Breeding mastitis-resistant cows
Selecting for disease- resistant cows has become a reality for farmers around the globe as genetic developments continue to advance.
Clinical cases that are missed can dramatically increase the bulk milk somatic cell counts (SCC) because they produce very high numbers of somatic cells.
Early detection and treatment of clinical mastitis in the calving period reduces the risk of severe cases developing. It also reduces the likelihood of infection being passed to other cows, and the development of chronic infections.
By recording cow identity and antibiotics used for all cases, the numbers of clinical cases and responses to treatment can be monitore.d
A swollen quarter will appear larger than other quarters on the same cow or may cause the cow to appear lame.
Cows with suspect udders should have their udders felt, or palpated, to check for hardness, heat and swelling. Foremilk should be stripped and checked for signs of mastitis.
Milk containing bacteria can be spread from cow-to-cow when stripping cows.
Gloves should always be worn when checking cows for mastitis, as they are easier than bare hands to rinse and keep clean.
A good practice is to disinfect gloved hands after stripping a cow with clinical mastitis e.g. by dipping gloved hands in a 1% iodophor solution or rubbing with medicated teat wipes.
Collect milk samples for culture to identify the bacteria involved.
Milk culture samples are recommended to help identify which bacteria are involved, if a herd problem emerges.
The right technique must be used to collect samples, otherwise the samples will be contaminated by bacteria from the outside of the teats.
Ask your veterinarian to show you the correct technique. Milk samples can be collected from clinical cases before starting treatments, and stored frozen.
A selection of these samples can be sent to laboratory at a later date if:
- Cows are not responding to treatment e.g. more than 20% of cases are receiving a second course of treatment.
- If concerned about the number of clinical cases occuring during calving e.g. exceeding 4 clinical cases in the past 50 calvings.
- If concerned about the number of clinical cases during lactation.
Hold Milk Back
Ensure each cow has exceeded her antibiotic dry cow treatment (DCT) minimum dry period before putting her milk in the vat or selling her calf.
Ensure that milk from the colostrum period (first eight milkings) is not included in the supply vat.
For milk quality reasons, all cows should have their colostrum milk withheld from the vat for at least eight milkings after calving (10 milkings for heifers and induced cows).
Different arrangements are in place for farmers that supply colostrum to the dairy company.
For cows that have received an antibiotic DCT, a withholding period for milk after calving is specified for each product.
Accurate record keeping is critical for withholding period management and preventing DCT residues from causing an inhibitory substance (IS) grade.
All DCT products are registered with a specified minimum dry period after treatment. If a cow calve within this time, witholding periods for milk and calf meat may be much longer than in the usual situation.
Withold milk for recommended number of milkings and ensure udders are completely milked out. At the start of the season, when the number of cows producing milk for the vat is low, cows with undetected clinical mastitis can cause the bulk milk SCC to increase dramatically and may cause a SCC grade.
Check all cows with a rapid mastitis test (RMT) before moving them from the colostrum herd to the milk supply herd. High SCC cows (cows with a positive RMT result) should be kept in the colostrum herd for an extra 2-4 milking to allow the mastitis to self-cure or turn clinical, and reduce the risk of a SCC grade.
