Follicular development and preovulatory oocyte maturation in Hungarian Mangalica and Landrace gilts

Abstract

Abstract. Preservation of native pig breeds of different values has got increasing public interest. Hungarian Mangalica, likewise other native races, became uninteresting because of economic reasons or other characteristics, and were replaced by modern breeds. Its population decreased rapidly and reached a critical level. However, the exceptional taste of the meat, and the robustness and motherliness do support the propagation of this breed. Nevertheless, low prolificacy and marked seasonality remains a problem. The aim ofthe present study was to find possible implications of the physiological basis with regard to the low fecundity. Therefore, preovulatory follicular development and intrafollicular oocyte maturation of Mangalica and of Landrace gilts were compared. A total of 18 pubertal Blond and Swallow Belly Mangalica and 19 Landrace gilts (8.5 to 9 month of age, body weight of 120 to 125 kg) were used. Oestrus of gilts was synchronized by feeding Regumate®, follicular growth was stimulated by administering 1,000 IU PMSG 24 h after the last Regumate® feeding and the LH peak simulated with 750 IU hCG 80 h after PMSG. Cumulus-oocyte-complexes (COCs) were recovered 34 h after hCG by endoscopic Ovum Pick Up. Follicular fluids from follicles per ovary were pooled and the morphology of COCs was determined. COCs were classified as compact, expanded or denuded. Thereafter, COCs were prepared for evaluation of nuclear configuration. Based on their nuclear status the oocytes were classified as 1) immature – germinal vesicle (GV), with diplotene chromatin; 2) meiosis resumed – G V breakdown, diakinesis, M-I to A-I; or 3) mature – T-I and M-II. The average number (+SD) of preovulatory follicles was 6.8 + 1.4 in Mangalica and 19.6 ± 6.6 in Landrace gilts (p<0.05). Differences were obtained conceming the morphology of recovered COCs between breeds. The per cent of oocytes with compact cumulus was higher in Mangalica compared to Landrace gilts (31 vs. 16 %) but less oocytes possess expanded cumulus (62 vs. 78 %, p<0.05). The meiotic configuration of oocytes was unlike between Mangalica and Landrace gilts. The rate of oocytes with mature chromatin configuration (Telophase I /Metaphase II) was higher (27 vs. 62 %, p<0.05) in Landrace sows. It is assumed that both diminished follicular development and protracted intrafollicular oocyte maturation may be involved in low fecundity in Mangalica.