Lessons From Predicting DDGS Quality, Part 1: Raw Observations
A recent publication on variation in DDGS quality, containing attempts to predict it with equations, has once again highlighted the inherent problems with using this ingredient to support animal performance. Distillers Dried Grains with Solubles, or DDGS, is a by-product of the expanding corn ethanol fuel industry. As a result, DDGS are plentiful and inexpensive; therefore, they are used in livestock diets. Typically, it is used to replace some of the corn, soybean meal and perhaps, phosphorus in a complete diet. This presents a challenge as DDGS is prone to variation in nutrient content and quality, a fact that has led to the development of prediction equations to determine the quality of each load. For reasons that will be discussed below, the energy content of DDGS can vary considerably and predicting the energy content of DDGS is important to support and maximize animal performance.
As the article stated, it’s important to outline how much variation exists. The authors obtained 15 DDGS samples from ethanol plants in the Midwestern USA, measured various nutrient levels and performed chick experiments to determine the metabolizable energy content (usable for productive purposes, like building chicken muscle for meat) – all to indicate quality.
The first figure depicts the amount of total (gross, or GE) energies in the 15 DDGS samples, along with the resulting metabolizable energies (AMEn) determined by feeding experiments. Gross energy simply measures the total heat (kilocalories) given off when the samples were burned, while metabolizable energy takes into account what happens when fed to the chicks.
As can be seen below, the GE values varied considerably in the DDGS samples. Also, the AMEn samples exhibited even more variation. Finally, and perhaps most striking, is how much lower AMEn values were then GE values. The authors state that the average AMEn value was 46% of GE – only 46% of the total energy in the DDGS was available for growth and productive purposes.
So, why was this so? In the next figure, data on several nutrients in the 15 DDGS samples is shown. As expected, the amounts of crude protein (CP), starch, fiber (NDF) and oil exhibited variation. For example, one sample had an ether extract (oil) value of 3.2%, while another had 13.2%. As oil is a form of concentrated energy, this would pose a problem for a poultry nutritionist balancing diets for maximum performance with the least cost.
So, to conclude, DDGS are abundant and cheap, but have tremendous variation in nutrient content and energy quality when fed to chicks. For proper diet formulation to maximize chicken meat production, testing and great care must be used to determine the value of each load of DDGS.
In Part 2, I will dive into the prediction-equation portion of this paper, highlight the difficulties encountered with developing the equation and examine what this says about DDGS use in livestock diets.