September 2018
Feeding Facts

The Root of All Things Feed, Part 3: Fat

We have discussed two individual nutrients in some detail – protein and carbohydrates. Both are required to be on the tags when you purchase feed. They are listed as protein and crude fiber. The third nutrient that is required by law to be on a feed tag is fat, so it makes sense to me to go over that next.

Fat is one of the most often discussed nutrients in human nutrition, and most people have a clear opinion on fat and whether they want it in their diets or try to avoid it like the plague. In human nutrition, the discussion gets pretty deep, and fat sources and types of fats and oils are debated in great detail. Should it be saturated fats or unsaturated, or how much of each. What is the source of the fat? Etc. etc. etc. While these are important factors in human nutrition and are becoming widely discussed in pet foods, these finer details have not come to the front of the discussion in livestock nutrition yet, and generally, we will stick to the basics in this article.

Fats serve several purposes in the body, and we all (farm animals and humans both) have a need for a certain amount of fat. Fats serve as a carrier for fat soluble vitamins (Vitamins A, D and E) and are a significant source of energy in some diets. With that said, it is important to realize that there are over twice as many calories in a gram of fat as there is in a gram of carbohydrates. So, it is a much more concentrated source of energy and can add to weight gain much faster. That can be a good thing in a thin horse but not so much in a middle-aged nutritionist. The point is that fat is an important part of every diet but needs to be dealt with in a manner to add value and not create other issues.

When we look solely at livestock, we again break it down to monogastric animals (pigs, chickens and, in terms of fat digestion, horses can be shoved into this part of the discussion) and ruminants (cattle, sheep and goats). Monogastric animals can handle a significantly higher level of dietary fat than ruminants and while it is often an expensive source of calories, there are a number of times that it can be useful in feed for higher-producing animals. Most poultry feeds are not terribly high in fat and generally there is not a reason to really make higher fat feeds, unless it is a show bird that needs an extra shine to its feathers or a bird that is being exercised and conditioned for other reasons. In swine, there are a few instances where the extra calories are needed, such as a lactating sow with a large litter or a thin animal that needs to gain weight quickly.

On a side note, I would say that finishing swine feeds are one of the most critical places in animal agriculture to make sure the mixture of fat is correct. Fat is what gives meat flavor, and it is essential to have the correct mix to have a good flavored meat. The fat profile in the pig itself changes with whatever they are being fed and it is a fairly quick process. You can taste changes in three to six weeks and have a complete turn over in a few months. So strongly-favored fats like fish oil should be avoided at these stages. The ratio of saturated to unsaturated fats in a pig’s diet will also change the hardness of the fat and if the unsaturated fats make up too much of the diet, the fat will be soft and generally unacceptable to the consumer. Some grain byproducts such as Dried Distillers Grains can lead to this if fed heavily in the later stages of swine finishing.

In horses, three to four percent fat is a fairly normal level for general maintenance and in harder working horses we often see five to six or seven percent fat. With a horse’s relatively small stomach, a higher level of fat makes sense in many situations where more calories are needed. Fats will provide a tremendous amount of energy and take up less gut space and I have seen a newer trend to greatly increase the fat levels in some horse feeds. Fat levels as high as ten and twelve percent are becoming more popular and more available. I am sure that there are some horses that truly need a high level to maintain themselves in a hard-working environment, but before you transition your horse to one with that level I would recommend that you consult someone with a background in equine nutrition, and make sure that someone isn’t named Dr. Google.

Ruminants have a bit more trouble handling fatty diets, and while fats are a tremendous source of energy, they have to be limited in these feeds. Generally speaking, four to five percent of the diet is all that a ruminant can tolerate without causing problems. I am sure that there are exceptions, but none come to mind right now. Keep in mind that ruminants are designed to consume and break down carbohydrates and that whatever enters a ruminant’s stomach is usually broken down by the different bacteria in there. Few of those bacteria are particularly good at utilizing fats, and in most cases, high levels of fat coat the fiber that the majority of the bacteria feed on and make that fiber much less digestible. This, in turn, inhibits the energy production as a whole and makes the animal less efficient.

In summary, fats are important in all animals. Monogastric animals utilize them best and are much more flexible on the amounts that can be added. Ruminants need some fat but care must be taken not to overdo fat levels, and cause more problems than are fixed. Feed them where you need them, and keep in mind that if a little is good, a lot isn’t necessarily better.

 

Jimmy Parker is AFC’s animal nutritionist.