By Mike Jarosz, Ph.D.
With all the weather challenges this spring 2019 across the country, many crops were planted late, have stunted or delayed growth, potentially later maturity, and/or some producers had to even switch to a crop with a shorter growing season. If these areas receive an early frost, the potential for harvesting immature crops increases significantly. Deciding what to do with immature crops can be a challenge, and their nutrient content and value as feed can be influenced by the maturity level of the crop at harvest.
Corn: With the relatively long growing season of corn, specific fields may not make it to physiological maturity this year, and either silage or high moisture corn might be other options. The following table outlines how the nutrient content of the whole corn plant changes as it matures and which harvest method is appropriate at each stage. In general, immature corn will be wetter, higher in protein, higher in fiber, higher in sugar, lower in starch, and 85-95% the energy value as normal corn silage (Chase, 2013). For ensiling, monitor whole plant dry matter where ideal would be to let the crop stand until reaching a range of 32-34% whole plant dry matter (Chase, 2013), or for high moisture corn reaching a kernel dry matter of at least 60% or greater (Hoffman & Shaver, 2004). The estimated economic value of immature corn silage is 85% the value of normal corn silage adjusted to equal dry matter content (Weiss, 2013).
If the corn does make it to grain, but due to conditions is still immature at harvest, be sure to get the grain analyzed for test weight, moisture, starch, protein and estimate of energy content. Hoffman and Shaver, 2004 suggest corn with test weights from 50-58 lb/bushel have similar energy value and animal performance when fed, but corn with test weights of 50 lb./bushel or less has about 95% the energy value of heavier weight corn.
Forages: With delayed planting, certain fields may have ended up planted to forage crops such as sudangrasses, forage sorghums, etc., the potential concern with these crops would be if they do not grow to maturity and freeze early. The young plants, along with frost damage can lead to toxicity called prussic acid poisoning in cattle, with the greatest potential of toxicity when grazing the forages right after a frost or new growth after a frost. Harvesting as hay or silage is safer (Sulc, 2017).
One concern with harvesting immature and likely higher moisture crops is the greater potential for mold and/or yeast growth, which can lead to spoiled feed, toxins in the feed, etc. Analysis for mold and yeast can be performed on feedstuffs of concern. Depending on fertilization practices, but another potential concern with any stress such as cool, moist conditions and frost on an immature plant can be nitrate toxicity. Ensiling can help decrease the nitrate risk, and feedstuffs can be analyzed for nitrate levels to rule out any risk.
Even crops such as immature soybeans can be harvested as a forage crop if they do not have time to mature. If soybeans reach the late R5 stage (beginning seed development) to the R6 stage (full seed development) or Full Green Bean stage before a freeze, their greater value is as a dry bean crop. In the early to mid R5 stage, their value is likely greater as a forage with the nutrient content being similar to other legumes such as alfalfa hay (Barnhart & Pedersen, 2008).
Depending on how the rest of the growing season plays out, there is potential for immature crops being harvested this fall. The crops still have good value, especially if harvested and stored appropriately. To best use the crops as feedstuffs, obtain an analysis of each of the feeds and work with your QLF representative to determine the best means to feed them within balanced rations.
2017 Immature Corn Silage Crop Poses Harvest, Feeding Challenges.Dairy Herd Management.
Hoffman, P. and R. Shaver. 2004. Dairy Cattle Feeding Tips For Immature Corn. Dairy.
Chase, L. 2013. Considerations For Working With Immature Corn Silage. Cornell University Cooperative Extension.
Lauer, J. 2004. Negotiating the Value of Immature Corn Silage. Wisconsin Crop Manger. 24:158-161.
Barnhart, S. and P. Pedersen. 2008. Harvest Late Maturing Soybeans for Grain or Forage. FarmProgress.
Sulc, M. 2017. Dangers of Harvesting and Grazing Certain Forages Following a Frost. The Ohio State University-Agronomic Crops Network.