RELATIONSHIP BETWEEN THICKNESS, CHAPPING AND STAPHYLOCOCCUS-AUREUS COLONIZATION OF BOVINE TEAT TISSUE

Post-milking measurements of teat skin chapping score, teat thickness and colonization by Staphylococcus aureus were determined for 11.5 d. Three teats on each of twelve Holstein cows, free from Staph. aureus i ntramammary infections, were immersed in 1 M-NaOH solution to induce t eat chapping; the fourth teat served as a control. To achieve differen t degrees of chapping, one teat per cow received one immersion after e ach milking for three consecutive milking periods, a second teat recei ved two immersions, and the third teat received one immersion which co incided with the last immersion of the other two teats. All teats were challenged twice with a skim milk broth culture of Staph. aureus (5 x 10(6) cfu) after the first and second milking following NaOH treatmen t. Measures were initiated with the milking following the last Staph. aureus challenges. Tissue thickness of the lateral side of the teat (b arrel) and colonization by Staph. aureus declined with time. Thickness of the teat end varied more erratically. Teat skin chapping score was positively correlated (P < 0.001) with tissue thickness of the barrel and Staph. aureus colonization. Thickness of the barrel was not signi ficantly correlated with Staph. aureus colonization. Barrel thickness as a covariate had a significant effect (P < 0.05) on teat skin coloni zation of Staph. aureus, whereas teat skin score and teat end thicknes s had no significant effect. Thus, thickness of the lateral side of th e teat explained the greatest variation in Staph. aureus teat skin col onization in the model tested.