Heritabilities of teat end shape and teat diameter and their relationships with somatic cell score.

Abstract

Teat end shapes were categorized for 1740 Holstein cows with 2261 lactations in nine herds. Frequencies of teat end shapes were pointed, 7%; pointed disk, 1%; round, 43%; round ring, 16%; round flat, 5%; round disk, 11%; flat, 6%; disk, 10%; and inverted, 0.8%. Teat diameters were measured 1.5 cm from the end of the teat. Teat end lesions were visually classified into four categories: no lesion, rough ring, very rough, and ulcerated, raw appearance. Repeatability estimates for teat end shape and teat diameter were 0.75 and 0.36, respectively. Heritability estimates of teat end shape for first, second, and all lactations combined were 0.53, 0.44, and 0.56, respectively. Teat diameter heritabilities were 0.23, 0.27, and 0.35, respectively. The genetic correlation between teat end shape and teat diameter was 0.64. Linear somatic cell scores (SCS) averaged across lactation and adjusted for days in milk and for month and age at calving were available for single lactations of 1506 cows. Least squares means of SCS for categorically scored teat end shapes were computed from a model that included herd date, parity, days in milk, lesion, and teat diameter. Teat end shape and teat end lesion did not significantly affect SCS. Wider teat diameters were associated with higher SCS. Predicted transmitting abilities for SCS and udder composite index scores were available for 113 sires that had five or more daughters with teat end scores. Predicted transmitting abilities for SCS were significantly associated with udder composite index but not with sire solutions for teat end shape.