Vet Column 2-8-10 |

Vet Column 2-8-10

David L. Morris, DVM, Ph.D.
Fort Collins, Colo.

Most feedlot finishing diets contain cereal grain. In order to increase total starch digestibility and energy availability, grains are typically processed. Roughage is fed to maintain rumen health in cattle and to reduce the incidence of digestive disorders including bloat, acidosis, liver abscesses and laminitis (founder). Roughage is traditionally included in finishing diets, but quantities are generally small (less than 10 percent of dietary dry matter).

Including roughage in finishing diets of cattle reduces the net energy for gain, increases the cost per unit of metabolizable energy, and complicates diet handling and management in commercial feedlots. Attempting to minimize or achieve a roughage-free diet must be formulated carefully to avoid digestive disorder and, yet, optimize growth performance. One approach is to provide whole corn in the diet.

Whole corn, because it is not processed, has a slower rate and less extent of ruminal starch digestion when compared with steam-flaked and high-moisture corn. Feeding whole corn should help to avoid digestive disorders by regulating ruminal starch fermentation and reducing accumulation of organic acids in the rumen. Whole corn has been fed successfully to finishing cattle in all-concentrate diets in research trials.

Investigators from the University of Idaho and Washington State University in collaboration with consultants in Salina, Kan., recently reported on a trial involving a direct comparison of diets composed of traditionally processed grain sources, such as dry-rolled, high-moisture and steam-flaked grains. The objective of the project was to evaluate the effects of feeding diets containing whole corn, but no roughage on performance, health and carcass characteristics of steers finished at a commercial feedyard.

Trials were conducted in the Southern Plains of the U.S., using commercial feedyards near Stratford, Texas and Oberlin, Kan. Six feedlot trials were conducted involving 102 pens, 6,895 steers, and a range of 36 to 82 steers per pen. Dietary treatments consisted of a control finishing diet with various grain sources and processing methods that contained a roughage source or a finishing diet, containing whole corn, but without roughage.

In five of the six trials, final body weight was greater for steers fed typical finishing diets than for steers fed whole corn diets without roughage. Feeding finishing diets containing whole corn, but without roughage resulted in decreased average daily gain. Steers fed whole corn finishing diets without roughage in all trials had less dry matter intake. Performance based net energy for gain content of the diet was greater for steers fed whole corn diets without roughage. Differences in USDA yield and quality grades were inconsistent.

Dry matter intake is critical to controlling ruminal acidosis. Subacute ruminal acidosis is associated with reduced feed intake in feedlot cattle. In this study, ruminal acidosis was more prevalent in the non-roughage diet. Although use of whole corn can provide some advantages to management in finishing, such as improving feed efficiency, but only decreasing gain by 3.7 percent as illustrated in this study, use of non-roughage cattle feedlot finishing diets requires increased discipline in monitoring and implementing the total feeding program.

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