Defects and bacterial pathogens in udders of non-dairy breed ewes from New Zealand

The objectives of this study were to identify the prevalence, incidence and range of udder defects in non-dairy breed ewes in New Zealand and to investigate the range of bacteria present in milk samples. The udders of 5700 mixed-age ewes on 11 sheep farms in the lower North Island of New Zealand were examined and scored at weaning. The majority were examined again 4-6 weeks later. Milk samples were aseptically collected from 110 ewes (195 udder halves) for bacterial culture. At the initial (weaning visit), 2.5% of ewes had udder defects, while 4-6 weeks later, an additional 2.4% of the remaining ewes had developed defects in the intervening period. In total, across the two visits, 4.5% of ewes were identified with udder defects (inter-farm range 2-7%). The most commonly identified defects were lumps in one udder half, followed by diffuse hardness in one udder half. A range of bacterial species were isolated from milk samples but Staphylococcus aureus was the most common species. These results demonstrate that udder defects are common in ewes in New Zealan, and farmers are recommended to examine ewes' udders at least 4-6 weeks after weaning so that defective ewes are not bred.