Steve Paisley: Maximizing the grazing potential of corn stalk residue
Corn stalk residue is an economical forage resource that becomes increasingly important as fall hay prices in the west continue to rise. However, in order to adequately utilize corn residue, there are a few items to consider.
• Quality of corn stalks. Corn residue is unique in that all of the feed is available at the beginning of grazing (no subsequent growth to rely on), and forage quality is highest when cattle are turned in. The quality of individual plant parts such as husk, leaf, stem and cob (Table 1) change very little during the grazing period. However, as cattle continuously graze a field, they will select the highly digestible husks and leaves, resulting in a decline in quality of the remaining field residue.
For spring calving herds, initial quality of the available forage will adequately maintain weight and desired body condition. But because the husks and leaves represent only approximately 39 percent of the available forage, nutrient intake can quickly drop below the threshold level to maintain weight and to also adequately digest the remaining forage.
It is important to recognize the disappearance of husks and leaves from the fields, and to provide supplemental feed to improve the utilization of the remaining field residue, and to maintain weight and body condition of the cowherd.
• Stocking rates. Several factors should be considered when estimating the correct stocking rate, such as grain yield of the field (used to estimate the total amount of grazing residue available), desired performance of the cattle, and the length of the grazing period. With high producing corn, there will be about 16 pounds of leaf and husk per acre. The specific relationship is: pounds of leaf and husk per acre = ([bushels/acre corn yield X 38.2] + 429) X 0.39. (2004 Nebraska. Beef Report).
If you estimate 50 percent utilization of the leaf and husk, 1 acre of 150 bushel corn residue would carry a 1,200-pound cow for approximately 44 days, or a 600-pound calf for 88 days.
• Supplementation. While initial forage quality of corn stalks is adequate for mature, pregnant cows, additional protein will improve forage utilization, forage digestibility and overall performance. This becomes increasingly important after cattle have selectively grazed the highly digestible leaves and husks. In addition, weaned and backgrounded calves will require additional protein and energy to maintain acceptable gains, especially when weather becomes a factor.
Three to five pounds of alfalfa has traditionally been an excellent compliment to corn stalk residue, with the amount of alfalfa increasing as cattle continue to graze stalks. However, as hay prices continue to climb, additional byproduct feeds such as corn gluten feed and dried distillers grains are excellent sources of supplemental energy and protein. Distillers dried grains are high in protein (28-32 percent crude protein), high in energy (100-125 percent the value of corn), and phosphorous (0.5-0.6 percent). Additionally, DDG is a safer “high fiber” energy source that compliments low-quality forages very well. The amount of supplement fed will depend on the amount and quality of remaining forage, as well as the desired cattle performance and cattle type, but a general recommendation would be to provide 0.5-0.9 pounds of supplemental protein (1.7-3.0 pounds distillers dried grains/day).
• Maintaining cow body condition. As producers continue to try to minimize production costs while maintaining an acceptable level of performance, and as hay prices continue to rise this fall, the tendency is to “over” graze these alternative forage resources. It is critical to watch cattle closely and maintain adequate condition as preparation for winter months.
Although reducing feed costs is an important way to reduce overall operating expenses on the operation, it may ultimately be counter-productive. Current research continues to stress the importance of nutrition during pregnancy, and it’s ultimate impact on the subsequent calf crop. In addition, cattle need adequate fat cover to maintain body temperature during colder weather. Several studies indicate that thin cows require about 6 percent additional feed just to maintain weight during the winter months. This amounts to a minimum of an additional 1-1.5 pounds of feed/day, just to bring the thinner cows up to “par” with cows in average condition.
• Summary. Corn crop residue is an important forage resource where available. Dry, pregnant cows are perfectly suited to utilize this unique feed resource. While forage quality and quantity are essentially “set,” continued grazing and selection of the higher quality leaves and husks mean that overall forage quality and quantity declines as grazing continues. Supplementation strategies utilizing higher protein supplements will help to maintain diet digestibility and cow performance.
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