Every year at this time the grazing lists are buzzing with talk about how best to feed animals over-winter. The graziers want to be all grass all the time and get the best product, but reality rears its ugly head and they have to compromise their principles. Usually I just listen and do my talking here: the folks on the list are either master graziers that I should listen to, or novices that have nothing useful to say. I broke down and spoke up today, which may cause a flame war. I said:

Do the animals need to stay in top condition over the winter? If you have a dairy and have to fill the milk tank every day then you must feed them, but beefs are different.

Gestating beef cows only need 1/3 the feed of a lactating cow, and can live off back fat to some extent for a while with no harm to the fetus. Steers and heifers can stall in the winter but have a one-time burst of growth in spring when feed is plentiful, and finish on time despite a lean winter.

It's a fine line to walk, but you do have options to get through winter that don't require so much or such high energy imported forage, and that saves money as well as being better for animal health, all things considered.

Setting up to operate this way takes planning. Having cows in the second or third trimester of gestation at that time, and calves weaned and well started but not close to finish, takes management. If you aren't there yet or can't get there then you have to feed them.

As noted by others the health benefits of balanced fat (n6:n3) and CLA are not perfectly clear. Many studies are animal studies rather than human, or are short term and ambiguous, but the evidence is accumulating that the anti-inflammatory effects are significant for humans, and there is reason to be concerned since they're found in the highest concentrations in all the most active tissues: brains, eyes, hearts and even the tails of sperm. You can only get them from diet. What you eat you are. (Actually, there is evidence from epigenetics that you are what your mother and grandmother ate too, since DNA methylation changes expression in heritable ways.)

In general, both come from green leaves. There is some evidence that even hay is deficient. Once the greens wilt they are less nutritious. Unless you live where you can graze 24/7/365 then this is an issue that you just have to deal with. Perfection isn't on.

I don't feed grain, but I will feed some junk hay (oats, put up wrong with weeds in it) and some packing house trash (raisin stems with a few raisins clinging to them). My tests show that this method produces beef that has better than typical n6:n3 ratios. Your local conditions will probably require different specific steps, but I think that the principles are general and that you can find some combination of timing and supplementation that works for you and makes good beef. Test it and see.

This is a bit off topic to your question but I suggest that if you do import forage that you feed it on pasture so that the nutrients and organic matter plop on the pasture and so improve it. You are not only importing feed, you are importing fertilizer. In this way next year may be better than this one and yield increasing returns over time. If you are currently buying fertilizer then you might run the numbers to see if your bottom line can be improved by buying forage rather than fertilizer since you get a double benefit. You spend the money one way or another, so look for the best deal, all things considered.