A BENEFIT TO COST-ANALYSIS OF THE EFFECT OF PREMILKING TEAT HYGIENE ON SOMATIC-CELL COUNT AND INTRAMAMMARY INFECTIONS IN A COMMERCIAL DAIRY-HERD

A field trial was conducted to determine the effect of premilking tent disinfection (predipping) on several measures of mastitis in a commer cial dairy farm where the predominant organisms isolated from intramam mary infections were coagulase negative Staphylococcus spp. Cows were: randomly assigned to a treated (predipped with 0.5% iodine germicide plus ''good udder preparation) or a control group (''good udder prepar ation'' alone). Sterile composite milk samples were collected at the i nitiation of the trial and on an approximately bimonthly basis through out the duration of the trial. There was no difference in the prevalen ce of isolation of coagulase-negative Staphylococcus spp. from composi te milk samples obtained during the 6 herd cultures. The incidence rat e for clinical mastitis in the control group was 1.38 cases per 1000 c ow days. The incidence rate for clinical mastitis in the treatment gro up was 1.06 cases per 1000 cow days. The ratio of these 2 was 1.3, sug gesting a higher rate in the control group, but the ratio was nor stat istically significant (P = 0.34). Logistic regression analysis indicat ed that the effect of treatment group was not significant, although th e coefficient suggested that predipping reduced the risk of clinical m astitis. The benefit to cost ratio of 0.37 indicated that the benefit of reduced incidence of clinical cases of mastitis would not have just ified the added expense required to predip the herd.