By ANN HINCH
Assistant Editor 

ST. LOUIS, Mo. — Access to fresh water provides one-sixth of the nutritional requirements for livestock. Grazing and manufactured animal feed are often juggled to provide the rest, including minerals, vitamins, fats, proteins and carbohydrates.

Animals do not have a requirement for crude protein by itself, according to Dr. Rob Payne, director of Nutrition and Technical Services for Evonik-Degussa Corp., North America – rather, they need the amino acids in crude proteins so the body can make its own protein. Payne was one of approximately 30 speakers at the Feed Industry Institute in St. Louis in June.

“From the quality point of view of building protein, we look at (feed) protein as the most important nutrient,” he explained.

Amino acids are made up chiefly of carbon, oxygen, hydrogen and nitrogen. “They have a very basic design,” Payne said of their molecular makeup. “All amino acids share the same structure.”
What differs is the R-group that attaches to the base molecule – these help make 22 amino acids, 20 of which are of interest for animal health. And of those 20, 10 are essential to be provided in the animal’s diet, meaning they can’t be naturally synthesized by the body.

Payne said final proteins aren’t just used for the muscle mass we all think is their chief end product – the meat we consume – they’re also important to growth hormones, insulin, disease antibodies, enzymes to break down food and keratin (for hooves, hair and skin).

There is a specific sequence to how amino acids link to create particular muscle masses. If the body lacks a certain acid, Payne said, this “chain-building” stops. Since the body cannot store amino acids for long, it needs a steady supply from food protein – and a balanced supply, since too much of any one component goes to waste. Unused carbon gets turned into energy or fat; nitrogen is urinated out.

“(Animals urinate) on the ground a very valuable protein source because we didn’t have an essential amino acid (to synthesize protein),” he said, adding as protein content increases, so do livestock ammonia emissions.

Amino acids rank in importance by type of livestock; that is, each animal has a greater need for particular quantities of some than for others. This is important for feed manufacturers to know, as well as the purpose of the animal being fed – meat? Milk? Eggs? Reproduction?

Also, the source of protein matters. Payne said blood meal has a high crude protein content, for example, but the quality may not be as high as protein in other feed components such as grain meal and oilseeds. The body has to be able to easily break food proteins down into amino acids or, again, those building blocks will go to fat or be burned as quick energy or waste.

Payne said it may surprise some to know, for example, that wheat has a better protein profile than corn, which is normally the preferred feedstock. Protein quality is also dependent on feed processing. Too much heat, for example, can make certain amino acids unavailable to an animal; others require a great deal of heat to unlock, such as when processing soybeans.

Carbohydrates

Anybody who’s been on a diet knows what a “carb” is, or at least thinks they do. As the name implies, carbohydrates contain carbon, hydrogen and oxygen, explained Dr. Kevin Halpin, vice president of Nutrition and Technical Services for IIC.

Grains such as corn, wheat, barley, oats and rye are 70-75 percent carbs and are used by the body primarily for energy. As a general rule, plant-based feed is higher in carbs and animal tissue-feed is higher in protein.

Glucose is the primary sugar found in the body from carbs. As a monosaccharide – one sugar unit – glucose is most easily absorbed by the body. Disaccharides (two units) such as lactose and polysaccharides (more) such as starch and cellulose require enzymes to break down for use by the body. Most carb sources are metabolized to glucose form, said Halpin.

Sugars, of course, are sweet. Different kinds of sugars are different kinds of sweet – a “milk sweet” isn’t the same as a “fruit sweet.” Sweet is an important taste to some livestock (and humans) and can make necessary food go down easier depending on the species – a chicken doesn’t care about a sweet taste, but calves and piglets have many more taste buds to please.

“The sweetness of our diets, in some cases, is pretty important,” Halpin explained, adding when weaning young pigs, lactose in the feed will make the transition off the teat into feed easier.

When it comes to ruminants such as cows, which can break down cellulose – carbs – far easier than non-ruminants such as pigs, he said the most challenging thing is to balance fibrous with non-fibrous feed. Fiber is needed to stimulate chewing and as a source of fuel to microbes in the animal’s digestive system.

“If the cow is just consuming a bunch of hay (which is cellulosic material), that rumen is going to fill up,” Halpin said; of course, too little fiber means rapid fermentation in the stomach and possible acidosis. However, “if we end up with too much carbohydrates in the diet, it’s stored as fat.”

Areas of research right now include observing the effect of lactose on gut health in livestock, alternatives to lactose for pigs and the role of simple sugars in cattle and swine health.