Interpretive Summary: Relationships among intramammary health, udder and teat characteristics, and productivity of extensively managed ewes
By Anne Zinn
A paper recently published in the Journal of Animal Science evaluated the relationships among intramammary health, udder/teat characteristics, and productivity of extensively managed ewes. Clinical mastitis in sheep is an economically important consideration and can lead to increased ewe turnover and animal health cost, and reduced lamb survival /growth. Signs of clinical mastitis are easier to identify, but a subclinical infection presents no visible signs; however, it can be detected through screening milk samples. Unfortunately, collecting milk samples in a commercial setting is cost-prohibitive and impractical. Research has reported associations between udder morphometry and health in non-dairy ewes and may serve as a more practical selection tool.
The objective of the present study was to identify cultivable microbial species in milk, evaluate somatic cell count thresholds associated with intramammary infection, and estimate relationships between udder and teat morphometric traits, somatic cell count, and ewe productivity. This research is different from previous projects in the US because extensively managed ewes were sampled across two flocks in similar shed-lamb management systems whereas previous research was limited to a single flock.
Results showed that an abundance of microbial species potentially involved in the pathogenesis of mastitis were frequently isolated in milk from healthy-appearing ewes. In addition, it was determined that milk somatic cell count can be used to infer intramammary infection status in extensively managed ewes, but that the thresholds were variable, and phenotyping is cost- and labor-prohibitive at the producer level; while significant correlations were detected among many udder and teat conformation traits, most were not consistently predictive of ewe somatic cell count. It would be useful if more easily measured indicator traits for selection were identified. Further research investigating effective methods of reducing mastitis are warranted.