High Inclusion Corn Silage Feeding Guidelines
By Bill Seglar, DVM, DuPont Pioneer Senior Nutritionist
Success in feeding corn silage involves following a hierarchy of observations and measurements in the nutritional program. The corn silage evaluation plan becomes essential when evaluating beef rations containing higher corn silage inclusions.
Evaluating Corn Silage
Start at the silo. This will help determine your ration formulation considerations. With safety in mind, you should physically determine face management on horizontal silos and what the silage looks like coming out of vertical silos. Determine with calculations if at least 6” is removed daily from the entire face in winter months and at least 8” during summer months.
Look for signs of spoilage and, if extensive, try to assess how spoiled feed is handled. Determine if corn silage is being fed from more than 1 silo and how many different hybrids exist in the silo. This is helpful during the feedout season in determining how often and when to sample forages for monitoring dry matter, starch and neutral detergent fiber (NDF). Look for any signs of heating in the silage.
Look at kernel damage and chop length. Kernel damage often is an overlooked aspect of assessing corn silage quality. Beef research shows variable results on value of kernel damage in beef rations. However, kernel processing becomes more important for beef producers who background cattle or for those producers finishing out cattle with high-corn silage rations. Scoop as much silage as possible in both of your hands from several locations across the face of the bunker. Then spread the silage onto the bunker floor and pick out any kernel pieces that are larger than a quarter kernel.
If the sample contains more than 2 or 3 of these kernel pieces, you should then conduct a kernel processing score that can be performed at major forage testing laboratories to help in potentially discounting the energy value of the silage. This is also a good time to determine chop lengths of the silage.
Monitor feed delivery. Monitoring for particle size is very important in a high-corn silage ration. In addition to you looking at corn silage chop length (ideally about ½”-¾”), observe also the chop length and texture of the other forages that are going into the feed mixer wagon for determining functional fiber levels in beef rations.
Review the mixer wagon during the filling process to observe both feed sequencing and length of time the corn silage has been exposed to mixing. A common problem with extended mixing times is excessive breakdown of forage particles needed for rumen stimulation and cud chewing. Shorter mixing times result in forages not being adequately mixed with other concentrate feed components in the ration. Particle size determinations and nutritional analysis of the ration at feed delivery are often helpful to detect feed mixer wagon abuse of fiber particle size as well as to assess feed mixer consistency.
Observe cattle eating patterns. Beef cattle are the ultimate judge and, therefore, should be observed for feeding behavior, cud chewing, manure consistency and appearance of the ration in the feed bunk. Other observations, such as interest by cattle in approaching the feed bunk when fresh feed is delivered, locomotion patterns and incidence of cattle chewing their cuds when lying down, also should be assessed. This will help determine if any degree of acidosis is resulting from the feed mix where then ration changes can be made to mitigate changes of acidotic and, eventually, lame cattle.
Additional fiber needs may be needed in some herds feeding high-corn silage rations by resorting to incorporation of dry hay in the ration to help stimulate rumination and cud chewing. Use of such forage sources should be tub-ground prior to placing in the mixer wagon to ensure particle lengths are short enough so cattle are less apt to sort out the less palatable dry hay.
Fiber. Nutritionists understand they must balance for the amount of nutrients and not just percentages. The NDF content contribution from corn silage needs to be considered in balancing of the ration. Higher starch concentrations in corn silage dilute the NDF content. This is why monitoring absolute pounds of forage NDF intake and paying close attention to the condition of the manure is what continues to guide the ration adjustments of many field nutritionists.
Starch. Laboratory starch values have become commonly available and nutritionists now have a better grasp on supplemental grain needs to complement the starch delivered by modern hybrid genetics from corn silage in the ration. The effect of longer silo storage times for corn silage and high-moisture corn will increase ruminal starch digestibility.
The level of starch that can be safely fed in beef rations also depends on degree of processing in addition to length of time in silo storage. It is virtually impossible to exceed high-end starch feeding levels in rations with corn silage, even under the highest inclusion rates of the high-starch corn silage. Increased starch digestion with longer storage times in the silo makes it common for nutritionists to adjust starch feeding levels in the feed mix from time the silo is opened in the fall compared to spring and summer months. A good way to determine if cattle are maximizing starch in the ration is to monitor fecal samples for presence of excessive whole corn and corn particles. Fecal starch analysis is another monitoring tool that is a more recent laboratory offering by some feed testing laboratories.
Fat. Corn silage contains about 3.5-4.0% fat, while high-oil hybrids contain 6.0-8.0% fat. These fats are highly available to the rumen. High-corn silage inclusion rations require close attention because while they provide the opportunity for enhanced dietary energy density, too much rumen available fat can result in rumen health issues.
Protein. A better nutritional understanding of beef protein supplementation has helped with managing rations with high-corn silage inclusion rates. Crude protein (CP) containing higher rumen degradable intake protein (DIP) sources and urea supplementation complements high-corn silage rations by promoting high microbial protein yields. However, having excess CP and DIP is a luxury that can no longer be tolerated as soybean meal prices elevate and there exists increased concerns of nitrogen-related nutrient management environmental concerns. Excessive CP also takes up space in the ration that could be filled with an energy source.
Higher-energy beef rations require increased urea-nitrogen to maximize rumen efficiencies in the production of microbial protein. Beef nutritionists use ration software that tracks protein utilization in the rumen and small intestines that allows for more protein feeding efficiencies.
Corn silage inclusion rates are on the rise due to availability of supply, energy density, consistency and palatability. Close attention should be paid to silage starch content, NDF content and digestibility and physical attributes such as effective fiber, kernel damage and feed storage/delivery management.
This article was originally published in the Sept. 24, 2015, issue of Progressive Cattleman, and is reproduced with permission.