When subclinical mastitis in a herd has been reduced to a very low level (i.e., every cow in the herd less than 100,000 cells/ml), using dry cow treatment only on selected higher risk cows has been considered appropriate by some dairy producers and veterinarians. However, selective treatment may fail to reach 20 to 40 percent of infected quarters in a herd. Also, uninfected quarters not treated at drying off are more likely than treated quarters to become infected during the dry period. It has been shown that when the cow is the unit of risk, a cow with one infected quarter is more likely to suffer another infected quarter than any quarter in an uninfected cow.
Most studies indicate that if the decision is based on economics (i.e., the cost of dry cow therapy compared to the return to the producer), treating every quarter of every cow at drying off is preferable.
The teats must be cleaned and sanitized carefully before infusion. Without proper preparation, organisms present on the teat end may be forced into the udder and result in a severe infection, especially if Gram-negative bacteria are introduced.
The best procedure is to follow these easy steps:
- Clean and dry teats.
- Dip teats in an effective germicidal product. Allow 30 seconds contact time before wiping teats with an individual disposable towel.
- Thoroughly clean and disinfect each teat end, paying particular care to the teat orifice, by scrubbing with a cotton swab soaked in 70 percent alcohol. Use a separate piece of cotton for each teat.
- Prepare teats on the far side of the udder first, followed by teats on the near side. (Teats may be cleaned and infused individually, if necessary.)
- Treat quarters in reverse order; near side first, far side last.
- Insert only the tip of the cannula into the teat end and express all of the contents. Do not allow the sterile cannula to touch anything prior to infusion.
- Do not massage the teats to disperse the product.
- Dip teats in an effective germicidal product after treatment.
- Identify treated cows and remove them from the milking herd to prevent antibiotics from entering the milk supply.
Drying off methods
Concentrate feeding of high-producing cows should be stopped two weeks before the anticipated drying off to reduce daily yield (target less than 35 lb or 15 kg per day). A change in environment can also help reduce production. Abrupt cessation of milking is recommended when the target daily yield has been achieved. Intermittent milking along with a decrease in the energy concentration of the ration can be used as a method to achieve the target yield. Cows should be observed closely for the first two weeks after drying off to ensure that udders are involuting properly. Udders with swollen quarters should be examined for mastitis.