Farm406

Cows carrying large or multiple fetuses and those with health conditions such as lameness or disease are particularly susceptible, Stokka notes. Toxemia may occur in cows of all ages and at high levels within a herd due to widespread nutritional deficiencies. Both thin and fat cows can be affected, but it is more likely that toxemia will occur in over-conditioned cows losing significant amounts of body condition over several weeks. "When feeding straw, annual forages, or drought-affected forages, lack of energy is not our only concern," says Block. "An imbalanced mineral profile can also result in various metabolic disorders that result in down cows." Colostrum production begins around four to six weeks prior to calving, and high calcium levels are pulled from body stores into the udder. Even if calcium is adequate in the diet, absorption is limited, and the cows may not be able to mobilize bone calcium to meet increased metabolic demands. Although milk fever or hypocalcemia is generally associated with older, high-producing dairy cows, it can also occur in beef cale. Sudden decreases in calcium levels cause hyper- excitability of the nervous system and muscular weakness, lowered temperature, increased heart rate, and down cows. Other metabolic conditions can result in hypocalcemia, including excess phosphorus and low magnesium. In addition, conditions such as reproductive tract infections, injuries from calving, nerve or muscle damage, retained placenta, and prolapsed uterus are associated with milk fever. In addition to its association with milk fever, low magnesium can result in a tetany situation. Although most people think of tetany risks associated with rapidly growing spring forage, it can also occur during fall or winter when feeding harvested grass, alfalfa, or annual forages that are low in magnesium, says farm406 40 When considering nutrition requirements for cows and heifers, keep in mind that their requirements change depending on their stage of production.

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