Association between body and udder morphological traits and dairy performance in Spanish Assaf sheep

Abstract. The relationship between 17 body and 8 udder measurements and phenotypic dairy performance were studied using information from 280 Spanish Assaf ewes from 2 to 4 years old belonging to 18 flocks. The influence of the environmental area on the dairy traits was assessed by fitting a fixed model including the flock effect and the age effect. A factor analysis was also carried out to determine the lowest number of independent factors that account for most of the variation in the traits. The flock was statistically significant for performance trait and predicted breeding value (PBV) while the age was only significant in 150 days standardized milk yield (MY150) and daily milk yield (DMY). In general, not much association was found between morphological and dairy performance traits. Few body traits showed significant phenotypic correlations; mainly those related to height, diameters, ears and tail, with the latter being the most correlated but unfavourable for DMY and PBV. Among udder conformation, udder depth and length were the most correlated traits to milk production, while deep udders and short teats were related to lower somatic cell counts. The different traits were classified for analyses into six factors relating mainly to: live weight; production and udder traits; cheese production; stature; teats and udder health; and udder dimensions. Trade of animals was concluded to be unreasonably based on morphological or even on performance traits. The participation of breeders in an appropriate breeding scheme based on accurate genetic evaluations is encouraged.