Grain processing increases starch digestibility of feedlot diets

By Jerad Jaborek, Michigan State University Extension

Grains are often fed as the primary source of energy in feedlot cattle diets because of their high starch concentration. Grains, such as corn, have a fibrous protein shell called the pericarp that encapsulates and protects the starch. For the rumen microbes to gain access to the starch inside the kernel, they must first break through the protective pericarp. Grain processing breaks the pericarp, allowing the rumen microbes immediate access to the starch inside the kernel. A greater total starch digestibility results in a greater efficiency of energy or feed use for weight gain and reduced cost for the cattle feeding operation.

Calves and sheep chew and ruminate their feed more than mature cattle, and therefore utilize whole grain-based diets more effectively. When compared with non-ruminants, such as pigs and chickens, who can completely digest the starch in finely ground grain diets, ruminants, such as cattle and sheep, can experience digestive upsets such as acidosis and bloat from overly processed grain. Additionally, grain processing affects the site and extent of starch digestion throughout the various compartments of the digestive tract to a greater degree in ruminants than with the simpler digestive tract design of non-ruminants. Therefore, the desired grain processing for your situation depends on the grain’s characteristics, diet, cattle and feed management.

Corn grain is processed to increase its nutritional value as a feedstuff. The hybrid or variety of grain and its growing conditions can influence the chemical and physical characteristics of the grain. The chemical and physical characteristics of the grain impact its overall nutritional value and affect other factors such as the nutritional composition of the grain, the digestibility of the grain, and interactions with other feed components in the diets such as roughage. Processing specifications, such as grain moisture content, screen size, roll gap, moisture and time when fermenting and steaming time can influence nutritional value as well. Feed bunk management can also influence feed intake, which can have an effect on overall digestibility further adding to the complexity of cattle feeding.

That is why cattle feeding is often called an art as much as it is called a science because of the complex interactions that arise when conditions differ. In this case, Fred Owens reviewed the scientific literature of 46 feeding trials to summarize the effects grain processing has on corn in feedlot diets with less than 20% roughage . Four different types of grain processing were assessed: dry rolled corn, high moisture corn, steam flaked corn and whole corn.

The most common methods of corn processing include grinding or rolling to produce dry ground corn or dry rolled corn, respectively, at about 15% moisture. High moisture corn is created when corn is harvested with greater moisture content and fermented while being stored in a silo bunker. Steam flaked corn is created by adding moisture with steam and crushing the corn kernel between rollers, where the steam gelatinizes the starch making it more fermentable.

The summarized data indicated total starch digestibility throughout the entire digestive tract was greatest for high moisture corn and steam flaked corn (99 and 99%), followed by dry rolled corn (91%) and lastly whole shelled corn (87%). High moisture corn and steam flaked corn resulted in the greatest starch digestibility in the rumen (87 and 84%), compared with dry rolled and whole corn (64 and 68%). Of the starch reaching the small intestine, a greater digestibility was reported for high moisture corn and steam flaked corn (95 and 92%) and only 65% starch disappearance for whole shelled corn and 59% for dry rolled corn.

Very little starch from high moisture and steam flaked corn made its way to the large intestine. Dry rolled corn was digested to a greater extent in the large intestine compared with whole shelled corn. However, starch digestion in the large intestine is less desirable because a large portion of the energy recovered in the large intestine is lost in the feces. If you are concerned about seeing corn kernels in the manure, check out this article, “ Truth or fallacy: cattle cannot digest whole shelled corn? ” The observed improvements in starch digestion with high moisture corn and steam flaked corn compared with dry rolled corn and whole shelled corn are due to reduced particle size and advantageous alterations in the protein matrix that shields the starch from microbial and enzymatic breakdown.

As you may expect, with the improvements in starch digestibility from high moisture corn and steam flaked corn, feed efficiency is more desirable compared with cattle consuming dry rolled corn or whole corn. To determine if corn processing is an option for your cattle feeding operation, make sure the added feedlot performance from grain processing outweighs the cost of grain processing.

Researchers from the University of Nebraska Lincoln reported high moisture corn and steam flaked corn processing were worth the added feedlot performance for 5,000 and 20,000 head feedlots. Costs can vary and have changed over the last 20 to 25 years since this publication. Differences in corn price, feed efficiency response to the diet fed, energy (electricity and natural gas) cost, labor cost, equipment cost and feedlot size will determine if grain processing is economically advantageous for your cattle feeding operation.

If you would like to discuss further or have questions, reach out to the Michigan State University Extension beef team .