Abstract
The aim of the study was to assess allele frequencies at the CSN1S2 locus in the Sarda goat and the effects of the genotype on milk composition. Two hundred twenty Sarda goats from 20 farms were selected. Individual blood and milk samples were collected during the middle of lactation and daily milk yield was registered. Fat, protein and lactose percentage, freezing point, pH, somatic cell count and total mesophilic count were measured. DNA was analysed with different methods based on PCR. Allele frequencies, the Hardy Weinberg (HW) equilibrium and the correlations between milk yield and composition and the genotypes were calculated. F (0.400) and A (0.330) alleles showed the highest frequency. D and 0 alleles were not found. Genotype frequencies were the following: AA, 0.136; AB, 0.009; AC, 0.082; AE, 0.032; AF, 0.264; CC, 0.023; CE, 0.023; CF, 0.250; EF, 0.077; FF, 0.105. The population was in HW disequilibrium. No link between the genotypes and milk yield, chemical, physical and cytological parameters was found.
Highlights
Breeding and the improvement of autochthonous breeds is an effective choice to improve animal husbandry in some developing areas
Seven alleles have been identified at the CSN1S2 locus and these are associated with three different levels of αs2-casein in milk
Farms were similar in animal management which was in accordance with traditional Sardinian goat farming: goats were exclusively fed pasture on a Mediterranean shrubland, without any concentrate supplementation and the pasture composition was similar among the farms; they were hand-milked once daily in the morning and in all the flocks the udder was not cleaned before milking; reproduction was based on natural mating and sex ratio was 1/18; kids were milk fed by their dams and weaned when they were about six weeks old; some pens and a shelter for milking were the only facilities on the farms
Summary
Breeding and the improvement of autochthonous breeds is an effective choice to improve animal husbandry in some developing areas. Sarda selection schemes have still not considered the qualitative traits of the milk, such as the genetic characterization of casein variants, which are correlated with the chemical and technological properties of goat milk (Barbieri et al, 1995). The study of these characters in other species and breeds has allowed the enhancement in value of their products. Several studies evidenced that the four goat casein genes are polymorphic (Caroli et al, 2006) This variability is an important factor in genetic improvement and permits a diversification of milk production, allowing choice for the right genetic basis for the production of cheese, drinking or hypoallergenic milk (Ramunno et al, 2007). The aim of this research was to analyse the genetic structure at the CSN1S2 locus in Sarda goats and the possible correlations between its genotype and milk parameters
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