Comparison of Follicular and Oocyte Development and Reproductive Hormone Secretion during the Ovulatory Period in Hungarian Native Breed, Mangalica, and Landrace Gilts

Abstract

Only a very small amount of physiological data is available about the low fertility (mean litter size is 5.7 ± 0.8) of Hungarian native breed, Mangalica (M), sows. The aim of the present paper is to reveal the differences in preovulatory follicle development and intrafollicular oocyte maturation between M and Landrace (L) gilts, with special reference to the peri- and postovulatory secretion and peripheral concentrations of estradiol-17β (E2), progesterone (P4), and luteinizing hormone (LH). The number of preovulatory follicles was 6.8 ± 1.4 and 19.6 ± 6.6 in M and L gilts, respectively. A lower degree of cumulus expansion and a lower percentage of mature oocytes (TI/M II) was noted in M. Higher LH and E2 peak levels, a longer E2 to LH peak interval, and lower embryo survival was confirmed. Interestingly, despite the lower number of corpora lutea, a higher peripheral blood level of P4 was shown in M than in L gilts. Both diminished follicular development and protracted oocyte maturation may be involved in low fecundity in M, and the present findings may explain these reproductive phenomena.