DRY COW THERAPY

Pashu Sandesh, 22^nd June 2018

Dr. Rajesh Kumar Singh

Introduction

Dry cow therapy (DCT) is the treatment of cow’s teats at the end of lactation with a long acting antibiotic preparation with or without a teat sealant. This is to treat for any intra-mammary infections (IMI) contracted during lactation and provides protection against new infections during the dry period. Using antibiotics at drying off is more successful at eliminating IMI than treatment during lactation since higher concentrations of antibiotic can be used. This is the rationale behind using an antibiotic at drying off.
DCT is useful to protect against new intra-mammary infections during the dry period which can lead to clinical or subclinical mastitis during the subsequent lactation. Most cases of clinical mastitis occur in the first few weeks after onset of lactation and it has been shown that over 50% of these infections originate from the dry period (Bradley and Green, 2000).

On cessation of milking at the end of lactation, the teat canal closes and forms a keratin seal. This process may take up to two weeks to complete and therefore presents a risk period for new IMIs to develop. The other main risk period is in the last couple of weeks before calving when the integrity of the teat canal seal is compromised as the udder prepares for the subsequent lactation. Providing protection against new intra-mammary infections is the rationale behind using a long acting antibiotic preparation at the time drying.

A problem may arise when using just long acting antibiotics for DCT as they may not provide sufficient protection alone for the whole dry period. This is because during the second risk period prior to calving, antibiotic levels may have reached low levels insufficient to confer protection against new IMI. This is the rationale behind using an internal teat sealant which prevents new IMI for a prolonged period of time.

Currently available internal teat sealants use an inert bismuth based paste, which is infused into the teat canal. This may be performed alone or after infusion of an antibiotic. If used alone, it is important to ensure that there is no pre-existing subclinical infection. A common problem with using teat sealants is their misapplication by farmers who introduce the paste in a similar way to a normal dry cow antibiotic. It is important that the paste resides within the teat canal only in order to be effective. This is effectively performed by pinching the top of the teat between two fingers of one hand while infusing with the other. Failure to do so will mean using the product will be ineffective in preventing new intra-mammary infections during the dry period.

External teat sealants

External teat sealants are in the form of a barrier film that is applied to the teat skin as a dip. Its duration of action is thought to be approximately 7 days. However, it is considered to be a less effective preventative of new infections during the dry period than the internal teat sealants and therefore is less widely used. The efficacy can be increased by regular application during the dry period although this is likely to be too inconvenient for the farmer to consider.

Administration

It is of extreme importance that DCT is administered aseptically. Before infusion, the cow should be milked out and each quarter thoroughly cleaned and disinfected. The cleaning process is aided by the use of a pre-milking teat dip. The furthest quarters away should be prepared first, followed by the near quarters. This is to prevent contamination of the prepared near teats by the operator leaning to reach the teats further away. For the same reason the near teats should be infused prior to those further away.

A partial insertion technique is recommended to try to minimize damage to the teat canal. Infusion may be followed by massaging the udder to aid dispersal of the antibiotic. Post-milking teat disinfection can then be applied. Throughout the process, the operator should be wearing clean disposable gloves. The cow should then be moved to a clean penned area for a minimum of 30 minutes to prevent them lying down and allow closure of the teat canal. The cows should then be moved to a specific dry cow group.

DR RAJESH KUMAR SINGH, JAMSHEDPUR, JHARKHAND, INDIA rajeshsinghvet@gmail.com