Although the Southeast has suffered through some horrendous flooding in the last few weeks, most of the rest of the country has experienced a warm, dry period this late summer/early fall. Throughout the Midwest, the last 6 to 8 weeks have been characterized by an abundance of sunny and windy days which is conducive to the rapid drying of this year’s crop. As a result, the average corn silage samples coming into our lab since mid-September have averaged around 63.5% moisture. Starch levels are just over 35% which is good, but 7-hour starch digestibility is only 81% which is quite a bit lower than we would like to see. Fiber digestibility is also less than ideal since abundant moisture during early summer enabled rapid stalk growth and additional lignin production.
Hopefully, most producers are still feeding their 2014 corn silage, but what about those who have to start feeding this year’s crop right away? What challenges will they be facing in the next few weeks?
First, drier silage is harder to pack, leaving air pockets and a “spongy” feeling when you walk over the bunker or pile, so density and therefore storage capacity, is lower than normal. A good, lactic-acid producing fermentation can’t take place until all of the oxygen is used up in the silage mass, and this aerobic respiration causes heating. That, coupled with the warm ambient temperature during ensiling means that the silage will come out warmer than usual, even if no spoilage organisms are present. Also, additional carbohydrates are used up during this excessive respiration, so the 6-C sugars will be lower than normal which leads to lower energy in the silage. Please remember that drier silage needs to be treated with higher rates of Silo-King since there is more dry matter per ton that needs to be treated. The antioxidant in Silo-King can help eliminate excess trapped oxygen so fermentation can get started sooner, and the efficient, lactic-acid producing E. faecium bacteria work to lower the pH quicker. The fibrolytic enzymes in Silo-King will help break down fiber into simple sugars which are then available for conversion to fermentation acids to speed up the natural fermentation process.
Next, because of the lower silage moisture level, the bacteria will take longer to produce the amount of acid necessary to preserve the silage, so try to avoid opening the silo for as long as possible. This long period of aerobic conditions followed by slower acid production permits spoilage organisms like yeasts and molds to multiply rapidly so watch for silage that comes out excessively hot, or that will re-heat when it is exposed to air. The ingredients in Silo-King work together to help minimize heating from mold and yeast growth.
Finally, because of the more mature crop, kernels will be drier and harder so the silage, especially if it is poorly- or non-processed, will have much lower starch digestibility this fall until the silage acids have a chance to soak into the kernels and start to soften up the starch and hydrolyze some of the prolamin proteins in the kernel. Starch digestibility will improve with time in storage, however, drier silage will not ferment to the extent that higher moisture silages do. Consequently, overall starch digestion in the drier 2015 corn silage crop may be lower this year. Time will tell.
How can we adjust the diet to help maintain production in the face of these quality issues?