A smooth transition into the milking herd is essential for heifers’ success in the first lactation and beyond. One challenge that affects first-calf heifers more than older cows is udder edema. Heifers with edema retain fluids in the intracellular spaces of mammary tissue, leading to swelling of the udder and teats that sometimes extends into the abdomen. Tenderness and the distended shape of teats can interfere with milker attachment and milk letdown, and chapping of the teats can increase the risk of mastitis. Severe swelling can do permanent damage to the connective tissue that supports the udder.
University of Florida researchers reported that heifers that calved with edema had lower milk yields at their first test date than those with no edema. Milk production was not affected throughout the remainder of the first lactation. However, heifers that experienced edema in their first lactation were 1.62 times more likely to develop edema in the second lactation.
The exact causes of udder edema are not certain, although factors such as excessive sodium, potassium or energy intake and genetic predisposition have been suggested as potential causes. Over-conditioning of heifers should be avoided for numerous reasons, but it may also contribute to edema. Eliminate free-choice feeding of salt and buffers containing sodium or potassium during the last three weeks of gestation. Nutritional consultant Mary Beth de Ondarza recommends keeping sodium below 0.15 percent of the diet and potassium below 1.4 percent of the diet during the last three weeks before calving to avoid udder edema.
Research from the University of Tennessee suggests that oxidative stress may also contribute to udder edema. Mycotoxins and excessive iron and molybdenum react with oxygen to increase oxidation. Increasing antioxidants in the diet may help to limit oxidative stress. Tennessee researchers suggest feeding 1,000 IU/day vitamin E, 0.3 ppm selenium, 60 ppm zinc, 20 ppm copper, 60 ppm manganese and 0.25 percent magnesium before calving. They caution that environment, diet and disease can affect oxidation-reduction balance and that these levels are a starting point. Adjustments may be needed, depending on other factors affecting the situation.