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Influence of Corn Smut on the Palatability and Digestibility of Corn Silage

 

Influence of Corn Smut on the Palatability and Digestibility of Corn Silage

By Bill Seglar & Bill Mahanna

Common corn smut (Ustilago maydis) is a corn plant fungal disease that infects the stalk and ear of the corn plant. The disease usually is detected after the plant has been insulted such as hail damage and spores from the soil serve as the inoculum to gain entrance into the damaged plant tissue. The result is grayish black galls on the ear of the plant. Smut can have adverse effects on grain yields of corn, however the palatability and nutritional quality of silage made from infected corn aren't well known. Prior research does verify that smut produces little or no mycotoxins. Sheep feeding trials were conducted in Texas to determine the impact of feeding smut infected corn silage on palatability and performance. Sheep are considered a good model to predict how cattle might respond to similar feeding studies.

Results of the in vivo palatability trial and digestion trial indicated that corn smut does not adversely affect the palatability of corn silage. In fact, intakes of smut-infested silage were greater than intake of non-infested silage as shown in the table. Palatability differences could be the result of 1) taste or odor effects, or 2) greater fiber and lesser non-structural carbohydrate contents of silage infested with smut.

Results of in vivo Sheep Feeding Study (corn silage 76% of diet)

Item0% Smut50% Smut100% Smut
DMI 1,047 1,153 1,235
NSC 39.6 30.5 22.7
NDF 40.65 41.36 46.69
WPDMD 75.7 73.6 65.7
dNDF 57.8 57.6 50.8

The non-structural carbohydrate (NSC) concentrations of the 3 diets decreased with increased smut content in corn silages. Very likely smut microbes utilize NSC in corn causing less to be available when feeding silages. Inversely, neutral detergent fiber (NDF) increased with excessive smut content in corn silages because microbes don't utilize fiber for substrate. Therefore as NSC is consumed, NDF will increase. Whole-plant dry matter digestibility (WPDMD) and NDF digestibility (dNDF) decreased with increased smut levels. This is in contrast to a prior 1996 cattle study by Bossuyt who found that increased fungal infestation did not affect WPDMD and tended to increase dNDF. A theory exists that mold activity may affect the integrity of stover cell walls, causing digestibility of NDF to increase under smut infestation, although that outcome was not demonstrated in the Texas sheep feeding trial.

Lower energy values and potential changes in digestibility should be considered when formulating diets containing smut-infested corn silage. Increased dry matter intakes may be realized when feeding smut laden corn silage that is properly balanced into the ration. Based on the findings of the Texas sheep and Bossuyt studies, cattle performance should not be affected from the feeding of smut infested corn silage.

References

  • Theurer, C.B., Huber, J.T., Delgado-Elorduy, A. 1996 Steam Flaking Improves Starch ‘Utilization and Milk Production Parameters.Proc. Cornell Nutrition Conf., p. 121-129.
  • Owens and Prigge, Oklahoma State University.

For reproduction permission, contact:
Bill Seglar
Ph: 515-334-6674
E-mail: Bill.Seglar@Pioneer.com
or
Bill Mahanna
Ph: 515-334-6673
E-mail: Bill.Mahanna@Pioneer.com

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