Leitner, G., National Mastitis Reference Center, Kimron Veterinary Institute, Bet Dagan 50250, Israel
Chaffer, M., National Mastitis Reference Center, Kimron Veterinary Institute, Bet Dagan 50250, Israel
Shamay, A., Ruminant Physiology, Institute of Animal Science, Volcani Center, Bet Dagan 50250, Israel
Shapiro, F., Ruminant Physiology, Institute of Animal Science, Volcani Center, Bet Dagan 50250, Israel
Merin, U., Department of Food Science, Institute of Technology and Storage of Agricultural Products, Volcani Center, Bet Dagan 50250, Israel
Ezra, E., Israel Cattle Breeders Association, Caesarea, Israel
Saran, A., National Mastitis Reference Center, Kimron Veterinary Institute, Bet Dagan 50250, Israel
Silanikove, N., Ruminant Physiology, Institute of Animal Science, Volcani Center, Bet Dagan 50250, Israel

The mechanism of the effects of glandular-level subclinical mastitis in dairy sheep on milk yield and on its composition as expressed in curd yield was studied. Thirty-six Israeli-Assaf dairy sheep with one udder half infected with identified coagulase-negative staphylococci and the contralateral gland free of bacteria were chosen. The milk yield of the infected halves was significantly lower than that of the uninfected ones (0.36 vs. 0.76 kg/milking). The somatic cell count and N-acetyl-β-D-glucosaminidase activity were significantly higher in the infected halves than in the uninfected ones. The plasminogen activator and plasmin (PL) activities were significantly higher in the infected glands than in the uninfected ones, whereas plasminogen (PLG) activity and the ratio PLG:PL were significantly lower in the infected glands. Concentrations of Ca2+ did not differ, whereas Ca2+ activity was significantly lower and proteose peptone concentration was 2.4 times as high in the infected glands than in the uninfected ones. Curd yield was significantly lower in the infected glands than in the uninfected ones. © American Dairy Science Association, 2004.