Part 2: Evaluating Ingredients in Poultry
In part 1, I discussed the effect of dietary crude fiber level, or the amount of indigestible carbohydrates, on metabolizable energy content of a broiler diet. As the level of dietary fiber increases, the amount of metabolizable energy, or that which can be used for growth and development, declines because poultry are not equipped with a digestive system that can accommodate much fiber.
So, when you’re evaluating ingredients, it’s important to have an understanding of nutrition and physiology to help guide your formulation program.
Dietary fats and oils are another major category that must be clearly understood. What’s well known is that fats and oils supply concentrated energy – about 2.25 times as much energy as the same amount of carbohydrates. It’s also almost always true that fats and oils are expensive.
So, since animal diets are formulated to contain a certain amount of energy, and other nutrients are pegged to this level, the addition of fat and/or oil – containing ingredients is very common. It’s easy to see why this is true when examining data from the same study that I referenced in part 1, which is shown below.
Graph depicting energy levels with fat intake
This is a clear relationship that is often exploited by nutritionists – adding a little dietary fat increases metabolizable energy in poultry. This is often used to meet the energy requirements for a particular stage of production. It’s also of interest that the gains in metabolizable energy with additional increases in dietary fat level eventually stop – shown above when fat level increases from 7.12 to 9.32%.
But, it’s important to remember that this relationship between fat level in the diet and metabolizable energy level is not always so clear cut. For example, the type and quality of fat or oil can have a big impact on the amount of metabolizable energy, as I’ve blogged about before, especially with younger poultry. In general, veg oils, like soybean oil, have higher metabolizable energy levels than animal fats.
It’s also important to consider using high-quality ingredients with residual oil, such as high shear dry extruded whole soybeans (extruded full-fat) and extruded/pressed (ExPress®) soy meal. These ingredients provide highly-digestible amino acids, in addition to ample available energy, in one package. In many cases, additional sources of energy, such as veg oils (which are expensive, as you recall), can be removed entirely, resulting in a less-expensive formulation that supports the same or greater level of performance.