**1. Introduction**

Ruminants have a valuable role in sustainable agricultural systems and provision of food to human beings. They play a pivotal role in converting vast renewable resources from rangeland, pasture, and crop residues and/or other by-products into food edible for humans. Grazing ruminant animals is an efficient way to produce food for humans. The need to maintain ruminants to utilize these humanly inedible foodstuffs and alter them into high-quality foods for human consumption has been a characteristic for several thousand years. In fact, dairy cattle and goats are quite exceptional in being extremely efficient in converting plantbased protein/energy sources into high-quality animal fats and proteins. It is convincing that ruminants are essential components in food production systems now and in the future.
