How much corn can I feed my goats?

Corn is safe for goats in small amounts. While corn is relatively low in protein (8% CP), it does contain a certain amount of calcium, which, in excess, can contribute to the onset of urinary calculi in bucks.
Although there is a tendency to feed corn because it is less expensive, never feed more than 50% of the total diet, except for heavily producing dairy goats. Adult meat goats should be fed a maximum of 1% of bodyweight in supplemental grain, with lactating does reaching a maximum of 1.5%.
Feeding an animal a large amount of concentrate (grain) causes acidosis, which results in a drop in rumen pH and a decrease in rumen motility. With acidosis, the animal usually will go off feed, have diarrhea, and show signs of depression for a couple of days. In severe cases, acidosis can cause death (Attra-Coffey, 2004).
Animals that are fed high-grain diets can also contract enterotoxemia, which is caused by epsilon toxin-producing Clostridium perfringens Type D (pulpy kidney disease). The symptoms of this disease are soft and pulpy kidneys, excess pericardial fluid, pulmonary edema, and hemorrhages on the serosal surfaces (Sheep and Goat Medicine, Pugh, 2002).