Hey thanks for taking an interest; I thought you would think I was looney for doing it, but because farming is a business, it actually is important.
To answer your question; there are a lot of inputs, like feed rations which can be a blend of hay, corn silage, grass silage, grain and minerals. That is what a sheep farmer is really looking for; what is the least costly to put in and get the most out of in 30 days, 60 days, 120 days, etc. A few years ago I tried this and had the lambs on a high protein diet and was getting amazing weight gains, but then my most prolific lambs started dying...and I mean 40 of them in a short amount of time. I blamed the intensive mix but it was actually a bacteria in the soil that was keeping their livers from growing as fast as their bodies; toxins built up in the liver from lack of size and were killing them, but now that I vaccinate them for that, I could try that again with better results.
Temperature would have a huge affect upon sheep because sheep are really furnaces themselves; the colder the weather they more they have to eat, but like a coal stove, there is no bottom to them; it is impossible to get a sheep too cold as long as it has feed in front of it to keep its belly warm, they are content. (Their ideal temperature is 20 degrees just as ours is 70 degrees.)
Other inputs are time, which means a lot to me. Anything I can do to save me dealing with sheep has huge savings when I compare what my labor rate would be. Like this year, I have put in about 10k worth of time based on a labor rate of $12.50 per hour (the MDOT rate for semi-skilled laborers). Now I can compare that with how much food I am producing for myself, and how much profit the farm operation is generating to decide if it is worth it.
One surprising area is the wood lot. It actually is a very bad performer. There are low imputs, but because a tree averages 40 years to grow before harvest, and property taxes are high, it is far better to clear the land and raise sheep on a given acre then grow forest products. It is one of the reasons why I am continuing to clear land; there is a lot more money in raising sheep than growing trees. A simple return on investment shows that.
This could actually play out into real world money elsewhere. There is something called SARE Grants which enable farmers like myself to do research for the benefit of other farmers. As I mentioned, sheep are hardy and actually do not need a barn, that is...barns are for the comfort of the farmer and not the sheep. I was thinking about how adding some thoughtfully arranged hedges that could keep the sheep out of the weather without significant cost. With half the flock under "green" living barns, and the other half out in the weather as a control, with the aid of weather measuring instruments like wind chill, wind speed, temperature, precipitation, etc, you could calculate out how much better off the sheep in the green living barns were compared to the sheep outside. Obviously the more comfortable they are, without significant cost, the sheep will go through less feed and save the farmer money while still retaining profitability with significant weight gain. You get a grant to help pay for the weather instruments and then carefully come to a deduction on different methods of farming.
Others may laugh, but I know some dairy farmers who do this sort of stuff, and keep amazing spreadsheets on their cows and it adds up to very profitable farming. It is pretty simple; if you do not track it, you are just guessing, and money can be saved with information whether it be cows, coal or sheep!