What percent of body weight does a goat eat in grass per day?

The short, textbook answer is 4 1/2 percent body weight. But in reality is depends on many factors.

a mature goat can eat upwards of 10 gallons of rough forage per day.This is a large amount, and constitutes the higher end of possible intake of low quality (mostly insoluble fiber) food. Grass is such a food.

Grass is not optimum feed for goats. Their digestive tract is more honed for succulent leafy greens. Although they can eat grass, depending on what you are expecting them to do, they'll eat different amounts and need more nutritious feed.

In terms of grass, a goat could easily eat 4.5 percent of its bodyweight in grass everyday if the weather is fair it wasn't doing anything but maintaining its body weight. But this depends on the nutritional and caloric content of the feed, and the basic requirements of the goat.

a pregnant goat that is being milked through a cold winter can require more than 3 times the amount of calories than a non pregnant, non milking doe in the summer time. If the milking doe was just eating 4.5% body weight of grass, it would soon die.

A goat should not eat more than 8 percent its body weight in feed. In most cases it won;t even eat that much. the caloric content of that. A balance must be found depending on what is expected of the goat.