To examine the development of teat end callosity thickness and roughness in
early lactation and to quantify cow factors of interest, a system to class
ify teat end condition was developed. A distinction was made between rough
and smooth rings around the teat orifice. In addition, a classification of
the degree of callosity was developed. Kappa coefficients for the repeatabi
lity of scoring by this classification system by different workers were 0.7
1 for teat end callosity thickness and 0.86 for teat end callosity roughnes
s. The teat end callosity classification system was used for a longitudinal
study with 40 cows during the first 14 wk of lactation. Models were built
to predict teat end callosity thickness and roughness, machine-on time, and
milk yield. For the response variables, teat end callosity thickness, mach
ine-on time, and milk yield, the consecutive measurements appeared to follo
w a lactation curve model with a subject-specific general slope and interce
pt. Teat end callosity increased rapidly the first 8 wk. Cow factors such a
s days in milk, parity, machine-on time, and teat end shape were associated
with the degree of teat end callosity, and the probability of the callosit
y ring to become rough. Teat end callosity thickness did not decrease withi
n the 14-wk trial period for most teats. Pointed or round teat ends showed
more callus than inverted teat ends. Longer machine-on time resulted in a h
igher probability of the callosity ring to become rough. Rear teats showed
less callosity than front teats in this study.