Short Communication Superovulatory Ovarian Response in Mangalica Gilts is Not Influenced by Feeding Level I Egerszegi 1 , W Hazeleger 2 , J Ra´tky 1 , P Sarlo´s 1 , B Kemp 2 , E Bouwman 2 , L Solti 3 and K-P Bru¨ssow 4 1 Research Institute for Animal Breeding and Nutrition, Herceghalom, Hungary; 2 Department of Animal Science, Wageningen University, Wageningen, The Netherlands; 3 Department of Obstetrics and Reproduction, Faculty of Veterinary Science, Szent Istva ´n University, Budapest, Hungary; 4 Department of Reproductive Biology, Research Institute for the Biology of Farm Animals, Dummerstorf, Germany Contents The aim of the study was to compare how different feeding levels affect the ovarian potential of follicular development and oocyte maturation in response to superovulatory treatment in native Mangalica (M, n ¼ 17) compared with Landrace (L, n ¼ 20) pigs. Gilts of both breeds were fed high-energy (HI–2.5 kg) or low-energy (LO – 1.25 kg) feed during oestrus synchronization (15 days of RegumateÒ feeding) till the time of oocyte aspiration (Day 6 after RegumateÒ). Follicular growth was stimulated by the administration of 1000 IU equiue choriou gonadotropiu (eCG) 24 h after RegumateÒ treatment, and ovulation was induced by injection of 750 IU human choriou gonadotropiu (hCG) 80 h after eCG admin- stration. Ultrasound (US) investigation was done three times (4–10 h before, and 40–44 and 72–74 h after eCG administra- tion) for the observation of follicular development. Oocyte and follicular fluid (FF) were collected endoscopically 34 h after hCG injection. Cumulus–oocyte complexes were evaluated, their morphology determined, and thereafter fixed and stained for chromatin evaluation. Oocytes were classified as meiosis- resumed (germinal vesicle breakdown, diakinesis, metaphase I to anaphase I) or matured (telophase I and metaphase II). FF concentrations of oestradiol and progesterone were measured by validated radioimmunoassays. In L gilts, differences were observed between HI and LO in the number of preovulatory follicles (32.3 ± 10.5 vs 17.1 ± 12.3, p < 0.05), but not in M (25.3 ± 2.9 vs 28.8 ± 7.3, p > 0.05). Initial follicular growth was not affected by feeding levels; however, preovulatory follicle size was larger in M (7.1 ± 0.9 and 6.9 ± 1.1 mm vs 5.7 ± 0.7 and 5.5 ± 0.8 mm; p < 0.05). No differences were obtained with relation to mature chromatin configuration in both breeds (L gilts: HI – 70% and LO–67% vs M gilts: HI – 67% and LO – 63%). A twofold higher oestradiol concentra- tion was detected in FF of HI-M and LO-M (29.6 ± 6.8 and 30.9 ± 10.3 ng/ml respectively) compared with that of L (16.9 ± 9.7 and 17.9 ± 3.6 ng/ml, respectively; p < 0.05). The mean FF progesterone level was nearly fivefold higher in M (2020.4 ± 1056 and 1512.2 ± 1121.8 ng/ml) compared with L (386.2 ± 113.7 and 298.8 ± 125.9 ng/ml, p < 0.05). The results indicate an influence of the feeding of altered energy on the number of recruitable preovulatory follicles in modern Landrace but not in native Mangalica breed. More- over, the follicular steroid hormone milieu differs between Landrace and Mangalica gilts but not depending on feeding levels. Oocyte maturation was not affected by diet. Introduction An influence of feeding level on the size of the preovulatory follicle pool, ovulation rate and fertiliza- tion capacity of oocytes has been demonstrated previ- ously in pigs of different breeds (Clark et al. 1973; Dailey et al. 1975; Ashworth 1991a; Beltranena et al. 1991; Zak et al. 1997; Ashworth et al. 1999). Low nutrition level effects delayed puberty, increased wean- ing to oestrus interval, decreased ovulation rate and embryonic survival (Prunier and Quesnel 2000a,b; Soede et al. 2000). However, till now there is no information on the influence of altered feeding level on reproductive performance, and especially on follicular development in extensive housed Mangalica pigs. Mangalica is a native Hungarian pig breed, the most typical swine in Hungary until the middle of the last century. It is a fat-type, curly haired swine with relatively low reproductive perform- ance, but strong motherliness and good adaptability to extensive housing conditions (Egerszegi et al. 2003a; Bru¨ssow et al. 2005). The present study aimed at studying whether different nutritional levels alter the potential of follicular devel- opment, initiated by superovulatory stimulation, and oocyte maturation in Hungarian Mangalica compared with Landrace gilts. Materials and Methods Altogether 17 Mangalica and 20 Landrace gilts were studied. Age and body weight of Mangalica and Land- race gilts were 11–12 months, 95–105 kg, and 7–8 months, 95–100 kg, respectively. According to pre- vious data (Ga´bos 1935), sexual maturation of the two breeds is comparable at these ages. Oestrus cycle of all animals was synchronized by 15-day-long feeding of RegumateÒ (Hoechst-Roussel, Paris, France) (20 mg per gilt per day). Follicle development was stimulated with administration of 1000 IU eCG (FolligonÒ, Inter- vet-Hungaria, Budapest) 24 h after the last RegumateÒ feeding. Ovulation was induced 80 h later with 750 IU injection of hCG (ChoriogoninÒ; Richter Gedeon, Budapest, Hungary). Both breeds were randomly divided into two nutritional groups. While low-energy-level (LO) nutrition groups (10 Landrace and eight Mangalica gilts) received 1.25 kg per day dosage, high-energy-level (HI) groups (10 Landrace and nine Mangalica gilts) were fed 2.5 kg daily (digestable energy (DE) 12.7 MJ/kg). The different nutrition diets were given during the entire treatment period. Follicular size development was monitored by ultrasonography (US) using a 5 MHz-probe (Pie Med- Reprod Dom Anim 42, 441–444 (2007); doi: 10.1111/j.1439-0531.2006.00790.x ISSN 0936-6768 Ó 2007 The Authors. Journal compilation Ó 2007 Blackwell Verlag