Don’t Guess at Corn Silage Nutrient Composition
Mar 22, 2013
Follow these three steps for success.
By Dr. Elliot Block, Senior Manager, Technology, Arm & Hammer Animal Nutrition
The easy way to accomplish sound ration formulation with any cropping conditions, but especially when crops are suspected to be variable, is to use the phenomenal modeling programs and lab analytical capabilities that are at your disposal.
Follow these three steps for success:
1. Know which model your ration balancing platform uses.
The major platforms use either CNCPS 5.0 (CPM Dairy), CNCPS 6.1 (AMTS and NDS) or NRC 2001. If you use other platforms, determine which model your platform most closely emulates.
2. Completely analyze forages for the components used in your nutritional model.
Simply knowing the starch value is insufficient, particularly this year. It is just as important to get the correct value for the fermentability of that starch. Corn Silage NDF values alone are not sufficient either. Use the values for rate and extent of NDF digestibility to get the diet closer to correctly predicting animal performance.
• In this regard, NDF is not always NDF and the type of NDF analysis that is best suited for your ration formulation model will differ (see below). Every forage lab conducts the analyses requested and has different forms and formats for requesting the analytical procedures. Make certain to ask for the correct analyses best suited to your ration formulation model.
In addition to the standard nutrient analyses, obtain results for these analyses:
• aNDF: NDF done with the use of Na Sulfite which solubilizes most, but not all, of the protein out of the NDF residue. It is used in the CNCPS 6.1 and NRC 2001 models.
• aNDIP: This is the crude protein measured on the aNDF residue and is used in CNCPS 6.1 and NRC 2001 models.
• NDR: This is the NDF analysis performed without Na Sulfite and is used in the CNCPS 5.0/CPM model.
• NDRIP: This is the protein done on the NDR residue and is used in the CNCPS 5.0/CPM model.
Determine which NDF digestibility assays will be most critical.
• The models currently support the measurement of NDFd at 24 and 30 hours.
• Next year the industry will move to a two-pool model as suggested in the 2009 Cornell Nutrition Conference proceedings. This will mean 30, 96 or 120 and 240 in vitro digestibilities. The 240-hour uNDF will replace the need to do lignin testing and will better recognize the indigestible fiber, which is variable within plant species as well as among plant species. This will allow us to better fine-tune rations for the amount of forage that can be fed—but that is for next year.
Know starch fermentability.
• Ask for a 7-hour starch digestibility. This is a starting point and allows nutritionists to develop Kds (rate of digestion). Researchers are working with the various forage labs to develop a more robust multi point measurement that will increase the robustness of the predicted single-pool Kd.
• It is important that field nutritionists truly understand what to request in an analysis based on ration balancing tools used. For example, if CPM is used, ask for NDR and NDRIP. If 6.1 is used, ask for aNDF and aNDIP.
Lastly, don’t forget, stressed crops may contain more mycotoxins; therefore a mycotoxin analysis is essential as you work with silage.
3. Enter the data obtained from the above into the nutrient profile of the feed.
At this point you can reoptimize the ration and come much closer to accurately knowing how the cow will perform and which ingredients may have to be changed.
By using these available tools, you can avoid weeks or months of subpar performance or nutritionally induced health issues because you decided to use "typical values" for these parameters.
NIR (Near Infra-Red) CAUTION NOTE: Some of the forage analytical labs have robust equations to give reliable estimates of digestibilities by NIR but other labs do not. While NIR will result in accurate estimates for major nutrients (except minerals) in forages, if the forage you work with is not "mainstream," consider requesting wet chemistry for digestibilities and fermentabilities.
Contact Dt. Block at Elliot.firstname.lastname@example.org; or visit Arm & Hammer's dairy website.