You can improve your culling decisions if you know the type of bacteria responsible for mastitis in your herd.

Culling is often needed with Staph aureus infections because they are more difficult to cure, even with Dry Cow Treatment, than infections caused by other bacteria.

Staph aureus can imbed in the udder in tiny abscesses that are protected from antibiotic treatment (both intramammary and injected), resulting in cure rates over the dry period of only 50 to 80%. This means there are always some cows that carry the infection into their next lactation, potentially spreading it to young, healthy animals.

So, if you have enough heifers coming into the herd, it is a good idea to have a discretionary cull of persistently infected cows. 

For cows infected with Streptococcal mastitis (caused by Strep ag, Strep dysgalactiae or Strep uberis infection), the chance of cure after Dry Cow Treatment is closer to 90%. Although they often have high cell counts, cows infected with this type of mastitis in one lactation are usually better candidates to treat than to farewell.

Review the cultures in your herd over the last lactation and plan to get some more if you don’t have a good picture of the prime mastitis culprits. Use culling selectively and wisely and your mastitis problems will ease next year.

 For advice on culling decisions, speak to your veterinarian, field officer, herd improvement officer or departmental adviser.

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Why me? Which cows will you choose for culling?

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Keywords
Cull, persistent infection, clinical cases, cell counts