Nutritional values of feedstuffs may vary widely due to several factors such as harvest date/maturity, soil type/location, storage and other management practices. Cattle feeding revolves around supplying the necessary nutrients for the current stage of production. Due to inherent variability in feedstuffs, laboratory analysis is necessary to efficiently and effectively feed cattle.
Previously, QLF explained the differences between wet chemistry and NIRS analysis in ‘Understanding Your Feed Analysis Report’ (Deering, 2020). The goal of this article is to help apply some direction on how to use the data derived from the analysis in an effective manner to support long term animal performance goals.
Laboratory Analysis is a Guide
It’s important to utilize laboratory analysis for what it is, a snap shot in time to provide a general guide to nutritional decisions. The data should not be looked at as a definitive measure of a feedstuff but more of a suggestive value. Laboratory analysis is particularly handy to look for swings from normal and to follow trends from crop to crop.
Tracking feedstuff values over time provides a great guide to making inferences to the feedstuff and may help direct planting/harvest behavior in the future. Connecting the feedstuff nutritive trends to animal performance is the ultimate guide to animal production.
Do Not ‘Chase’ Nutrient Values
From time to time, you will likely see a nutrient value on a feedstuff reported that seems too good to be true. If it seems too good to be true, it most likely is. Don’t chase extreme reported values only to chase the value back down to normal with your next lab results. Book values on feedstuffs may not be completely indicative of what you are feeding but, most of time, it will be in the ball park.
Apply some common sense to utilizing lab values. If you have been testing hay out of a particular field for 10 years and the crude protein has ranged from 8-10%, the 13% reported this year is likely an aberration or perhaps only indicative of the sample obtained and not the crop as a whole. Using a value of somewhere around 10.5 and making a plan to retest in a couple of months probably makes the most sense.
Laboratory Nutrient Values with the Most Value
Dry matter testing is generally accurate regardless of testing method and can be followed fairly closely. Understanding the DM of the feeds used and the DM of the overall diet is important to understand intake parameters of the cattle themselves. There are on farm testing methods for DM that are effective in monitoring feeds as well.
Crude protein, wet chemistry or NIRS, is also generally accurate. As previously mentioned, I would caution against chasing aberrant values, but overall, these results can be followed fairly closely.
Use Caution
Energy values depicted on feed analysis reports are not actually analytical values. These values are calculated. The number of nutrient parameters and, therefore, the equation used dictates the overall accuracy. Comparing energy values between labs should be done with caution as well. Book values are generally indicative of the energy value of most feeds. Some variation is normal and some feeds tend to have greater variability (i.e. corn silage) based on the crop itself.
Bunk sample data should also be utilized with caution. These samples have a substantial amount of inherent error built into the results. Bunk samples being comprised of various feeds, particle size/shapes and densities leads to this inherent error. This error affects the entire life cycle of the sample, collection on farm, sample dried at the lab, material ground and subsequently collected for testing. It is not advised to make major decisions off of bunk samples, but again, use only as a general guide. Reliance on individual feed testing and careful batching provides the best accuracy.
Flawed but Necessary
Feed analysis is flawed but absolutely necessary to ensure we are feeding cattle to achieve optimal growth performance. The more data that you gather, including tracking of cattle performance relative to feed nutritive value, the better off you will be as a producer. Be careful making major decision off of individual feed tests without considering potential error and animal indicators such as intake, manure characteristics and historical/current performance.
For additional help or with further questions, contact your QLF District Representative.