The Sunday News
IN the last instalment I mentioned various stages of lactation of a dairy cow and the need to manage these properly especially in relation to feeding. This week we focus on one of these stages and discuss how it is managed. This is the dry stage whose management is inextricably linked to both the preceding and succeeding stages. A dry cow is an animal whose milk production level has declined such that it is no longer viable to continue milking the cow. This is a stage which comes naturally in lactating cows as they approach final days of lactation. A dairy cow is normally in lactation (milking) for between 280 and 305 days with the peak milking period being recorded within the first 100 days of the early lactation stage especially around day 45 to day 50 of early lactation.
A dairy cow is dried at seven months of pregnancy or when the milk yield declines to about 10 kilogrammes a day for high yielders such as Holsteins. However, the drying off milk yields varies significantly with other breeds such as the red danes and jersey. It is therefore important for dairy farmers to keep accurate records of when their cows were serviced and became pregnant so that they can calculate the seven months of being in calf and start drying off their cows.
The dry period is necessary to allow the mammary gland to go through a normal period of repair and development and to ensure that the mammary cell numbers continue to multiply normally during early lactation. A short or absent dry period greatly reduces the number of secretory cells in the mammary gland and reduces milk yields. If a cow is not given an adequate dry period to rest the udder the subsequent lactations will have decreased milk yields. Also a cow which was not given enough time to dry off is highly predisposed to mastitis. The dry period should be between 60 to 65 days for adequate rest and regeneration of the mammary tissue.
The drying off period also allows for important management practices to be carried out. These include vaccinating your cows against a number of diseases. This is the ideal time to vaccinate the cows as they no longer have the milking stress and hence can easily handle the stress induced by vaccines into their system. Vaccination at the drying off stage produces protective antibodies for calving time and early lactation period. It also results in protective antibodies in colostrum for passive protection of the calf. Vaccines such as rotavirus which are introduced during the dry off period protects calves against scours which is a very common problem with many dairy farmers.
When drying off cows farmers should stop milking and change the feed type that is given to the cows. The feed is changed from dairy meal to dry cow meal. The dairy meal has a high crude protein (CP) content which ranges from 18 percent to14 percent depending on the stage of lactation of the cow. However the dry cow meal has between 10,5 percent to 11 percent CP and it is formulated so that it stops stimulating the cow to produce milk and prepares it for the next lactation.
Another critical factor in dry cow management is to keep the cows at an appropriate body condition score. Ideally cows should be dried off in condition score three and maintained at this condition score until calving. Dairy cows should not be too thin or too fat as each condition presents its own problems to the farmer. Over conditioning cows or fatness (body condition score greater than 3,5), may cause the cow to have difficulty at calving, be more susceptible to metabolic disorders and infections. While under condition or thinness (body condition score less than 2,5), in the dry cow can frequently lower milk production and reduced lactation period.
Finally farmers need to realise that a dry cow is given similar attention and management as a lactating cow. The tendency in most farmers is to neglect a dry cow because it is presumed to be out of production and hence not worthy the attention and resources but an improperly managed cow during the dry period will present challenges such as low milk yields in succeeding lactations, disorders such as milk fever and ketosis which are all costly to the farmer.
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