Key Points for Disease Management in Late Dry Period of Dairy Cows
The late dry period refers to the period from the end of the early dry period to before calving. It is also commonly called the pre-periparturient period, that is, the 2 weeks before calving.
When cows approach calving in the pre-periparturient period, improper feeding and management can make them prone to various diseases. Therefore, feeding at this stage centers on health care.
In terms of feeding, this should be handled flexibly according to the cow's body condition and the degree of udder development and swelling. For cows that are too fat, concentrate should be reduced at this time, and the ration should be based mainly on high-quality hay. For cows in poor nutritional condition, concentrate should be increased immediately, but the maximum amount of concentrate should preferably not exceed 1% of body weight. Increasing the amount of concentrate fed before calving gradually adjusts the rumen microbial flora to adapt to a concentrate-feeding type, which helps the cow adapt quickly after calving to high milk yield and high-concentrate feeding, can maintain a strong appetite for concentrate, allows the cow to lactate fully and brings the lactation peak earlier, and reduces the incidence of ketosis. However, for cows with severe udder edema and subclinical mastitis before calving, it is not advisable to increase concentrate too much, so as to avoid aggravating udder engorgement or triggering mastitis. At the same time, for those with severe udder edema, salt feeding should also be reduced.
Research in recent years has shown that using a low-calcium feeding method 2 weeks before calving can effectively prevent the occurrence of postpartum paralysis, that is, reducing the calcium content of the general ration from 0.6% of dry matter to a low level of 0.2%. Because the normal blood calcium maintenance level of cattle is regulated by parathyroid hormone released by the parathyroid glands, when calcium supply in the ration is insufficient to maintain the normal blood calcium level of the cow, the parathyroid glands functionally strengthen regulation and will break down bone calcium from the cow's body to maintain blood calcium levels. Therefore, at calving, bone calcium is continuously transported into the blood, avoiding postpartum paralysis caused by the cow secreting large amounts of milk after calving and calcium being excreted in large amounts through the milk.
In the pre-periparturient period, the ration should reduce bulky succulent feed. At this time the fetus is enlarging and presses on and affects normal gastrointestinal motility, making constipation likely. The proportion of wheat bran in the concentrate should be appropriately increased, because wheat bran contains much magnesium and has a mild laxative effect, which can prevent constipation before calving. Daily supplemental feeding of vitamin A and vitamin D (or intramuscular injection) can improve the robustness level of newborn calves, increase the survival rate, and also reduce the occurrence of retained placenta and postpartum paralysis.
The focus of strengthened management in the pre-periparturient period is health care work, preventing infection of the reproductive tract and mammary gland as well as the occurrence of metabolic diseases. Cows should be moved into the maternity barn 7 days to 10 days before calving and cared for by specially assigned staff. Before moving the group, it is advisable to spray and disinfect the maternity barn with 2% caustic soda water, spread clean and dry bedding, and the maternity barn should establish and adhere to a daily cleaning and disinfection system. After the cow's hindquarters and limbs are washed and disinfected with 2% to 3% Lysol solution, they can be moved into the maternity barn, and the group-transfer record registration and handover work should be completed.
Inside the maternity barn, the cow beds should be kept clean and the bedding changed frequently. Prevent draft wind from striking the cow's body. In winter, warm water should be drunk, preferably at a water temperature of about 36°C; ice water must never be drunk and frozen or spoiled feed must never be fed, so as to avoid causing diarrhea and triggering premature birth. Observe changes in the udder every day. If there is excessive edema, especially the higher-yielding the cow the more severe the edema, diuretics may be appropriately administered to reduce the degree of edema. If the udder is found to be red and hard, under unavoidable circumstances milking may be carried out early, but the colostrum must be preserved well. When the weather is clear, the cows should be driven out of the maternity barn for free exercise. Never keep them shut in a damp cowshed all day, which is unfavorable to health and makes them susceptible to disease.