Which of the following is a method to prevent milk fever in cows?

To prevent milk fever in cows, feeding low-potassium hay and/or silage is an effective method. Milk fever, or hypocalcemia, typically occurs around the time of calving when a cow's calcium needs increase rapidly due to lactation. High levels of potassium in the diet can interfere with calcium metabolism, potentially leading to an increased risk of milk fever. By providing low-potassium forage, the risk of milk fever can be mitigated, as it helps regulate the balance of minerals in the body and stimulates the cow to manage its calcium levels more effectively.

On the other hand, increasing potassium in the diet can actually heighten the risk of milk fever due to its negative effects on calcium absorption. Administering calcium supplements before calving could also be counterproductive; while it might seem beneficial, this method can suppress the cow's natural ability to mobilize calcium from its bones. Reducing feed intake prior to calving is generally not advisable either, as it may lead to inadequate energy and nutrient reserves that are vital for lactation. Feeding low-potassium hay and/or silage, therefore, stands out as a practical approach to help prevent milk fever in dairy cows.