By Colin Tobin
Late fall and early winter in North Dakota is the time of year where we still have some romance for winter -- before those bitter Westerlies spin counterclockwise to give us lousy low pressure systems. During this time of year, we are maximizing the daylight hours to get as much work done before the early shadows turn to night. Like maximizing daylight hours, feed yards optimize their feed resources to stretch their resources as much as they can. One method of improving nutritive value of grains fed to livestock is through processing.
Cattle are less able than other ruminants to chew (“masticate”) whole grains. Sorghum is the most difficult to fracture, followed by small grains and corn. Whole grains provide minimal surface area for starch fermentation. Microbial digestion proceeds from the inside of the kernel outward. Particle size of the starch determines the rate of digestion, with fine particles digested more rapidly than course particles. Grain processing disrupts the pericarp, or protective covering, of waxy grains like sorghum and corn, allowing more rapid and extensive fermentation and digestion of the starch by the rumen microbial populations.
The intent of processing grain is to maximize total gastrointestinal tract digestibility by maximizing ruminal fermentation while limiting digestive disturbances such as bloat or acidosis. It has been estimated that feeding whole corn decreases average daily gain by 2.5% and increases dry matter intake by 3.2% compared to dry milling processes. Dry milling of grain includes dry rolling and grinding. Steam rolling and flaking adds steam and pressure before rolling. Steam flaking corn is the most common processing method in U.S. feedlots. The steam and pressure process cause gelatinization of the starches, increasing average daily gain by about 6% while decreasing dry matter intake by 5% over dry milling processes.
Along with processing, grain type can affect fermentation rates. Corn and sorghum ferment more slowly than small grains such as barley and wheat. The structure of starches within the two types of endosperms allow for differing rates of enzymatic diffusion. Grain processing can partially or fully overcome these digestion limitations. Barley is typically processed using dry rolling, steam rolling, or temper rolling.
Processing grains improves animal performance but it does not come without risk. Increasing digestion rates of grains, by overloading on grain or other low dietary fiber, can increase the risk of acidosis. Acidosis occurs when the pH of the rumen falls below 5.6 for a period of time. Symptoms of acidosis include reduced feed intake and performance, lameness, and increased temperature. To prevent acidosis, producers should frequently monitor feed intake and animal behavior, provide adequate fiber, and use step-up rations to acclimate animals to increasing levels of concentrates.Source : ndsu.edu