Udder and teat morphology related to mastitis resistance: a review.

Annual losses by mastitis are estimated to be in excess of two billion dollars in the United States. Udder and teat morphologies have been associated with incidences of mastitis without clear conclusion on the closeness. Streak canal diameter was correlated with udder health, but it is difficult to measure. Udder depth and teat-end shape have been associated with udder health. Selection to reduce frequencies of cows with deep udders and flat, disk, or inverted teat ends may reduce mastitis incidence. Heritabilities of udder morphology are moderate to high, and a single score during the lifetime of a cow may be adequate for selection. There is no concensus in the literature on relationships between mastitis and teat size, general teat shape, teat-end lesions, teat pigmentation, or milk flow rate. Different breeds, milking procedures, measures of mastitis, and statistical procedures may account for different conclusions. Genetic approaches to improve mastitis resistance of dairy cattle seem warranted. This paper attempts to summarize evidence dealing with possible physical bases for genetic variation associated with mastitis in dairy cattle.