Milk protein polymorphisms have a significant influence on milk quantity and composition. Kappa-casein is of special interest due to its known relationship with milk quality. In goats, a number of allelic variants have been identified, primarily classified into two groups. Group BIEF alleles (D, E, K, and M) have been shown to have a positive effect on milk yield and technological properties, while group AIEF, the remaining alleles, have a less positive influence on milk composition. The aim of this study was to investigate genetic variation in the kappa-casein genotype of South African goats. PCR-RFLP and DNA sequencing were performed on 68 and 77 samples, respectively. In addition, 84 milk samples were analyzed for milk composition. RFLP analysis revealed that the A and/or B alleles were the most frequent in the populations studied. A frequency of 0.00 was observed for the BIEF variants using DNA sequencing. In all goat types included, the B allele was the most common, with frequencies ranging from 60% in SA Boer goats to 100% in Saanens. The B’ allele had lower frequencies of 0.357 and 0.207 in SA Boer goats and local goat types, respectively. The H allele was present at low frequencies in local goat types (10.3%) and in SA Boer goats (3.6%), but was absent in Saanens. AMOVA results indicated that most of the total variation occurred within populations (80.66%) with the remainder of the variation (FST = 0.1934; p < 0.01) occurring due to genetic differences between populations. / Dissertation (MSc(Agric))--University of Pretoria, 2009. / Animal and Wildlife Sciences / unrestricted

Darbo užduotis: 1. Išanalizuoti literatūrą nagrinėjama darbo tema. 2. Įvertinti tešmens paruošimo melžimui įtaka pieno srautui ir somatinių ląstelių skaičiui; 3. Nustatyti pieno srauto įtaka somatinių ląstelių skaičiui. Duomenys tyrimams rinkti melžiant karves tendemo tipo melžimo aikštelėje ir stovėjimo vietoje į pieno liniją. Kontrolinių melžimų metu buvo fiksuojami šie rodikliai: karves stovėjimas melžimo aikštelėje iki tešmens ruošimo pradžios laikas (min), tešmens ruošimo melžimui laikas (min), melžimo trukmė (min), pieno kiekis (kg). Iš ALPRO sistemos registruojamų melžimo duomenų, buvo naudojama: vidutinė pieno tekėjimo srovė (kg/min.), pieno srovės pikas (kg/min.). Tyrimuose buvo naudojama programinė įranga : (Exsel, Word) ir SPSS-statistinis paketas. Išvados: 1.Ruošiant tešmenį melžimui ilgiau kaip 0,20 min., iš karvės primelžiame daugiausiai pieno ir buvo nustatytas didžiausias vidutinis pieno srautas, bei pieno srauto pikas. 2. Tarp pieno kiekio ir melžimo trukmės buvo nustatyti statistiškai patikimi koreliacijos koeficientai (P<0,001). 3. Melžiant karves tendemo tipo aikštelėje tarp vidutinio pieno srauto ir pieno kiekio bei melžimo trukmės nustatyta statistiškai patikima koreliacija. (P<0,001). 4. Tešmens ruošimo laikas neįtakoja somatinių ląstelių skaičiaus piene. 5. Besikeičiantis pieno srauto pikas somatinių ląstelių skaičiui piene įtakos neturėjo. 6. Ilgiau stovint karvėms melžimo aikštelėje iki tešmens ruošimo pradžios, pieno srauto pikas ir vidutinis pieno... [toliau žr. visą tekstą] / Task of work: 1. To analyze the theme of work, analyzed by literature; 2. To assess the impact of udder preparation on milk flow and somatic cells count; 3. To determine the impact of milk flow on somatic cells count. The data for researches were amassed while milking cows in tandem milking parlour and in standing place to milk line. During controlling milking there were been fixed these rates: the time of cow’s standing in milking parlour until the beginning of udder preparation (min), the time of udder preparation for milking (min), duration of milking (min), milk quantity (kg). From milking data, registered by ALPRO system, there was used: an average milk flow (kg/min), milk flow peak (kg/min). Software used in these studies: (Excel, Word) and SPSS-statistical package. Conclusions: 1. When preparing udder for milking longer than 0,20 min, we get maximum quantity of milk, and an average milk flow and milk flow peak was determined as the highest. 2. Statistically reliable correlation coefficients were determined between milking duration and milk quantity (P<0,001). 3. When milking cows in tandem milking parlour, it was determined statistically reliable correlation between an average milk flow and milk quantity and milking duration (P<0,001). 4. The time of udder preparation has no influence on somatic cells count in milk. 5. Changing milk flow peak had no influence on somatic cells count in milk. 6. When cows stand longer in milking parlour till the beginning of udder... [to full text]