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Adding supplements to mature, dry forages

Heather Smith Thomas for Progressive Cattleman Published on 24 August 2018
Cows with lick tubs

In fall and winter, most native forages and tame pastures are low in protein (unless fall rains stimulated new growth).

Yet many stockmen extend grazing as long as possible because winter feeding is usually the most expensive part of raising cattle. Adding a protein supplement to mature, dry pastures is generally cheaper than feeding hay.

Adequate protein level in ruminant diets is crucial for optimal microbial growth and function. Rumen microbes are key to unlocking the complex carbohydrates present in dried standing forage. Without protein supplementation on dry pasture, the rumen cannot adequately digest low-quality forages.

Protein supplied with alfalfa hay, cake, blocks or tubs, or byproducts like distillers grains, can help improve digestion of low-quality forages.

Ken Olson, extension beef specialist at South Dakota State University, says the key number is 7 percent crude protein.

“Requirement for the cow, even for a mid-gestation dry cow whose calf is weaned, is a little higher than that, but we’re talking about meeting the requirement for rumen microbes so they can digest the forage. That’s our first need before we worry about the cow,” he says. If we meet requirements of the microbes, they provide for maintenance requirements of the cow.

“If protein level in forage falls below 7 percent, it limits microbial fermentation in the rumen; we can’t grow a large enough population of microbes to get the job done.” Digestion slows, food moves more slowly through the tract, the cow can’t eat as much, and it loses weight.

We need to know the protein level in the forage. “Cattle are selective grazers,” Olson adds. “If we clip a sample of forage, it may be poorer in protein content than what they are actually eating. We come closer in our estimate by observing what they are eating and hand-plucking a sample of similar plants.”

Many native cool-season grasses can be good fall and winter pasture without a protein supplement. They have more nutrients in their mature, dormant state than many tame grasses do.

Observing manure

“Two things I advise are to watch cow body condition and observe feces – how moist/fluid or dry they are. Cattle manure in the spring or on any lush green feed is very loose; manure is liquid. This is a sign of excess protein.” The material is digested quickly, traveling through the digestive tract too fast with some waste of nutrients.

“If manure is hard and makes a pile that stacks up, this is a sign of protein deficiency,” says Olson. There’s not enough to digest forage efficiently and keep things moving through at a proper pace. Ideally, manure would be moist and loose – but not liquid. This is how it would generally be when forage is still green but not so lush and washy; protein level is about where it should be.

“As forage goes into complete dormancy, we need to provide a supplement, but it’s amazing how well cattle do when you first put them into a new ungrazed dormant pasture,” Olson says. “They select a diet high enough in protein they don’t need a supplement, but the longer they stay in that pasture, the less protein they’re getting.”

“Young animals need more protein because they have a growth requirement, whereas the mature dry cow just needs to maintain itself. Youngstock are not full-size; their rumen is not yet fully developed, they can’t hold as much feed, and their ability to ferment large enough amounts of low-quality forages is less,” says Olson.

“This can be partially addressed with grazing management. Let them graze a pasture first and get the best material to meet their higher requirement and let cows clean up after them. The cows may need a protein supplement because the forage that would have allowed them to meet requirements of the rumen microbes has probably already been taken by the youngstock,” he explains.

Serving up more protein

David Bohnert, beef extension specialist and ruminant nutritionist at Oregon State University, says once you know to provide more protein, you must next ask: What are you going to use? How will you feed it? “It might be alfalfa hay, a feed mix in a feedbunk or a block or tub. It may depend on whether we can drive to those cows with a feed truck or tractor,” says Bohnert. In rough terrain, the best option may be blocks or tubs that can be hauled with a four-wheeler.

In a pasture you can get to with a tractor or truck to feed alfalfa, this may be a feasible solution since it doesn’t need to be fed every day. “You can feed every second or third day or twice a week. Feeding a supplement like cottonseed cake or cubes can even be done once a week with acceptable results.

Ruminants can recycle nitrogen when eating low-quality forage. If you provide a high-protein meal (cottonseed cake or high-quality alfalfa), they recycle a portion of it back to the rumen to keep the microbes functioning optimally for digesting the low-quality forage,” he explains.

“Historically, I think this is how ruminants evolved, to take advantage of periods they had access to higher-quality proteins, when ordinarily all they could find to eat was low in protein,” says Bohnert. They could consume higher-quality forages when they found them and utilize the protein over a longer period (two to seven days) until they found something else to eat higher in protein again.

“We can take advantage of that, and save labor and fuel, feeding a supplement like alfalfa or cake once or twice a week versus every day. This can be logistically difficult in some situations, however, and that’s where blocks, tubs or lick tanks are useful,” he says.

There are many kinds of supplements and nitrogen sources. “It boils down to what is economical and available (without a lot of freight cost), and how you plan to feed it,” says Bohnert. “Blocks or tubs can help affect where cattle graze – enticing them into areas/terrain they might not use otherwise.

Some extensive pastures are only 50 percent utilized by cattle. Providing protein will also help them utilize/digest that forage.”

Olson says lick tubs can work if cattle don’t overeat or undereat. “With youngstock, it can be a challenge to get them to use tubs. They may not consume enough, whereas some of the older cows will stay and eat from the tubs and won’t go graze.”

You may have to put multiple tubs at each site so several cattle can use them at once. Otherwise, dominant older cows may consume most of the protein and keep the more timid ones away.  end mark

PHOTO: In rough terrain, cattle are often given lick tubs that can be hauled with a four-wheeler. But multiple tubs at each site are best so dominant cows won’t consume more than their share. Photo provided by Heather Thomas.

ILLUSTRATION: Illustration by Corey Lewis.

Heather Thomas is a freelance writer based in Idaho.

What will it cost?

To determine your best buy regarding protein options, convert cost per ton of feed to cost per ton of protein that’s in the feed. “This requires a little arithmetic,” says Olson. “First, convert cost of feed to the cost on a dry-matter basis. Let’s say it’s alfalfa hay and 90 percent dry matter.

Use the price of the alfalfa (and to simplify, let’s say it cost $100 per ton, though it will probably be more), divide it by 0.9, and you have the cost of the hay on a dry-matter basis – about $111. Let’s say it is 17 percent crude protein. Take $111 and divide by 0.17 ($653.60). That’s the cost per ton for actual protein from that alfalfa hay,” he explains.

Note pad

“Then let’s say you could get dried distillers grains for $150 per ton. It might be 0.9 dry matter content ($167 per ton of dry matter) and, if it’s 30 percent crude protein (typical for dried distillers), that’s $555 per ton of protein. Those are not realistic prices, but you can use this formula to determine cost per ton of protein and compare different sources.

In this example, the alfalfa was about $650 per ton of protein, and the distillers was $555. Though the distillers cost a lot more per ton of product, it’s actually cheaper per ton of protein because it has twice as much protein,” Olson says. Then look at cost of freight and delivery, and what it will cost to take it to the cattle.

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