Genetic and phenotypic investigation of milk composition and technological properties in dairy sheep

In the last decade, the technological and the nutritional qualities of milk have been extensively investigated because of the worldwide increasing amount of cheese produced and the consumer interest in dairy product features related to human health. In the present thesis the genetic and phenotypic variability of milk composition and technological properties of Sarda dairy ewes were investigated.The use of multivariate factor analysis on milk composition, coagulation properties and cheese yield has allowed elucidating the inner structure of the correlation patterns existing among variables that define milk quality. Four new extracted variables (latent factors) from the original traits, explained about 76% of total variance. Heritability estimates for the factors suggest their use as breeding goals.The study of lactation curve for milk traits during lactation has showed an improvement of cheese yield in late lactation, even though this result could be due to a reduction of curd draining capacity. At the end of lactation were observed the poorest cheese-making aptitude, which could be explained by physiological changes in ewes and relevant modification of milk composition. Stage of lactation, parity and month of lambing were the main factors affecting milk quality traits.The possibility to improve nutritional quality with selection programmes, in particular milk fatty acids profile, is supported by the existence of genetic variability for some fatty acids, as evidenced by our results.