It's nice to have some specific cut-points for determining a course of action. Researchers at Cornell University have come up with some for predicting metabolic disorders in fresh cows, decreased reproductive performance and lower milk production.
In a study involving 100 herds, researchers looked at the association between negative energy balance and the chances that an animal would develop clinical ketosis, displaced abomasums, metritis or retained placenta. They found that if non-esterified fatty acid (NEFA) levels are greater than or equal to 0.3 mEq/L in animals prepartum and greater than or equal to 0.6 mEq/L in animals post-partum, the animals have a significantly higher chance of developing metabolic disorders. For instance, if NEFAs exceed those levels post-partum, the animal is 9.7 times more likely to develop a displaced abomasum than if NEFAs are lower than that.
Animals with elevated NEFA levels are also more likely to have problems getting pregnant and make less milk. Likewise, when B-hydroxybutyrate (BHB) levels are excessive — greater than or equal to 10 mg/dl in post-partum animals — the animals are more likely to develop metabolic disorders, take longer to get pregnant and make less milk. Nutritionists can use these measures for troubleshooting purposes, Daryl Nydam, assistant professor of ambulatory and production medicine at the Cornell University College of Veterinary Medicine, told those attending the recent Cornell Nutrition Conference. He suggests taking blood samples from 12 to 15 animals in a herd, and if 15 percent or more of those animals have elevated NEFA or BHB levels, then it is a red flag. Perhaps the farm needs to make improvements in stocking density or cut down on the number of pen moves the animals are making.