Genetic and environmental factors affecting buffalo milk aptitude to cheese making

Individual milk samples were collected every month from 76 buffalo cows during the lactations performed in 1990, 1991 and 1992. At each monthly test, milk produced at the two daily milkings was measured and a milk sample was collected, on which the following parameters were determined: (i) fat, protein, lactose, SNF and dry matter percentage; (ii) pH; (iii) genetic typing for casein variants (αs1-Cn, αs2-Cn, β-Cn and k-Cn) through immunoelectrophoretic techniques; (iv) clotting aptitude through the following: duration of enzimatic phase (T), clotting speed (K) and curd firmness (a) at a definite time. Milk yield in the standard 270 days lactation and corresponding protein yield were calculated; both values were transformed in the corresponding mature equivalent (i.e., to a 5 year old buffalo cow calving in January) in order to detect differences between casein genotypes. Protein polymorphism at αs1-Cn locus (B and C variants) and at αs2-Cn locus (A, B and C variants) was evidenced, while on the contrary, only A variant was found at β-Cn locus and only B variant at k-Cn one. B variant of αs1-Cn has an allele frequency of 0.605 while variant A of αs2-Cn has an allele frequency of 0.704. Milk produced by buffaloes with αs1-Cn CC or αs2-Cn AA genotypes has the best clotting properties, with a shorter enzymatic stage, shorter clotting time, shorter and firmer curd. When considering the four loci genotype (αs1-, αs2-, β- and k-Cn), the most favourable to clotting is CC-AB-AA-BB, which has the shortest enzymatic stage, the firmest curd, the highest milk yield and protein in the standard lactation (270 days). Therefore, the evaluation of genotype effects on the quanti-qualitative milk production could be done taking into account all four loci considered and not the single locus. Also environmental factors highly affect the majority of cheese making parameters. Calving number, milking and monthly test are most important.