Prevalence of subclinical intramammary infection caused by Staphylococcus epidermidis in a commercial dairy goat herd

One herd with 138 lactating goats that had a high somatic cell count (SCC) in bulk tank milk was studied. Foremilk was sampled for bacteriology and SCC at two samplings 28 days apart on the Dairy Herd Improvement Association test day. Blood samples were obtained for serological analyses of caprine arthritis-encephalitis virus. Bacterial intramammary infection (IMI) was diagnosed when the same pathogen was isolated twice from the same udder half. The prevalence of IMI was 34%. Most of the pathogens isolated (95.7%) were Staphylococcus spp. Staphylococcus epidermidis was the predominant species (66.7%), and most of these had similar biochemical profiles. Seroprevalence of caprine arthritis-encephalitis virus infection as assayed by agar gel immunodiffusion was 94.3%. Composite SCC as compiled by the Dairy Herd Improvement Association averaged 10(6)/ml for the first sampling and 1.27x10(6)/ml for the second sampling. Uninfected right and left udder halves had a lower foremilk SCC (1.3 and 1.0x10(6)/ml, respectively) than the infected right and left udder halves (1.74 and 1.66x10(6)/ml), respectively, but only in the left halves was the difference significant. Halves infected by S. epidermidis averaged higher SCC (1.8x10(6)/ml) than the halves infected by other staphylococci (1.5 x 10(6)/ml). Milk SCC increased as parity increased. (C) 1999 Elsevier Science B.V. All rights reserved.