Heritability of teat-end shape and the relationship of teat-end shape with somatic cell score for an experimental herd of cows.

Teat-end shapes were categorized for 1443 Holstein cows with 3582 lactations, in the Iowa State University herd at Ankeny, approximately 40 d postpartum between 1970 and 1995. Frequencies of teat-end shapes were as follows: round, 52.2%; prolapsed, 0.8%; flat, 14.2%; plate, 3.4%; funnel, 8.9%; and mixed, 20.5%. Cows were coded as mixed if all four teat-end shapes were not the same. Heritability estimates were obtained with an animal model with pedigrees traced back to registration numbers roughly conforming to birth year 1955. The heritability estimates for first, second, and third and later lactations were 34, 21, and 13%, respectively. Lactation averages for linear somatic cell scores were adjusted for days in milk, and month and age at calving, and were available for 255 cows with 431 lactations categorized from 1992 to 1995. Frequencies of teat-end shape on the 255 cows were as follows: round, 58%; prolapsed, 3%; flat, 11%; plate, 2%; funnel, 6%; and mixed, 20%. Least-squares means of somatic cell score for categories of teat-end shape were computed from a mixed model that included year, parity, and teat-end shape as fixed effects and cow as a random effect. Teat-end shape did not significantly affect somatic cell score.

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

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.