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

Abstract

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.