Location: Livestock Nutrient Management Research2013 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. Exp. 3. To cooperate with USDA-ARS in conducting respiration calorimetry studies on 1) the use of enzyme treated distillers grains on energy metabolism and enteric methane emissions of steers fed finishing diets, 2) effect of degree of steam flaking (24 or 28 lb/bu) and dietary distillers grain concentration (0, 15 or 30%) on energy metabolism and enteric methane production of finishing calves, and 3) effects of supplementation strategies on energy retention and enteric methane production of steers fed high forage diets.
3. Progress Report:
This agreement consists of two experiments. Experiment 1 is complete. Experiment 2 will take place in spring 2013. The energy value of the fat in dried distiller's grain with solubles (DDGS) has become a point of concern because ethanol producers have begun extracting oil from the distiller's grains and selling it for biodiesel production and other purposes. Therefore, the objective of Experiment 1 was to determine the impact of feeding low-fat DDGS on energy metabolism and methane production in beef cattle. We hypothesized that removing the fat from DDGS would decrease its energy value. 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 were a control diet with 79.0% steam-flaked corn and three experimental diets containing 30% of a low-, medium-, or high-fat DDGS to replace the SFC, cottonseed meal, and urea. The DDGS was obtained from POET Nutrition in Sioux Falls, SD. The fat concentrations of the DDGS were 5.54%, 8.40%, and 12.46% for the low-fat, medium-fat, and high-fat DDGS, respectively. Low feed intakes resulted in negative energy retention and high heat production; therefore, the net energy values of the diets could not be determined. The respiratory quotient (ratio of carbon dioxide production to oxygen consumption) of cattle fed the control steam-flaked corn-based diet was normal indicating carbohydrate oxidation dominated animal metabolism; whereas, the respiratory quotients of cattle fed the DDGS diets suggested that there was also appreciable fat oxidation along with the carbohydrate oxidation. The daily energy losses were similar for the control steam-flaked corn diet and the DDGS diets; so no conclusions can be drawn. The metabolizable energy (ME: as a percentage of gross energy intake) was significantly greater (P = 0.03) for the steam-flaked corn control diet than the DDGS diets and decreased quadratically as fat level decreased in the DDGS diets. These results indicate that reducing the fat content in DDGS also reduces the energy density. The digestibility of fiber in wet DGS is relatively low, thus lowering the energy value of the wet DGS. Experiment 2 is currently in progress to evaluate methods to increase the digestibility of wet DGS fiber. Fifty-four beef steers are individually fed one of three diets containing 30% wet distiller's grains plus solubles. The wet DGS in the diets is either 1) not treated, 2) treated with an enzyme, or 3) treated with a buffered enzyme. Animal performance (weight gain, feed conversion), diet digestibility, and enteric methane production are measured.