Effect of Intramammary Device on New Infection Rate, Milk Yield, and Milk Somatic Cell Counts in Maryland Dairy Herds

Abstract

Effectiveness of a polyethylene intramammary device against naturally occurring infections was evaluated in three Maryland herds over 2 yr. Treated cows [62] were fitted with intramammary devices in all quarters of udders. Control cows [62] were sham treated. Rates of new intramammary infection over single lactation in treated and control quarters of primiparous cows averaged 18 and 27%. Reduction of infection rate was due primarily to fewer Corynebacterium bovis infections. Infection rate between multiparous cow treatments were similar. In uninfected quarters cell counts in strippings averaged .11 to .13 × 106/ml and in quarters fitted with intramammary devices concentrations were only .22 to .31 × 106 cells/ml. But in infected quarters with intramammary devices, cell counts of strippings were 1.38 to 1.48 × 106/ml. Concentrations of somatic cells of strippings in infected quarters without devices averaged .48 to .63 × 106/ml. Dairy herd improvement cell counts for primiparous and multiparous cows with and without intramammary devices were similar and averaged .2 × 106/ml. Neither milk nor fat production differed. The intramammary device as currently designed is incapable of stimulating a leukocytosis sufficient in stripping milk to prevent intramammary infection. © 1984, American Dairy Science Association. All rights reserved.