Detection of mutational sites in the CSN1S1 gene and analysis of αs1-casein composition of the milk in Swedish goats (Capra hircus)

Sammanfattning: The total number of goats (Capra hircus) in Sweden is small compared to the Swedish population of cattle and the Norwegian population of goats. Cheese making from goat milk is one of the productions done in Sweden, even though Swedish goats have a low percentage of caseins in the milk (2.1 %) compared to Nubian goats. Caseins are one factor that affect the produced cheese yield from milk. There are four different caseins; αs1-casein (αs1-CN), αS2-casein (αs2-CN), β-casein and κ-casein. Their respective coding genes are CSN1S1, CSN1S2, CSN2 and CSN3. This study focused on αs1-CN and CSN1S1 with the exon 12 due to a deletion in this exon that has been reported at a high frequency (67.6 %) in Norwegian goats. Forty-eight individual goats of the breeds Swedish Landrace goat, Jämt goat, Lapp goat and Göinge goat from all around Sweden were sequenced for exon 12 to be analysed if they carry the Norwegian deletion. In addition, milk samples from some of these goats and bulk milk have been analysed for the proportions of proteins and caseins. The results showed that the deletion did exist in all the Swedish breeds mentioned above and the allele frequency for the deletion was 94.1 %. The alleles G’ and A’ were also detected in the target region and the analysed milk samples showed that 53 % had low expression. Overall, this study gives insights about the deletion occurred at exon 12 of the CSN1S1, which affects the αs1-CN protein.