What Does Dry Cow Do?
The 2 main functions of Dry Cow Therapy (DCT) are- To cure existing subclinical mastitis infections.
- To reduce the number of new infections in the dry period and around calving.
How does Dry Cow Therapy work to cure existing infections?
DCT involves infusing an antibiotic preparation into the udder which stays in the udder after drying off.
It is known that cure rates of mastitis infections are increased when a high dose of antibiotic is maintained in the udder for an extended period of time.
Does DCT cure all cows?
No.
How can I tell if a cow is likely to be cured with DCT?
Factors that affect the likeliehood of cure are:
- Age. Younger cows have a higher cure rate than older cows.
- Number of quarters infected. Cows with 1 infected quarter are more likely to be cured than cows with 2 or more infected quarters.
- History:
- Cows that have had 3 or more clinical cases are less likely to be cured
- Cows that had a high ICCC last lactation, were treated with DCT and have a high ICCC this lactation, are unlikely to be cured.
- Type of bacteria: Streps are easier to cure than Staphs.
- Udder scarring: Examination of udders will find some cows with lumps and internal scar tissue from repeated infections. These cows have a reduced chance of responding to DCT.
For example:
- A 1st calver that had 1 clinical case and is infected with Strep. agalactia will have close to 100% cure rate.
- A 4 year old cow that had 1 clinical case and developed a high ICCC towards the end of lactation with Staph Aureus will have a 50-80% chance of being cured.
- A 10 year old cow that had 3 clinical cases in 2 quarters, had a high ICCC last year, has an uneven udder with some palpable scar tissue in the back left and is infected with Staph Aureus, has a less than 5% chance of being cured, even if she does give 45 litres!
Does DCT prevent mastitis?
We know that one of the high risk periods for cows becoming infected is during the dry period, especially just after drying off and just round calving. DCT at drying off will reduce the number of these new infections that occur during the dry period. Depending on the type of product used and the length of time the cow is dry, it will also reduce the number of new infections around calving.
It is important to note that DCT will not prevent infections by the types of environmental bacteria that may be introduced into the udder when infusing the DCT.
How do I know that a cow is infected with subclinical mastitis?
Mastitis is caused by bacteria entering the udder. We can determine this by culturing a sample of the milk. Culturing, while an important tool for investigating mastitis in herds, is impractical as a whole herd test. Individual Cow Cell Counts (ICCC's) are considered the best method available to determine whether cows have subclinical mastitis.
A cow is considered to have a subclinical infection if she has had an ICCC above 250 000 cells /mL at any time during her current lactation. At least 4 ICCC's are required to be confident of a cows status.
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