Graze Drought Stressed Cornstalks CAREFULLY
Cornstalk residue is a tremendous resource for fall and winter grazing; however, this year care needs to be taken in grazing drought stressed cornstalks due to the potential of high nitrates in the feed.
Cattle prefer grazing the leaves and husk which tend to be lower in nitrates. Because drought stressed corn is smaller and stunted, it is more likely that cattle will eat lower into the stalk where nitrate levels may be high. Nitrates are usually concentrated in the bottom third of the stalk in the corn plant.
High nitrates may not only be an issue in dryland acres but also on irrigated corn edges and in the corners where water hasn't reached and plants are stunted. Cattle tend to prefer these drought stressed plants when grazing. There is the potential that cattle could seek out those plants when first turned onto a pivot-irrigated field.
Due to the shortage of feed this year producers are more likely to leave cows grazing cornstalks longer than they normally would to try to stretch feed resources. Forcing cows to eat more of the stalks increases the risk that they will be consuming parts of the corn plant that could be toxically high in nitrates.
Following are suggestions for grazing potentially high nitrate cornstalks.
- Don't turn cows into drought stressed cornstalks hungry. Make sure the cows are full as this will help them adjust.
- Fence out pivot corners and edges where plants are severely stressed.
- Resist the temptation to leave cattle on corn stalks after they have eaten most of the leaves and husks. Avoid forcing the cattle to consume more of the potentially high nitrate stalks.
- Consider giving cattle a dose of nitrate utilizing microbes 7-10 days prior to turnout. This will help cattle adjust to utilizing potentially high nitrate feed. The use of this product doesn't eliminate the risk of nitrate poisoning when grazing high nitrate feed; it only helps cattle adjust to it.
In the September 14, 2012 Market Journal segment on "Safely Grazing Stalks" (5:28), UNL Extension beef specialist Rick Rasby describes how cows select what to graze in a field. Knowing this can help producers minimize nitrate risk during fall and winter.
Aaron Berger, Extension Educator
Panhandle Research & Extension Center
University of Nebraska
The amount of cornstalk forage available for grazing is likely to be below average this year due to lower yields. The volume of leaves and husks produced are directly correlated with the grain yield. For more information on estimating the amount of grazing in a cornfield based on grain yield see the UNL Corn Stalk Grazing Calculator.
Due to drought conditions this year, many feed resources such as cornstalks have the potential to be high in nitrates. For more information on managing high nitrate feeds please see the UNL NebGuide Nitrates in Livestock Feeding (PDF version, 611KB).
In the "How Nitrates Affect Cattle" (5:47) video below from the NUBeef YouTube channel, UNL Beef Cattle Nutritionist Jim MacDonald explains why a drought causes nitrate problems in cattle.