Goats are ruminants and thus have a digestive system that includes a complex four-compartment stomach. This type of digestive system enables goats to utilize a wide variety of feedstuffs including grains, protein supplements, hay, silage, pasture, browse and non-protein nitrogen sources such as urea. The four compartments are the (1) rumen, (2) reticulum, (3) omasum and (4) abomasum.
The first two compartments, the rumen and reticulum are quite large with a capacity of 3 to 6 gallons. This is where the fermentation of feedstuffs consumed by goats takes place. The rumen and reticulum contain billions of bacteria and protozoa that partially digest the feed and allow the goat to utilize forages and browse for energy and protein. These microbes produce by-products in the form of volatile fatty acids (acetic, butyric & propionic) that the goat uses for energy, high quality microbial protein and B-vitamins that help meet the animal’s nutrient requirements. Further digestion and absorption of nutrients continues in the omasum. From the omasum, feed enters the abomasum or “true stomach” where digestion is similar to human’s, utilizing enzymes and hydrochloric acid for further breakdown of feeds. Food next passes into the small intestine where digestion continues with mechanical, chemical and enzymatic activity. The majority of sugars, amino acids, vitamins and minerals are absorbed in the small intestine. Ingesta passing out of the small intestine is watery – a major function of the large intestine is to reabsorb water. Remaining undigested feed, microbial cells, secretions and abraded tissues pass through the rectum and are excreted. This entire digestive process allows goats to utilize feeds, particularly high fiber roughages and browse, to produce meat, milk, and hair efficiently and competitively.
Though goats are ruminants and also herbivores (plant eaters), like sheep, cattle and deer, they do not eat the same types of plants. Cattle and sheep graze more grass and weeds, deer are more browsers eating leaves and buds from woody plants. Goats are classified as intermediate feeders because they eat a combination of grasses, browse and forbs. There are even differences in feeding behavior between goat breeds. Spanish breeds are more efficient browsers than Angora goats because they are taller and can reach higher browse and have less hair to get caught in branches. These different feeding behaviors affect animal performance and how and when goats should be fed supplemental feeds. Further, the type of production system (meat, milk or hair) and location of the enterprise dramatically effects nutrient requirements.