Many of you are starting to dry cows off at the moment so I felt a few words outlining the principles of dry cow therapy (DCT) might be appropriate. DCT is the treatment of sub clinical infection in the udder as diagnosed by the cow having an elevated somatic cell count. Sub clinical infection can be difficult to treat in lactating cows. The most efficient and effective way to treat such cases is at drying off. Reasons for DCT Curing existing cases of sub-clinical mastitis. Cows with sub clinical mastitis are a risk to healthy non infected udders by transfer of bacteria via the milking machine. Sub clinical infection can reduce potential milk production. Individual cows with high somatic cell counts contribute to the bulk SCC and can result in financial penalties. DCT reduces the chance of mastitis during the dry period and early into the next lactation. The management of cows prior to DCT and selection of correct animals for treatment is important and will determine its effectiveness. When cows are dried off a keratin plug forms in the teat and protects the udder from external infection. If this plug starts to form and is disrupted then it takes much longer to re-establish itself as an effective barrier. For this reason ensure cows are producing less than 10 litres daily before DCT otherwise the teat will remain open , drip milk and the keratin plug will not form. Cows should be milked once daily for a week prior to drying off and placed on maintenance rations. Every second day milking will cause continuous disruption of the keratin plug. Any cows with clinical mastitis should be treated with an appropriate lactating cow product and possibly injectable antibiotics before DCT is infused. The selection of cows for treatment is important and should be based on the level of infection in the udder. Any cow that has had a single SCC of >150,000 that season should be treated as should any heifer with a SCC of >120,000. Animals that have had a high SCC at drying off should be monitored at the beginning of the next lactation. If they are persistently high then culling these individuals should be considered. Any cows that have had clinical mastitis during the season should also be treated with a dry cow product. The teat end must be thoroughly cleaned and disinfected prior to infusion of DCT otherwise bacteria can be carried up into the udder on the nozzle of the dry cow tube and effectively sealed in (a recipe for disaster ). All teats should be sprayed with a suitable teat spray after infusion. Which Product To Use Several factors can influence the choice of DCT but a few basic rules should be followed. Which bacteria are present? It can be useful to take samples from a few high cell count cows and determine which bugs are present and the antibiotics they are sensitive to. Which product has been used as the main treatment during lactation? It makes sense to use a different class of antibiotic during the dry period. Eg. if a penicillin based product was used as the main therapy during lactation a cephalosporin, for example, could be used during the dry period. How long is the dry period? Short, medium and long acting preparations are available. What problems were encountered last season. Depending on whether your herd has cows with high individual SCCs; whether your herd had a number of clinical mastitis cases during the dry period, or through the calving period, will influence if you should use a long, medium, or short acting product. If you have any questions regarding DCT then please contact us at the clinic. There are a number of products available and the correct choice plus efficient use of product is important.