Phenotypic and reproductive characterisation of kolbroek pigs

Abstract

Indigenous pigs are considered as a valuable component of rural livelihood farming systems in South Africa. However, the population of rural pigs such as Kolbroek are considered stagnated due to the absence of a comprehensive improvement and conservation strategy. Therefore, in domestic pigs (Sus Scrofa domestica), phenotypic and reproductive characterisation are some of the most important characteristics for improved pig production. The objectives of the study were to evaluate the phenotypic characteristics of Kolbroek males and female pigs, to correlate the testicular size with semen parameters and to detect the onset of puberty by hormonal assays in Kolbroek boars and sows then evaluate the reproductive characteristics of the sows following natural mating. A total of 57 Kolbroek pigs (34 sows and 23 boars) were used for phenotypic characterisation. Data for various phenotypic characteristics were evaluated by visual appraisal. Morphometric characteristics such as body weight, body length, chest girth, head length, width of head, ear length, hair length, tail length and number of teats were recorded using a measuring tape. The scrotal measurements were done using a vanier calliper. A total of fifteen ejaculates from three boars were collected using a gloved hand technique method. Semen parameters were evaluated macroscopically and microscopically. Blood was collected randomly from thirteen Kolbroek pigs from the jugular vein every two weeks for 5 months using a 10ml syringe. Blood was then centrifuged at 2400rpm for 14 minutes and the serum was stored at -200C. The serum profile of Luteinizing Hormone (LH), Follicle Stimulating Hormone (FSH) and Estradiol (E2) of the gilts were determined using Elisa kits. Data were analysed using the Statistical Analysis System (SAS). The predominant coat colour pattern of the pigs was a patchy black and white colour type. All the pigs had straight long and dense hair and tusks were present only in boars. In all the descriptive characteristics, majority of the sows had a rough skin and ears which projected forward (57.9%). Moreover, majority of boars had erect ears (69.7%). All the pigs had concave heads with a short and cylindrical snout, a straight tail and sows had an average of 10 teats. There were no significant differences (P>0.05) for morphometric characteristics, irrespective of the gender. However, sows (123kg) had a significantly higher (P<0.05) body weight compared to boars (114kg). There was a significantly positive correlation (P<0.05) between bodyweight and testicular size (r = 0.90). There was also a highly positive correlation (P < 0.01) between testicular size and sperm concentration (r = 0.47) as well as total motility (r = 0.30). Moreover, there was a highly positive correlation between body weight and semen pH (r = 0.91). A significant positive correlation was observed between body weight and semen volume (r = 0.80) as well as sperm concentration (r = 0.90). A highly significant positive correlation was also observed in testicular size and semen volume (r = 0.90). Weak positive correlations (P>0.05) were found between semen pH and sperm concentration (r= 0.18) and semen volume (r= 0.18), although not significant. Furthermore, a weak positive correlation was observed between body weight and sperm motility (r= 0.30). There was strong positive correlation (P<0.05) between sperm motility and semen volume (r= 0.66), pH (0.78) and sperm concentration (r= 0.60). There were no significant differences (P>0.05) for hormonal serum concentrations in Kolbroek sows. There was a significant increase (0.22-0.35ng/ml) in serum concentrations of LH, FSH and E2 in all sows from 3 to 7 months of age. In conclusion, Kolbroek pigs have a patchy black and white coat colour. The head was concave in form and the ears were erect and projected forward. It was also found that the effect of gender was not significant on all body weights and measurements in Kolbroek pigs, except for body length. It was indicated that the measurements of testicular size and bodyweight of Kolbroek boars was positively correlated with semen volume. The age of attainment of puberty of Kolbroek sows was found to be 3 months. The study showed that phenotypic and reproductive characteristics are useful in selection, identification and conservation of South African Kolbroek pigs.