HYPERKERATOSIS OF THE TEAT DUCT ORIFICE IN THE DAIRY-COW

Teat orifice hyperkeratosis, a commonly observed condition in dairy co ws, has been considered a consequence of machine milking and the degre e of hyperkeratosis may be increased by a poor milking system. A fully illustrated technique is described which uses a scoring system from 0 for a perfect orifice to 5 for an orifice significantly enlarged with extensively protruding fronds of teat duct keratin. A range of scores found in 25 commercial dairy herds is presented. The scores have been averaged for each cow and the markedly skewed distribution corrected by a square root transformation. This scoring procedure allows compara tive measures of hyperkeratosis within and between herds. An 8-fold di fference (0.17-1.31) in herd average score was found. Within all herds the score increased with lactational age of the animals and peaked, f or any lactation, some 3-4 months post partum, declining as the animal s dried off. There was no significant relationship between mean somati c cell count and degree of hyperkeratosis at the herd level. This impl ies that such chronic pathological changes are unlikely to be related to the level of intramammary infection. It appeared that some hyperker atosis is an obvious and probably natural response to milking and occu rs in a significant proportion of animals in all herds although often only to a slight degree. Much more hyperkeratosis may be a measure of the performance and management of the herd. The genetic influence is u nknown. Higher yielding cows will score higher as they milk for longer , but generally high scores may reflect consistent and possibly consid erable overmilking. Hyperkeratosis may be an indicator of the quality of management and show the level of attention being paid to the welfar e of the herd.