Subclinical mastitis is the inflammation of the udder without visible signs. It is typically caused by bacterial infection. This disease can have important economic and welfare impacts on meat-producing flocks, including udder damage, decreased milk yield, impaired lamb growth, and increased ewe and lamb mortality. In this study, we characterized the prevalence, incidence, and persistence of bacterial pathogens in milk and investigated the potential risk factors of lactation stage, parity, and the number of lambs reared. We collected weekly milk samples from 37 ewes during the first 8 wk of lactation. We found that 33% of samples were infected, with non-aureus Staphylococci responsible for most infections (72%). Other major pathogens included Staphylococcus aureus (8%) and Mannheimia haemolytica (6%). The persistence of infections depended on the pathogen, with 36% of infections curing on their own. The risk of subclinical mastitis increased during lactation for ewes rearing single or multiple lambs, as well as for ewes in their first or second parity, but not for ewes in later parities. Improved knowledge of the major pathogens and risk factors involved in subclinical mastitis is important in effectively controlling this disease in meat-producing flocks.

Read the full article in the Journal of Animal Science.