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 SC C at two samplings 28 days apart on the Dairy Herd Improvement Association test day. Blood samples were obtained for serological analyses of caprine a rthritis-encephalitis virus. Bacterial intramammary infection (IMI) was dia gnosed 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 i mmunodiffusion was 94.3%. Composite SCC as compiled by the Dairy Herd Impro vement 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 lo wer foremilk SCC (1.3 and 1.0x10(6)/ml, respectively) than the infected rig ht and left udder halves (1.74 and 1.66x10(6)/ml), respectively, but only i n the left halves was the difference significant. Halves infected by S. epi dermidis averaged higher SCC (1.8x10(6)/ml) than the halves infected by oth er staphylococci (1.5 x 10(6)/ml). Milk SCC increased as parity increased. (C) 1999 Elsevier Science B.V. All rights reserved.