Preharvest sprouting in wheat
Preharvest sprouting of wheat is possible in parts of Kansas this year due to the excessively wet conditions at harvest time. Wheat in Kansas usually ripens under warm, dry conditions that favor development of excellent grain for bread making. However, the ripe grain can sprout in the spike when moist conditions delay harvest and promote germination. Severely sprouted kernels usually have slightly to significantly lower test weight than normal kernels, depending on the degree of sprouting.
The extent of preharvest sprouting depends on the duration and severity of moist conditions, the stage of ripening of the grain, and the inherent level of dormancy of the variety. Sprouting begins as the kernels absorb moisture and swell, which activates a number of enzymes that break down starch, proteins, and other constituents for respiration and growth. The seedling roots and leaves then split the seed coat and grow from the embryo (germ), giving the upper canopy of fields a green appearance if moist conditions continue.
Flour milled from the endosperm of sprouted wheat produces bread that is porous and sticky and has a low loaf volume. The grain has little value to the milling and baking industries and is discounted heavily.
More than 4% damaged kernels -- including sprouted kernels -- causes grain to be rated Grade 3 or lower and unacceptable for bread making. Grain that is slightly sprouted might be blended with sound grain for making flour, but grain that is severely sprouted usually is used for livestock feed.
Ripe grain is dormant and must pass through a period of dormancy after ripening before it can germinate, even under favorable conditions. The length of the after-ripening period is highly variable, ranging from a few days in some varieties to a month or longer in others. Differences in the length of the after-ripening period, or dormancy, greatly affect susceptibility of wheat varieties to preharvest sprouting.
Many hard red winter and newer hard white winter varieties are relatively resistant to preharvest sprouting due to their long post-harvest dormancy requirements. However, even with good resistance to sprouting, many winter wheat varieties can still sprout in the spike when conditions are particularly favorable.
Where preharvest sprouting has occurred, producers have three choices:
1. Take the grain to an elevator and accept the price discounts – if the elevator will take it at all.
2. Use the grain for cattle feed.
3. Use the grain as seed this fall.
Sprouted, low-test-weight wheat be satisfactorily used as cattle feed, provided suitable precautions are taken regarding storage and the feeding of wheat to cattle. The following are excerpts from K-State publication MF2659, Feeding Low-Test-Weight and Sprouted Wheat, at: http://www.bookstore.ksre.ksu.edu/pubs/MF2659.pdf
A small amount of energy is lost during germination (of the wheat kernel), which produces heat, carbon dioxide, and moisture. In most cases, germination does not appear to reduce the nutritive value of the grain. In some cases, sprouting may actually improve the feeding value. As sprouting increases to substantial levels, nutritive value of the grain diminishes, but moderate levels appear to have little effect.
Damaged wheat should be stored carefully. Moisture content should be low enough to ensure that mold does not grow within the storage structure. If the wheat must be stored at high moisture content, then it should be dried, aerated, preserved with a storage additive, or ensiled in an anaerobic state (like silage).
Molds may produce toxins that affect feeding value through reduced palatability, intake and performance. Toxins may increase morbidity and abortions in pregnant cattle and, in some cases, may even cause death. If mold is present on kernels, a sample should be sent to a diagnostic laboratory for testing. Young animals, reproductive females and animals under nutritional stress are most vulnerable.
• Damaged wheat and normal corn have similar feeding values, but damaged wheat contains more protein and rapidly fermented starch than corn or grain sorghum.
• Wheat should be coarsely processed to optimize digestibility in ruminants and ground to 700 microns in swine rations.
• Limit wheat to 30 to 50 percent of the complete diet for backgrounding and finishing cattle.
• Adapt ruminant animals to wheat-based diets incrementally, starting with low levels and adjusting the wheat content slowly to desired levels.
• Ionophores should be included in wheat-based finishing diets to improve feed efficiency and reduce the risk of acidosis.
• Buffers like limestone and sodium bicarbonate may be useful to reduce digestive upsets in ruminants.
• Feeding wheat to cattle on moderate- or low-quality forage-based diets should be carefully monitored.
• Inventory should be controlled so that wheat will be included in rations throughout the entire feeding period.
• Feed by weight not by volume.
• The value of damaged wheat is a simple relationship between corn and soybean meal prices (92 plus 8 percent, respectively). This means that 100 pounds of sprouted wheat should be priced the same as 92 pounds of corn and 8 pounds of 48% soybean meal. This value is determined from the quality of the sprouted wheat.
• Proper storage will preserve the feeding value of damaged wheat.
Several years ago, scientists at K-State and the Kansas Crop Improvement Association did a study on the suitability of using sprouted wheat as seed. This research was published in the K-State Agricultural Experiment Station publication Keeping Up With Research 115, Planting Wheat Seed Damaged By Sprouting Before Harvest: http://www.ksre.k-state.edu/historicpublications/Pubs/SRL115.pdf
The authors of the publication concluded:
l. Seedlots that have suffered preharvest sprouting at the level that might occur in Kansas are acceptable for planting if they meet standards for test weight and germination and do not have exposed seedling parts.
2. Sprouted seed may not perform well when planted under adverse conditions.
3. Germination of seed should be measured before planting, especially if it has been stored.
Another publication of interest, although discussing older varieties, is K-State Keeping Up With Research 124, Preharvest Sprouting of Hard Red and Hard White Wheats in Kansas: http://www.ksre.k-state.edu/historicpublications/Pubs/SRL124.pdf
Doug Shoup, Southeast Area Crops and Soils Specialist
Jaymelynn Farney, Southeast Area Beef Systems Specialist
Jim Shroyer, Crop Production Specialist Emeritus