There are a good number of commercial sources of feed-grade lipids, being either fats (solid) or oils (liquid). With the exception of coconut fat (which is a vegetable oil in solid state), all vegetable lipids are oils, whereas animal lipids are fats. Hydrogenated oils are also solid, but this is a treated source of lipids, as opposed to more conventional ones, which are products of primary extraction. Nevertheless, lipid waste products are becoming increasingly available. In fact, there are so many varied products that selecting the right lipid source can be problematic.
This has to do not only with quality characteristics of each product itself but also with the interaction of each lipid with the animal and even other nutrients in the diet. First, young broilers are known for their slightly reduced efficiency to digest fats and oils, something that has been attributed to reduced bile production and/or efficiency, at least until a more reliable diagnosis is available. As a general rule of thumb, birds less than 10 days of age experience a 10 percent reduction in fat energy digestibility. In other words, energy specifications for fats should be reduced by 10 percent when formulating feeds for Phase 1 (post-hatch) broilers to account for this effect. To this end, it helps to use vegetable oils, as they are slightly more digestible than fats.
The following brief outline of common and less common sources of fats and oils used in broiler feeds provides but a primer in this very interesting, yet complex, aspect of nutrition.
1. Tallow and lard
They used to be the primary source of lipids in all poultry diets, but their use is declining as these are becoming less available and less desirable. Both are highly saturated fats that lead to firmer carcass fat consistency, but saturated fat is nowadays considered an undesirable fat from a human health point of view. As they are less digestible than vegetable fats, their use is more frequent in later phases.
2. Poultry fat
Monogastric animals, which include broilers, tend to deposit the same quality fat as the lipids they consume.
3. Corn and soybean oils
In fact, here we can group all oils derived from vegetable sources (except coconut fat, which is saturated, very expensive and seldom used in broiler feeding). Vegetable oils have better digestibility than animal fats, and they are the preferred source of lipids in Phase 1 diets, especially in super-dense prestarter diets that boost birds right after hatching. As mentioned, they reduce carcass fat handling characteristics, but their polyunsaturated fatty acid profile is considered more desirable — or less harmful — than that of saturated lipid sources. Purified oils (degummed) are even more useful, but they also come at a premium price.
This is the by-product remaining after oil refining. It is high in moisture, free fatty acids and it can be acidulated — all very undesirable traits for any lipid source as they promote rancidity, reduce digestibility and can cause equipment erosion, respectively. Their greater advantage is their low cost, and for this reason only they often find their way in the last diet before market age. With good quality control, soapstock can be a viable source of energy for broiler feeds.
5. Restaurant grease
This can be a mix of oils and fats, including overheated, burned and recycled lipids. Nowadays, it is mostly composed of vegetable oils as tallow and lard are no longer popular choices for fried dishes. Some restaurants use hydrogenated oils to protect them from overheating, and thus prolong their recycling time, but this is not deemed less ideal when their animal feeding value is concerned. Again, quality is of paramount importance for restaurant grease as a broiler ingredient as it can suffer from contaminants and residual foods, often burned.
Read more: Feed quality: Controlling lipid rancidity
6. Palm oil and coconut fat
Palm oil is highly saturated, whereas coconut fat is virtually fully saturated. Palm oil is inexpensive relative to coconut fat, and its use is widespread in broiler feeding. The opposite is true for coconut fat, not only because of its price, but also because of mixed results when fed to broilers. In general, palm oil is better suited for older birds. On the other hand, coconut fat might be suitable for younger broilers as its medium chain fatty acids, which abound in this lipid source, do not require the intervention of bile for efficient digestion. However, there is still limited research on the topic.
7. Animal-vegetable blends
Quite often, in this product, the worst lipid sources are mixed together to mask their undesirable traits. Likewise, it is possible to find blends of superb quality that can offer synergistic effects between the two major sources of lipids, and they do so at a very affordable price. The right blend of acceptable quality will offer enough saturates to keep carcass fat firm, less oil and less prone to oxidation — increasing its eye appeal and shelf life. In addition, a moderate level of unsaturated fatty acids will balance the undesirable profile of saturated fatty acids and offer a slightly better digestibility efficiency, especially for younger birds.
8. Designer lipid sources
Fish oil and flaxseed oil are usually too expensive to be used in normal broiler feeds, but they can be part of a niche broiler business aiming to market carcasses rich in omega-3 fatty acids. These fatty acids are also beneficial for the broilers as they promote a more robust immune system. Likewise, conjugated linoleic acid (CLA) has been shown to help against diabetes and cancer, and there are efforts to produce CLA-enriched eggs and CLA-rich broiler meat. These lipids have their own problems when it comes to feeding them to animals and require a different approach.
A very complex topic
This oversimplified primer on lipid sources for broiler feeds is just that: an introduction to a very complex topic that encompasses not only differences in origin or material, but also, and even more importantly, of quality — something touched here only very lightly. A high quality lipid source of the right type for the right feed will provide a strong performance advantage, whereas the opposite can be true: the wrong fat or oil can cause more damage than any initial savings from reduced feed cost.