The effects of genotype, milking time and teat-end vacuum pattern on the severity of teat-end hyperkeratosis

The importance of dairy cow breed and milking machine factors in the development of teat-end hyperkeratosis (HK) was investigated in four experiments. In Experiment 1, the teat characteristics and HK levels of 29 Montebeliarde, 27 Normande, 26 Holstein-Friesian and 26 Irish-Friesian spring-calving cows were classified. Montebeliarde cows had a lower (P < 0.001) HK score at each stage of lactation and had a higher (P < 0.001) number of teats with flat teat-ends than Holstein-Friesian cows. HK was higher (P < 0.001) in front teats than in rear teats in all breeds. In Experiment 2, 48 high genetic merit (100% Holstein-Friesian) cows tended to have higher HK scores than the 48 medium genetic merit (50% Holstein-Friesian) cows. HK was lower (P < 0.001) in early lactation as compared to mid and late lactation. In Experiment 3, the effect of machine cluster-on time on HK score was measured with three groups of 25 Holstein-Friesian cows. Over-milking of cows for 2 min and normal cluster removal at 0.2 kg/min led to similar HK scores. Lower HK scores (P < 0.01) were observed when clusters were removed at a milk How-rate of 0.8 kg/min. In Experiment 4, the effect of two milking systems, which led to differences of 7 kPa in teat-end milking vacuum and of 29 kPa in vacuum fluctuation, on HK was studied using two groups of 28 Holstein-Friesian cows. Higher teat-end vacuum and large vacuum fluctuation did not have a deleterious effect on HK. HK increased (P < 0.001) with each stage of lactation and was higher in front teats at all lactation stages.