A linear evaluation system for udder traits of dairy ewes

A method of linear udder trait appraisal proposed for sheep has been applied to 2015 ewes of the Churra breed. It is based on scoring five traits: udder depth, udder attachment, teat placement, tear size and udder shape on a nine-point linear scale. Points were scored for the five traits on 5265 occasions. Means approximate 5 points (between 4.48 and 5.16) and standard deviations are close to 1.33 points (between 1.19 and 1.72). The objectivity of the method, measured by repeatability among three classifiers was satisfactory: 0.57, 0.61, 0.73, 0.60 and 0.68, for udder depth, udder attachment, teat placement, teat size and udder shape, respectively. Analysis of variance showed significant effects for lactation month, flock, classification round, parity number, and classifier. Genetic evaluation to improve mechanical milking aptitude by means of four basic linear udder traits should be carried out using BLUP and including at least the fixed effects of lactation month, flock, classification round, parity number and classifier.