The debate about how to handle the dry period has existed for many years. A World War II, low feed inventory in the United Kingdom prompted dairy herds to implement the 60 day dry period. Currently, the practice is a 30 to 60 day dry period.
The 30 to 60 day dry period is based on physiological evidence that the mammary gland needs that time to break down and then redevelop. The mammary gland goes through three stages: active involution, steady state, and colostrogenesis. Throughout these stages the mammary epithelial cells (milk producing cells) undergo changes in cell morphology, where they become inactive (not producing milk) then become active and produce colostrum. While this has been proven to happen in the mammary gland there have been major changes in nutrition, management, and genetics of dairy cows that may lead to variations in how the dry period is handled.
Customized dry periods
While difficult to implement, recent research points toward the benefits of developing a customized dry period for individual cows. By customizing the dry period length there can be an improvement in the cow’s metabolic status, which can lead to a smoother transition from the dry period to early lactation. If the transition is easier, there is potential for a higher milk yield. Factors that should be considered when drying off a cow are milk yield, mastitis status, mastitis history, and if the cow is multiparous or primiparous. Cows that have higher milk yield at time of dry off have more potential for leakage and the teat ends being open and exposed to external bacteria. If cows need to be treated with antibiotics for mastitis, the producer should be aware of the withdrawal period to be followed. Primiparous cows appear to need a longer dry period than multiparous cows, possibly due to the nature of mammary epithelial cells at this point in the cow’s life. All these factors make it difficult to implement a customized dry period, especially on a large scale.
There has also been research conducted using continuous milking, skipping a dry period in between lactations. Continuous milking has the advantage of allowing the cows to remain in a better metabolic status via a higher planed ration that can be maintained through the next lactation. Some multiparous cows with little history of mastitis showed no impact on milk production in the next lactation. However, this was a limited group of cows and the research did not follow through to the next lactation after the study. Further research should indicate the impact over 2+ lactations and an economic cost evaluation for feeding a higher plane of nutrition in relation to milk production. Therefore, implementing a continuous milking protocol on the farm is a complex undertaking.
Much is expected from a cow during the dry period: she needs to maintain her body condition, maintain the growth of her calf, breakdown her mammary gland, redevelop her mammary gland, and produce colostrum. Until further research has been conducted, the best practices for producers are to maintain a clean and temperate environment for their dry cows, consult their nutritionist for appropriate rations, provide the appropriate dry cow therapy and supply ample water.