Location: Livestock Nutrient Management Research2012 Annual Report
1a. Objectives (from AD-416):
Obj. 1: Evaluate the impact of feeding low-fat dried distiller's grains (DDG) on dietary net energy and methane production. Technology is being adopted within ethanol plants to extract the germ, thereby reducing the fat remaining in the DDG. The removal of fat during ethanol production will most certainly reduce the energy value of the DDG. The impacts on dietary energy need to be defined before these products enter the marketplace. We have access to a limited amount of low-fat, medium-fat, and high-fat DDG. Calorimetry allows for NEm and NEg values to be defined with limited amount of product. Increasing dietary fiber also has the potential to increase endogenous methane production due to a changing microbial population. Our team has the ability to define both. Obj. 2: Determine the effects of treating distiller's grains with buffered enzymes on digestion and net energy content of the distiller's grains. Improving the digestibility of the fiber in wet distiller's grains plus solubles (WDGS) would improve animal performance. In lab-scaled systems, treatment with buffered enzymes increased DDG digestibility.
1b. Approach (from AD-416):
Exp. 1. Determination of net energy values and enteric methane production via indirect calorimetry. Dietary treatments will include low-fat, medium-fat, and high-fat DDG included at 30% of the diet compared to a steam-flaked corn-based control containing no DDG. Eight steers will be trained to the calorimetry system. Four steers will be fed ad-libitum and four will be limit-fed at maintenance in order to calculate NEm and NEg. Each steer will receive each diet in a Latin Square design. The indirect respiration calorimetry system used will consist of four chambers constructed of a metal pipe frame and Lexan sheets. Air will be analyzed for oxygen, carbon dioxide, and methane. Heat production will be calculated from oxygen consumption, carbon dioxide and methane production, and urinary nitrogen (N) excretion using the equation of Brouwer (1965). Each of the periods of the Latin square will consist of an initial 14-d diet adaptation and 7 d of fecal, urine, and gas exchange collections. Urine and feces from each steer will be weighed daily to determine total tract digestibility. Exp. 2: An individual steer finishing study will be conducted using Calan headgates. Three treatments will be used to determine the effects of treating sorghum WDGS with buffered enzymes on animal performance and carcass characteristics. The treatments will include a finishing diet containing 45% sorghum WDGS, 45% sorghum WDGS treated with enzyme, and 45% WDGS with 10% added limestone (to raise pH), then treated with enzyme. There will be 54 steers and 3 treatments (18 steers per treatment). Steers will be fed for 150 to 200 days.
3. Progress Report:
This agreement consists of two experiments. Experiment 1 is complete. Experiment 2 will take place in spring 2013. A major byproduct of the grain bio-ethanol industry is distiller's grains (DGS). Typically, distiller's grains contain approximately 10% fat. However, in the past few years many ethanol producers have started extracting oil from the DGS to sell for biodiesel production and other purposes. Therefore, the potential changes in the energy and feeding values of DGS has become a point of interest among nutritionists. Therefore, the objective of Experiment 1 was to determine the impact of feeding low-fat dried distiller's grains with solubles (DDGS) on energy metabolism and enteric methane production in cattle. We hypothesized that removing the fat from DDGS would decrease the energy value and increase enteric methane production. Four steers were fed one of four diets in four periods so that each steer received each diet for 14 days. The four dietary treatments consisted of a control diet with 79.0% steam-flaked corn and three experimental diets containing 30% of a low-, medium- or high-lipid DDGS to replace the steam-flaked corn, cottonseed meal and urea. The DDGS was obtained from POET Nutrition in Sioux Falls, SD. The fat concentrations were 5.54%, 8.40%, and 12.46% for the low-lipid, medium-lipid and high-lipid DDGS, respectively. Because of low feed intakes, animals lost body weight and had negative energy retentions and high heat production. Thus, the net energy values of the DDGS could not be determined for each of the treatments. Respiratory quotients (ratio of carbon dioxide production to oxygen consumption) allow estimates of nutrient oxidation while in the chambers. With ad libitum intake, the respiratory quotient was normal for the cattle fed the control steam -laked corn-based diet suggesting carbohydrate were being metabolized. However, the respiratory quotient of cattle fed the DDGS diets suggested that there was also fat oxidation along with the carbohydrate oxidation. The daily energy losses were similar for cattle fed the control steam-flaked corn-based diet and the DDGS diets, therefore, no conclusions can be drawn. The best estimate of the true energy value of each diet in this study was the metabolizable energy (ME) as a percentage of gross energy (GE) intake. Metabolizable energy as a percentage of GE was significantly greater (P = 0.03) for the control steam-flaked corn-based diet than the DDGS diets and decreased quadratically as the lipid concentration in the DDGS diets decreased. These results indicate that reducing the fat content in DDGS also reduces the energy density.