Here are five questions to ask before turning the cows on stalks, including: 
1. What’s left in the field? 

After the corn crop has been harvested, it’s good to know what’s left for grazing. It’s estimated that approximately 50% of the weight of the total corn plant remains in the stalk, leaf, cob and husk components. According to a report from Iowa State University’s Extension Beef Center, “For each bushel of shelled corn produced per acre, 50 pounds of residue is also produced. For example, an acre yielding 120 bushels of shelled corn per acre will produce approximately 6,000 pounds of corn residue.”
2. How long will it last?
With good weather conditions, it’s reasonable to assume that 1 acre of corn residue will provide 60 days of grazing for a 1,000-pound animal, according to the report. In the article from Iowa State University, “Mature cows in the middle trimester of gestation that are in desirable body condition typically maintain their body weight and may gain up to 1 pound per head daily. As the grain component is consumed and availability of husks and leaves declines, protein supplementation may be needed to maintain body condition.”
3. When should I supplement?
Fall calving cows may need protein and energy supplementation, and because corn stalk residue is typically low in a number of minerals as well as vitamin A, a balanced mineral and vitamin mix should be offered free choice. According to the report, “To determine if supplementation is necessary, observe the manure. If little or no corn is visible, protein supplementation should be considered. Sources include alfalfa, corn gluten feed, distillers’ grains.
4. How can I extend the grazing time?
Cattlemen should consider strip grazing to make the corn stalks last longer and offer a more uniform quality of diet. Limiting the amount of stalks the herd can graze at once will force them to be more efficient and consume both the high and low-quality components of the residue. Strip grazing can also limit the damage on the field due to mud or icy conditions.
5. Should I be worried about nitrate toxicity?
According to the report, “Another issue can be nitrate toxicity—especially during drought conditions. The highest level of nitrate concentration in the corn plant is in the lowest part (18-24 inches) of the stalk. This area is typically the last to be grazed by cattle. Therefore, the potential for nitrate issues is unlikely. Soil compaction can also be a concern. Recent research from the Iowa State University Leopold Center for Sustainable Agriculture suggests that compaction is not an issue once the ground is frozen. Prior to freezing, there is potential for slight reduction in yield for no-till soybeans, although there was no difference in soybean yield in conventionally tillage systems.”
 
by Amanda Radke  in BEEF Daily