A few years ago I was visiting a small cow-calf operation and as I approached the house I noticed that there were rows of snow-covered round bales that literarily looked like baled alligators. The producer told me he baled left-over cornstalks within days of harvesting grain corn, and said that it took a couple of years to incorporate their low nutrient value into his beef cow diets. He had to reject mouldy bales or ones with high nitrates as well as learn the best ways to feed cornstalks. After that, he never worried about having enough forage for his overwintering cow herd.
One memorable thing he told me was not to equate the nutritional value of cornstalk bales with loose-cornstalk residue left in the cornfield for grazing cattle. Baled nutrient value is significantly lower and varies widely, depending upon the percentage of woody cornstalks to husks and leaves. Also, there are virtually no intact cobs with grain corn found inside the cornstalk bales, while several yellow cobs litter an open field of residue.
The accompanying table below compares the nutrient value of average cornstalk bales to corn residue and other overwintering forages.
The nutrient analysis of dry cornstalk bales is shown to be on the lower end of good-quality corn residue, which in the latter is more like barley straw. This signifies that baled cornstalks will not meet the nutrient requirements of gestating beef cows without a respectable amount of energy and protein supplementation, since early- to mid-gestation cows need to consume about 52-55 per cent TDN and eight to nine per cent crude protein diet daily to maintain good body condition, keep warm and support an early-term fetus during the winter.
Used in dairy rations
By comparison, South Dakota State University (2005) researchers supplemented the high dietary energy and protein requirements of growing dairy replacement heifers with a ensiled diet of cornstalks mixed with wet distiller’s mash in a 1/3 forage to 2/3 mash ratio. Over the course of the study, these heifers gained 2.3 lbs. per head per day, which was comparable to heifers fed a traditional diet of alfalfa/grass, corn silage and DDGS.
Although, the dairy diet is not your typical beef cow overwintering ration, it does show how cornstalk bales might be used. Rather than feed an entire diet of 25-30 lbs. of good-quality alfalfa/grass hay (55-58 per cent TDN, 13-14 per cent protein), it would make sense to modify it — with five to 10 pounds of cornstalks, use 15-20 lbs. of the same hay, and with the added option of a couple pounds of screening pellets fed during colder weather. As always, feed a good complementary mineral-vitamin at two to four ounces per head, and provide salt.
The above producer followed a similar feeding program, yet initially tried to feed alternative cornstalk bales in a forage ring without success. That’s because his cows were very selective — they ate available leaves and husks and left mostly cornstalks. He said that he literarily had to starve them to eat more than half a bale. So he changed feeding tactics by grinding each cornstalk bale in a blend with better-quality forage/concentrates to improve overall palatability.
Aside from his practical solution, it is also a good idea to test samples of cornstalk bales for nitrates, because they may accumulate to toxic levels in the lower 20 cm of the plant. Mature cows and replacement heifers can safely consume a diet (dm basis) containing nitrates that are below 0.5 per cent nitrate (NO3). The same bales should also be tested for moulds and mycotoxins, because fumonisin, a common mycotoxin, might infect the entire corn plant. Cattle tolerate up to 100 ppm fumonisin without health and performance issues. Non-specific mould levels will also lower feed intake and digestibility.
Even if these tests come back negative, cornstalk bales will never be the highly nutritious forages that many people use to overwinter their cow herd. However, they can have a fit in beef rations with proper feed testing and proper balance with other feedstuffs.