesterone in the absence of significant change of LH concentration. Unlike what occurs in cattl e, there is only one wave of follicular development during the porcine estrous cycle. The recruitment of these follicles is initiated by the postovulatory FSH surge. Preovulatory follicles grow and differentiat e in an environment of declined FSH concentrations. Based on this phys iological conditions there are two possible strategies to influence fo llicular development. Compared to the number of follicles destined to ovulate (about 12-18/gilt) the potential of recruited follicles is mor e than 2- to 3-fold higher. The first strategy includes the applicatio n of gonadotropins, i.e. PMSG, which has both a definite FSH and a bal anced LH activity, during the follicular phase to influence the number of selected follicles. The second strategy comprises the application of porcine FSH during the early luteal phase to support the postovulat ory FSH surge to increase follicle recruitment. Aboriginal and endange red swine breeds with different genetic, commercial or national value have been more and more in the focus of interest. Mangalica is a value nativ pig breed adapted to extensive climate and housing conditions i n Hungary. Compared to modem breeds, Mangalica has a poor reproductive ability. Fecundity in different swine breeds may have its origin in o varian reactivity. To propagate the very small population by means of biotechnical methods, the ovarian reactivity was analyzed after estrou s synchronization with Regumate(R) and stimulation with different trea tments of PMSG. The application of 1000 and 1250 IU PMSG resulted in a significant higher number of ovulation (24.2+/-2.5 and 21.0+/-2.9, p= 0.01) compared to 750 IU PMSG and to untreated sows (13.7+/-3.1 and 11 .5+/-2.1, respectively). Embryos recovered at the blastocyst stage wer e successful used in a embryo transfer program. Unsufficient ovarian r eactivity seems not to be the reason of low fertility in Mangalica.