Treating Corn Stalks and Other Crop Residues to Improve Feed Value
Shane Gadberry – Associate Professor, Animal Science
The current hay situation and a recent press article generated conversation about treating corn stover with lime to improve feed value. Various treatment regimens have been studied for improving the feed value of low quality forages, including mature grass hays and crop residues such as wheat straw, corn stover, and rice stubble. The following bullet points highlight some of these treatment methods.
Treatment with limestone
- Producers are asking ‘Can we just apply lime to corn stalk bales and improve feed value?’ If the purpose was to improve calcium, yes; however, the real purpose is to improve digestibility. Applying regular feed grade lime to dry forage will not have the same effect on digestibility as the following treatment methods discussed.
Treatment with Calcium hydroxide (hydrated lime), calcium oxide (quick lime), or sodium hydroxide (lye or caustic soda).
- Alkali treatment improves digestibility. Treatment involves adding water to the plant material to bring the moisture content to approximately 50%. The material needs to be chopped to reduce particle size for treatment. Treatment rate is 5% (dry matter basis). Treatment will require mixing for uniform application. Following treatment, the material needs to be stored to exclude oxygen and 7 days between treatment and feeding is required. The chemicals involved are corrosive and should be handled carefully to avoid bodily contact. Become familiar with first-aid, handling, storage, and spill management by reading the material safety data sheet for the chemical. If possible, use calcium hydroxide or calcium oxide instead of sodium hydroxide. Alkali treatment can improve digestibility by 40 to 60%.
Treatment with ammonia
- Anhydrous ammonia treatment will increase protein content and digestibility. Anhydrous ammonia is applied to stacks of dry forage. A pipe is placed within the stack and the stack is completely sealed (top, bottom, and ends) with a heavy plastic. Seams are folded over for sealing and sand, lime, gravel, etc is used around the base to hold the plastic in place. The seam between the pipe and plastic must also be sealed. Anhydrous ammonia is pumped into the pile. The treatment rate is 3% of dry matter content of the pile. After treatment, do not open the pile for at least 21 days and open the stack a day before feeding to allow any free ammonia to escape. Wear protective gloves and goggles when handling equipment and become familiar with first-aid and safe handling by reading the material safety data sheet. Ammoniation can improve digestibility by up to 30% and consumption by up to 20%.
Treatment with urea
- Research has shown modest improvements with urea treatment. As with alkali treatment, urea is applied to 50% moisture residue and ensiled. A 3% (dry matter basis) treatment rate is common in literature. Urea treated material must be stored in a manner to exclude oxygen and stored for at least 21 days before feeding. Adding 10% concentrate feed will increase feed value. Some studies have utilized crushed soybeans which contain a urease to help release ammonia from the urea. Overall, urea treatment does not improve the digestibility to the extent of the other treatment methods, but urea is safer to handle and more accessible than the alternatives. A 15% increase in digestibility can be expected.
In summary, low quality roughages can be chemically treated to improve digestibility, and the ammonia and urea treatment can increase crude protein content. Before treating, study the method you intend to use and develop a good plan for treatment, storage, chemical handling, and first-aid measures.
Since some of these crop residues are very dry at harvest, be aware of the amount of water needed to bring the material up to 50% moisture. For example, corn stalks or grain sorghum fodder may be as dry as 5% moisture or may contain as much as 30% moisture. Corn stalks at 5% moisture would require 217 gallons of water per ton of fodder to bring the total moisture content to 50%. Crop residue at 30% moisture would require 96 gallons of water per ton of fodder to bring the moisture content to 50%.