Case report: High prevalence rate of ovine mastitis, caused by coagulase-negative staphylococci and predisposed by increased gossypol consumption
A case of unusually high (>94%) prevalence of mastitis in a flock of dairy sheep, which was caused by coagulase-negative staphylococci (cnS) and associated with increased gossypol consumption, is presented. The animals were given a ration containing 25% cottonseed meal, whilst the farmer complained of significantly reduced milk yield. Various clinically detectable abnormalities were found in the mammary glands; the California mastitis test (CMT) performed was always positive (≥1). Bacterial species isolated from mammary secretion samples were cnS (n=54), Staphylococcus aureus (n=5), Bacillus spp. (n=5), Escherichia coli (n=3) and Arcanobacterium pyogenes (n=2). During the post mortem examination, pathological findings characteristic of rumen acidosis were found in the mammary gland, macroscopic and histological lesions characteristic of chronic mastitis were seen. Bacteria (cnS, n=23; Bacillus spp., n=3; S. aureus, n=2; E. coli, n=2) were also isolated from mammary tissue samples. Gossypol was detected in pooled milk samples collected from the ewes. A hypothetical model involving the high prevalence rate of staphylococcal mastitis with the increased dietary intake of gossypol is proposed. © 2003 Elsevier B.V. All rights reserved.