Dry Cow Therapy: What’s to consider?
In recent years dry periods have ranged from two months to nearly five months but from now on most cows will probably be dry for only six to eight weeks.
There are two potential issues with a shorter dry period.
- Bulk tank antibiotic residue failures with long acting dry cow tubes
- Less effective cure of sub-clinically (high cell count) infected cows.
The dry period is an important time for the cow to rest and recover from the previous lactation. Nutritionally it is an opportunity for the cow’s body condition to be managed so that she calves down with a body condition score of 3.00 to 3.25 (scale 1 to 5).
Too thin and she will not milk as well in the next lactation and be less likely to go back in calf on time. Too fat and the cow is at risk of a number of costly metabolic diseases including milk fever, abomasal displacement, metritis etc. all possibly leading to poor fertility later in the lactation.
For the udder, the dry period is both a period of risk and an opportunity to clear up existing infections.
Antibiotic dry cow therapy has two main objectives:
- To prevent new infections occurring during the dry period.
- To clear up existing sub-clinical infections.
Once a cow is dry for a couple of weeks and the udder has involuted (shrunk back), inhibitory substances, like lactoferrins and immunoglobulins are naturally produced in the udder tissue that further help eliminate underlying infections and prevent new infections from colonising the udder tissue. The cow also produces a waxy keratin plug that blocks the teat canal producing a physical barrier against the entry of new infections.
Risk of infection & relative persistence of different Antibiotics