Mastitis

By Dr Nik Cronin, Forbes District Veterinarian

We are receiving a lot of calls and doing farm visits to investigate losses in lambing ewes at the moment. Issues arising for each situation are fairly varied, however there is one problem that is quite frequent and surprising a lot of people with its impact, and that is mastitis. This also follows on from a high incidence reported in the 2020 lambing season.

In early and peak lactation the udder is clearly a high functioning organ. When a ewe is in good body condition, and feed and nutrients are readily available, the udder produces milk in response to output - which means the more the lamb/s drink, the more milk the ewe makes.

The primary route of infection in mastitis is up through the teat. It has a little sphincter at its tip which is stimulated to open in response to suckling, and close when feeding is finished. Bacteria can get into the teat during feeding - from the lamb’s mouth, or after feeding before the teat closes - from the environment. A weak or damaged teat may also let environmental bacteria in any time. Once bacteria enter the udder they can set up camp quite comfortably and the outcome depends on the type of bacteria and the ewe’s individual defences. The more aggressive bacteria will proliferate and produce toxins which cause obvious damage – a painful, discoloured udder and milk changes. The bacteria and/or toxins can enter the ewe’s blood stream causing septicaemia/toxaemia, with systemic illness and potentially death. Less aggressive bacteria set up more localised infections which the udder is able to ‘wall off’, avoiding the more obvious significant systemic affects. This will result in a lumpy udder and a reduction in milk quality and quantity.

So why the increased incidence, and what can we do?

We suspect the high reported incidence over the last two years has been due to excellent seasonal conditions and abundant feed – ewes are able to produce milk to match demand, whereas in drought years lactation output was often limited by fibre and/or energy shortage. High milk output is then producing big, strong and vigorous lambs, often multiples, which could be causing increased incidence of teat damage. Perhaps tall, damp pastures may also be damaging the teat? Other conditions such as scabby mouth have also been reported more frequently – scabby mouth lesions can affect the udder and teat and weaken infection defences.

Mastitis can be treated using antibiotic and anti-inflammatory treatments, however these are not always practical to administer during lambing. Affected ewes may also be difficult to identify until the disease is advanced. If identification and treatment is possible, then there is likely to be benefit in pulling affected ewes and their lamb out of the flock as it is thought that they can spread the infection to others. Ewes with permanent udder changes should be identified and potentially culled from the flock where possible.

If you have any questions about mastitis you can get in contact with us by calling 1300 795 299.

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