Deciding what and how to feed sheep isn't complicated once you review sheep nutritional needs and consider the best available ways to meet them. As ruminants---animals with multiple stomachs, and the ability to extract maximum food value from their diets---the quantity of protein consumed is generally more important than the quality, but avoid feeding spoiled feeds to protect the rumen. Preparing feed rations for a handful of sheep or a small flock is fairly simple. The process gets much more complicated for vast numbers of sheep.
Offer free access to forage (pasture) as your feeding foundation, given that grass is the most natural feed for sheep, though the quality (food value) of your pasture is critically important. These factors are usually couched in terms of available crude protein (CP) and total digestible nutrients (TDN); ask an agricultural adviser to evaluate them. Seasonal or other declines in pasture quality can be overcome with hay and grain supplements.
Supplement pasture as needed with hay or silage, which is fermented forage stored moist or dry. Hay is more practical---and available---for most backyard farmers. For feeder lambs, feed 0.907 Kilogram of hay per head per day. For ewes and rams, feed 1.36 Kilogram per head per day for smaller breeds, 2.27 Kilogram for large breeds. If using processed hay cubes, feed as directed.
Supplement forage and hay with grain as needed. For feeder lambs provide 1/2 pound of mixed grain per head per day for maintenance and from 1 to 2 1/2 pounds daily for finishing. Feed 1/3 pound per head per day to maintain rams and ewes, more during breeding season, pregnancy and lactation. Add molasses for lambs, to sweeten the deal, or to otherwise add calories when they're most needed.
Add trace minerals, either as freestanding free-choice salt and mineral blocks (available at any feedstore) or as a loose fine supplement mixed with grain and molasses.
Fine-tune your feed mixes, develop an understanding of relative nutritional values and consider viable feeding alternatives with help from Montana State University's free online Sheep Ration Program. Various feed options may be more cost-effective in your area, for example, if extended drought or other circumstances mean pasture is scarce and hay too pricey.
Make sure fresh water is freely available at all times. Good green colour in pasture and hay helps guarantee adequate consumption of Vitamin A, an essential nutrient. Carrots and carrot tops are nutritious treats, and can be mixed into feed rations. For large flocks and feedlots, consider total mixed ration (TMR) mixers that grind together and uniformly mix livestock rations.