There is a wealth of knowledge out there that is available to anyone for free.
You can keep it simple or you can make it just as complicated as you want.
Ours is/was a pretty simple operation. We never fed bulls that were being offered for sale at some point, so my comments are not directed to the bull producer. We only fed hay and mineral to cows and heifers. Even doing just that we had our hay tested, knew what a cows requirements were and how that changed with temperature. Since our operation was fairly small as far as Se Montana ranches go, we bought a hay processor with a scale underneath so we knew exactly how much hay we were feeding per head per day.The add-on price of the scale was $2500. We figured we could pay for the scale by saving 50 ton of hay valued at $50/ton over the life of the machine. It well exceeded that.
We ran our 'ration' ourselves (based on analysis of hay and requirements of cows) and got by excellent. A rancher can't afford to under-feed and they can't afford to over-feed. It's a balancing act. Us, Mr. FH would rather over-feed as under-feed.

Some years you have to meet the basic requirements and nothing more, as mrj pointed out.
No one likes to see their cows walking and bawling because they are unhappy; but no one likes to sell their cows only to have to buy back cattle in ensuing years either. A man's gotta do what a mans gotta do. Of course you can't starve a profit out of a cow; but that's not what we are talking about here. What we are talking about is meeting their basic requirements.
Protein has been oversold for years. Feed stores make money selling protein and they are good at it.
We have found that 10% protein grass hay is enough for a range cow with no other protein supplement as long as they get enough of it.( Please understand, that is when feeding hay; cattle grazing grass in the winter need protein supplement.) The amount of TDN is important as well. The more north you get, the more important it becomes.
One needs to watch the ADF of the hay too, as that shows how digestible the hay is. I've seen poor hay being fed to cows that wasn't very digestible, so some was left on the ground. The rancher goes out to feed the next day and sees all the hay left over. His thought was the cows didn't consume all of the hay because they were being overfed, so he cuts them back on the hay. Over time the cows get thinner and thinner. That used to happen a more than it does now~ I think because of the tools that are available so that one knows more about the hay they are feeding. Ranchers that are interested have access to learning as much as they want to know.
The best bang for your buck is to GET YOUR FEED TESTED. You can't manage what you can't measure. A feed analysis measures what is in your feedstuffs.
Back to a the bulls. I've seen bulls at the different bull shows that a nutritionist had figured the ration for--those bulls were so dirty behind that
you knew something was wrong. Whether the bulls had been stepped up on ration too fast or the feed was too rich--who knows? Their behinds should
not be dirty when the ration is right for them to digest properly
Dirty behinds mean acidosis. Acidosis means the rumen isn't able to work properly and digestion is hampered. Regardless of who or what, we must remember we aren't feeding cattle, we are feeding the rumen.
Many (most) cattlemen can tell through experience, how their cows are doing on what they are being fed. Only problem with that is it takes 80 lbs to change a condition score on a cow. When fed improperly, they will lose 80 lbs. faster than they can put it back on during the winter. When you feed them every day, see them every day they can go downhill before your realize what you are doing isn't working. .(Not always, but sometimes.) When you know the requirements of a cow and know what is in your hay, you have a good opportunity to head off that weight loss. A real good practice is to get them into a body score of 6 going into the winter. Then losing 80# isn't a huge deal.
Starting at a 6 body score, a cow can lose one body score (80#) and still come into calving in a body score of 5, which is fine. Research shows if you start out with a body score of 5 and lose one body score by calving time,(drops to a 4) then that isn't a good thing. Even colostrum quality goes down. Starting the winter with a body score of 5 or less means bred cattle need to GAIN weight during the winter to be a 5 at calving. I don't know about where you live, but here it's very expensive to try to get cattle to gain weight during the winter. Your feed costs will soar. A cow won't gain weight easily on hay alone until she is turned out on grass in the spring. That's in our area...
This has been a good topic. Great discussion going on here, IMO.
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Denny said:
'Vigortone will whip up a ration for you if you give them your feed anallisis using your feed on hand and adding to it where needed.'
That's a correct statement. Denny. Thanks for bringing it up. I like the 'using your feed on hand part' especially well.
Not only will they run rations at no cost to you, they will take some grass and hay samples for customers free of charge as well. I am sure other companies offer that service, too. Not all, but some.