12 July 2012

3 minute read

North America

Damaged corn can be harvested as either whole-plant silage or green chop, but, either way, growers and livestock producers need to be aware of how it can affect feed quality and animal health.

"Feeding value of drought-stressed corn is influenced by several factors but in general is higher than expected," Keith Johnson said. "Most studies indicate feed value of drought-stressed corn to be 80-100 per cent that of normal silage."

Purdue University studies showed little or no difference in feedlot gain or milk production when beef and dairy cattle were fed normal or stressed corn silage. But, as a rule, Professor Johnson said drought-stressed corn will have slightly more fiber and less energy, but 1-2 per cent more protein than normal silage.

One of the most influential factors is moisture content at harvest.

"Ideally, the crop should contain 60-70 per cent moisture at harvest," Professor Johnson said. "For upright silos, to avoid seepage, growers should harvest at 60-65 per cent, whereas for bunker silos, harvesting at 65-70 per cent moisture will result in better packing and storage qualities."

He said producers often tend to harvest the damaged crop too soon, meaning silage has too much moisture, which can result in poor fermentation and ultimately lower feed value.

Stalks of plants with brown leaves and stalks with small ears or little grain content will be higher in moisture.

"A quick way to determine if the plant contains too much moisture is to hand-squeeze a representative sample collected from the forage chopper," Johnson said. "If water drips from the squeezed sample, the corn is too wet for ideal fermentation."

Livestock producers using drought-damaged corn for silage need to make sure they have the feed tested for nitrate. Nitrate levels can be higher in drought-damaged corn. While the potential for nitrate toxicity after fermentation is recuded, Johnson said it’s still a good idea to have the feed analysed.

Producers with short pasture and stored feed supplies might also consider harvesting drought-damaged corn as green chop.

"There are two major concerns with this practice," Professor Johnson said. "One is the potential for nitrate toxicity and the second is the potential to founder animals."

Animals with founder, or laminitis, have an inflammation of the soft tissue around the hoof bone that can cause permanent damage to the foot.

He offered a series of steps to help avoid these problems:

• Raise the cutter bar to 12 inches the first few days of chopping.
• Gradually introduce animals to green chop.
• Use other feeds that are low in nitrate as part of the ration.
• Feed green chop in small quantities throughout the day, rather than large quantities once per day.
• Don't allow green-chop forage to set on a wagon overnight.
• Feed 2-3 pounds of grain with high nitrate feeds.
• Take extra precautions during the first 2-3 days following rain because nitrate levels tend to increase during this period.

"As plants mature, nitrate levels decline, so animals become acclimated and the chances for toxicity decrease over time," Johnson said.

Corn growers looking to sell drought-damaged corn for silage, and livestock producers looking to purchase it, need to understand how to properly price the crop. Because yield varies widely based on moisture content, Johnson said moisture content will greatly affect pricing.

Purdue Extension offers free publications to help with that process, available here and here.

Before growers make any decisions about what to do with drought-damaged corn, Johnson said it is imperative that they check with crop insurance agents so the crop can be appraised for damage prior to harvest.

He also noted that herbicides and insecticides applied to the corn crop throughout the season have feeding restrictions. Growers need to pay close attention to herbicide and insecticide labels and be in touch with chemical suppliers to make sure the crop is harvested and fed safely.

More information also is available in Professor Johnson's Web-based publication, "Drought-Damaged Corn as Livestock Feed," available for free here.