Effect of polymorphisms at the casein gene cluster on milk renneting properties of the Sarda goat

Abstract This study investigated the influence of casein genes polymorphism on renneting properties of milk from Sarda goats. Milk yield and composition, and renneting properties (rennet coagulation time RCT, firming time k20 and curd firmness a30) were evaluated in 200 multiparous goats from three farms, at monthly intervals from March to July. Animals were genotyped at CSN1S1 , CSN2 , CSN1S2 and CSN3 . Statistical analysis was performed by a repeated measures General Linear Model. CSN1S1 significantly affected milk traits with a lower fat content registered for goats carrying the F allele. The highest protein concentration was recorded for the CSN1S1 AB goats. Milk from CSN1S1 FF homozygote goats was characterized by a delayed k20 and the CSN1S1 AB showed a higher a30. All the parameters were influenced by the CSN2 locus, except milk yield. Polymorphism at CSN1S2 influenced only daily milk yield and a30. The CSN1S2 0 null allele was detected for the first time in this breed. The influence of genotype effect was particularly marked for CSN3 ; RCT and k20 were delayed in CSN3 BB goats and the highest level of a30, 47.88 mm registered for CSN3 AA goats, could be considered remarkable when compared to other goat breeds or populations. In conclusion, this study improved knowledge on the effects of goat casein genes on milk renneting parameters, and could be useful in the future planning of breeding programs and specific dairy products linked to the Sarda breed (PDO/PGI).