Frequency, causes and dynamics of palpable udder defects in non-dairy breed ewes

Introduction: The majority of research into ewe udders has been in dairy breed sheep. Udders of extensively farmed non-dairy breed ewes may be assessed by farmers once per year, usually shortly after weaning.

Methods: Several studies were undertaken in commercial and research flocks to investigate the causes and dynamics of palpable udder defects in non-dairy breed ewes.

Results: The most common palpable defects were generalised hard-ness of the udder half or a lump or lumps within the mammary tissue. In 40 New Zealand sheep flocks, around 2.5% of ewes had palpable udder defects shortly after weaning, while in 10 of these flocks an additional 2.4% of ewes were found to have ‘new’ defects when examined a second time 4-6 weeks later. However, studies whereby ewes’ udders were examined four times per year for three years, or six times during lactation, demonstrated that palpable defects are dynamic and transition between defective and normal. Many different species of bacteria were isolated from defective udder halves but the most common were S. aureus, S. uberis and NAS. No bacteria were isolated from 20%–60% defective udder halves. Approximately a third of ewes with a history of udder defects had excessively hard udder halves in the first week of lactation and no milk could be expressed, but these softened and most returned to normal during lactation.

Conclusions: Overall, the studies emphasise that palpable udder defects are relatively common in non-dairy breed ewes. Ewe udders should be palpated at least once per year, ideally after weaning, and it is recommended that affected ewes are culled.

Ethics Approval: These studies were approved by the Massey University research ethics committee.

© 2025 The Authors. © 2025 Australian Veterinary Association.