Testing Feeds: A Recurrent Procedure for Animal Performance and Well-being
Test your feed. You have heard it over and over again. But do you do it enough? To some degree it is the results of the report that can indicate how often, or not, you should sample your feed.
Feeds are sampled and analyzed for different reasons. Commonly, we all want to know the nutrient concentrations, as they can vary considerably. Some may decide to feed high quality feeds to the most productive livestock, whereas the low quality feed is used for animals with lower nutritional requirements. Those who cash crop use the nutritional value to establish a dollar value for selling the crop. However, testing can also be a means to determine the time of harvest, whether extra nutrients should be applied on the field, or approaches to maintain or improve storage and feed-out techniques.
Sampling is the First and Most important step
In a recent Ruminant Feed Industry meeting, Ron Piett of A & L Laboratories stated that sampling is the first and most important step of the entire analysis process. He indicated that the purpose of sampling a product is to determine the quality, through laboratory analysis, to identify the nutritional and anti-nutritional components. Both are just as important. For example, a mineral may need to be added if results are lower than expected, or steps may be taken to reduce the levels if they are too high. The analysis is what eventually is used to "facilitate the creation of a ration designed to maintain good health or optimum performance of the species" says Piett.
Laboratories get their fair share of samples that are difficult to analyze and in some cases impossible. Nelmy Narvaez, of SGS Laboratories commented on common errors that are seen when forage samples arrive at the laboratory. These samples may give an inaccurate representation of the feed from which it was taken, and as a result may not supply the required nutrients for the animal.
Errors seen in samples that arrive at the laboratory for testing are as followed:
- Pulling hay samples from an intact bale causing samples to consist of stems, and no leaves. A large amount of hay samples that arrive at the laboratory are not cored- this is recommended for a representative sample. A core sampler is a long hollow cylinder that is attached to a drill, or used by hand depending on type, to drive into bales to sample from several locations. For round bales, sample towards the middle of the bales. To sample square bales point the rod at a 90 degree angle so that multiple layers are obtained within a sample.
- Samples are unrepresentative. Take samples from multiple spots; mix them to get a homogeneous sample, and then sub-sample approximately 500 gram.
- Too much oxygen left in the sample bag. Remove all air from the sample by pressing the air out before closing it. Oxygen left in the bag will allow aerobic microorganisms to proliferate. The sample bag may generate pressure, causing the sample bag to tear.
- Samples sizes are too big and bags are overfilled. It is difficult to properly mix these, and require more sub sampling in the lab. Overfilled bags can open up during shipping. Therefore, 500g samples are recommended.
- Samples send out to the laboratory on Friday. This often results in samples sitting in a warehouse over the weekend. The fresher the sample, the better!
- Improper labelling. To ensure proper analysis is done, label the samples clearly. Labelling should include what feed it is, date of sampling, and your name or farm name.
How often should I be sampling feeds?
In addition to errors, thought must be given to whether there were any issues at the time of harvest, or storage that would result in inconsistent results. "How often you sample these feeds will depend on the variability within the bunk or silo, and how quickly it is likely to change based on the rate you are feeding it. With greater variability, more samples will be required to understand the composition of what you are feeding", says Chris Roelands of Honeyland Ag Services. "'Common causes of increased variability are the growing and harvesting conditions, multiple cuts and/or different varieties stored in the same bunk, and storage conditions, to name a few. Are there any uncertainties with respect to any of the previously mentioned- if you don't know, find out! And when you do, determine how often you should be sampling and what changes you can make, if any, to avoid this in the future".
William Weiss and Normand St Pierre from the Ohio Agricultural Research and Development Center stated, "We need to start thinking about feed composition data in terms of probabilities rather than actual, absolute concentrations. In other words, how confident are you (or should you be) that the number you have actually represents the true concentration of a nutrient in a feed?"
NIR verses Wet Chemistry analysis
Sample request forms require you to indicate what analysis you would like to have done. Both wet chemistry and Near Infrared Spectroscopy (NIR) are methods commonly used. Wet chemistry measures the nutritional value using heat and chemicals to break down the forage. For example, NDF is the fiber portion that is not broken down when boiled in a neutral pH solution. This is weighed prior to and following the process and difference is calculated. Although accurate, it is time consuming and not as cost-effective as using NIR.
NIR estimates the nutritional value of the feed using light reflection rather than chemistry to identify and measure amounts of compounds in a sample. The reflectance values are entered into calibration equations which estimate nutrient values. The equations are based on studies which compare split samples for wet chemistry with NIR reflectance. This provides fast, reproducible and cost- effective results with minimal sample preparation by the laboratory providing the service, and allows for timely return of analytical results for the customer. However, if your feed was grown under conditions that are significantly different from those in the calibration set, the accuracy of NIR estimates may decrease
Lately, a new term 'aNDFom' has been thrown around in terms of neutral detergent fibre (NDF) evaluations. It varies from NDF in that it is free of ash, which makes it on an 'organic matter basis'. Some laboratories may be giving you aNDFom values, whereas other laboratories still indicate NDF values. An ashing furnace is used to heat samples to extreme temperatures, leaving a residue of ash, which contains the minerals. This is then weighed and subtracted from the NDF portion, giving the 'ash-free' NDF, or aNDFom. Why does this matter? Well, when the NDF is determined, residues of ash are often perceived as part of the NDF value. The variability between NDF and aNDFom varies, as some may have higher ash content due to splashing of soil on leaves due to rainwater, areas prone to flooding, or soil picked up during harvest. This extra step to obtain aNDFom may delay results, but can be valuable to know when evaluating the feed.
Each phase of growth, harvest, storage, or feed-out of a feed involves a quality change, and you have the opportunity to obtain its nutritional value as you see fit. However, to get the most out of your feed, have your feed tested on a regular basis. A simple analysis can go a long way in increasing your bottom line.
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|Author:||Anita Heeg, Feed Ingredients and Byproducts Specialist, OMAFRA|
|Creation Date:||28 January 2016|
|Last Reviewed:||28 January 2016|