(Editor's note: This article was written by the NMC (formerly the National Mastitis Council) and originally appeared on eXtension.org.)
Traditional dry cow therapy is the use of intramammary antibiotic therapy immediately after the last milking of lactation. If products have a medicinal purpose or claim, they require approval by the appropriate regulatory authority (the Food and Drug Administration in the United States and European Medicines Evaluation Agency in Europe). Approved products applied by intramammary infusion at drying off can decrease the number of existing intramammary infections and/or prevent new infections during the early weeks of the dry period.
Use of dry cow treatment is one component of an effective mastitis control program that should also include: proper milking procedures using properly functioning milking equipment; dipping teats immediately after milking with a product known to be safe and effective; good udder hygiene between milkings; keeping accurate records of clinical mastitis and somatic cell counts on individual cows to assist in making management decisions; treating all clinical cases of mastitis promptly and appropriately; and culling cows with chronic mastitis.
Curing existing infections
The most effective time to treat subclinical udder infections is at drying off. Dry cow therapy has the following advantages over lactation therapy:
- The cure rate is higher than that achieved by treatment during lactation, particularly for Staphylococcus aureus.
- A much higher dose of antibiotic can be used safely.
- Retention time of the antibiotic in the udder is longer.
- Tissue damaged by mastitis may be regenerated before freshening.
- The risk of contaminating milk with drug residues is reduced when the milk withholding time after calving is properly observed.
Preventing new infections
The risk of new intramammary infection is greatest during the early and latter portions of the dry period. Most dry cow treatments provide sufficient protection after drying off so that:
- The frequency of new infections during the dry period is reduced
- The incidence of clinical mastitis at freshening may be reduced
Few products have extended activity for the entire dry period. Most have maximum activity in the first few weeks of the dry period, and activity declines as the dry period length increases. If they have extended activity, then particular care is needed to prevent drug residues in milk when calving occurs earlier than expected.