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Proper Ingredient Sampling Leads to More Precise Rations

By : Dr. Karl Harborth and Dr. Jason Warner, Great Plains Livestock Consulting, Inc.


Feed is the single greatest production cost in cattle operations. Couple this with weaker cattle markets, and margins are slim on the production side of the beef industry. This only increases the need to test feeds for their nutrient content ensuring the formulation of diets is set to your specific operation needs. By testing your current feed and forage ingredients, not only can we make sure you are not over or under supplementing your livestock, but we can also identify any anti-nutritional factors thatmay be present and ultimately determine how to best utilize the feedstuff; Therefore, maximizing your operation’s performance. Most producers and industry professionals understand this importance, but questions continually arise regarding what, when, and how feeds should be tested. Given the unique and persistent weather challenges encountered by many producers across the country this year, feed testing may play a more important role than ever before. Thus, our objective is to review some of the basic principles regarding feed testing and analysis interpretation.

Many feed tests conducted at commercial laboratories that provide us the basic analyses needed to make informed decisions are relatively inexpensive, costing as little as $18, for the information derived. When you consider the value of both cattle and feed in today’s economy, it is easy to see that a small amount of money invested in feed sampling can be easily paid for in the long run. However, there is also no reason to spend unnecessary money on a feed test if it does not provide you the information needed to answer the question you have regarding your feed. This is where your nutritionist can be of help to determine that samples are correctly analyzed by the specific lab they are submitted to. The important takeaway is to make sure we understand what we are sampling for and what information we hope to gain by doing so.

We know that feedstuffs, particularly forages, are highly variable due to many factors. Soil type, fertilization, moisture, and stage of maturity at harvest all impact forage quality aside from the type of plant itself. Likewise, growing conditions, degree of processing, and specific processing facilities are typical influencers on nutrient content for most grains and by-products. Data accumulated at Rock River Labs, Watertown, WI on 1275 grass sample analyses submitted from the Midwest area from 10/1/2018 – 9/30/2019 had a median crude protein content of 11.18% with a standard deviation of 3.76%. d data during the same time frame and region for dried distillers’ grains had a median crude protein of 32.47% with the standard deviation of 4.71%. As you can see the potential variation could drastically alter an expected vs actual ration formulation. Forages are generally considered to be much more variable than grains and by-products, so we recommend routine testing of hays, crop residues, and silages. Other ensiled feeds such as high moisture corn or milo and corn earlage should always be tested because the moisture, processing, and subsequent fermentation process will make them more variable than dry rolled or flaked grain. Bottom line is unless you test them you will not know what you are feeding.

Collecting an Accurate Sample

The goal in taking samples for testing is to obtain the most representative sample possible for the feed in question because the analysis is only as good as the sample. While it is a simple task, following these guidelines will help you obtain accurate results when testing feed ingredients.

When sampling hay or forages, identify and test lots separately. A lot will consist of hay which has been produced from the same cutting, field, and stage of maturity. A minimum of 10 cores or samples should be collected; however, more is optimal. If testing baled hay or other forages, a core sampler or probe is a must and will aid in reducing sampling error because it takes a cross-section of the bale. Grab samples are not ideal but can work if necessary for ground or loose hay. Be sure to take several sub-samples and mix and combine them well before taking the final sample that will be submitted.

How silage is stored will dictate the best way to sample it. Due to safety concerns, bunkers and piles of silage should be sampled by removing silage from the face with the loader and then taking samples from the loader prior to the silage being added to the TMR mixer. Silage stored in tower silos should be collected when it is coming off the unloader. Bagged silage can be cored in a similar fashion to hay but remember to reseal the holes made in the bag after sampling. Regardless of how silage is stored, we recommend waiting to sample silage until a minimum of 3 weeks following harvest because the fermentation process can alter fiber and subsequent energy estimates. Silage samples should be stored in a cool place before shipping unless shipped to the lab the same day.

Grains and other grain by-products such as dried distillers grains or corn gluten feed can vary from source to source and should be tested regularly, primarily for protein or fat content. Random grab samples that equal 1lb should be enough for an adequate analysis.

TMR samples should only be analyzed if a potential problem exists with the mixing process or if we just want to check the accuracy  of our ration formulation. Handfuls of the TMR should be collected from throughout the entire batch of feed immediately after feed is delivered to the bunk. This sample should then be mixed thoroughly, and a sub-sample of that should be submitted to the lab. Individual analysis of the ingredients will give a better estimate of the ration.

All feed samples should also be fresh and shipped to the lab as soon as possible after collection. Don’t allow samples to collect on the dash of the pickup for days or weeks before submitting as sunlight and heating is not good for sample quality. Sample bags, or bottles for liquids, must be clearly labeled with the necessary appropriate information in case samples are separated from submission forms. Your nutritionist or the lab you are submitting to can provide for you all the necessary supplies for proper sample submission. Samples should also be shipped early enough in the week to avoid any downtime during shipping that could affect the quality and accuracy of the results.

Commonly sampled ingredients can usually be analyzed by Near-infrared Analysis (NIR). It is quicker, cheaper, and generally will supply the basic information needed to formulate rations. Wet chemistry is the gold standard of feed analysis, but it is more expensive and does not have the turnaround time of NIR. There are cases in which wet chemistry is preferred and/or required such as analysis for TMRs or trace minerals. Consult with your nutritionist if you are submitting feed samples to ensure that you are requesting the correct test.

Interpreting the results

Typical lab analysis reports will have moisture, protein, fiber measurements, macro minerals, and energy calculations based off those fiber measurements. Fat, specific minerals such as sulfur, or other trace minerals, may also be of interest. Crude protein is based on the amount of nitrogen multiplied by 6.25. Fat is expressed as a % and determined by an ether extract assay in livestock feed. Energy can be expressed as total digestible nutrients (TDN), digestible energy (DE), metabolizable energy (ME), net energy of lactation (NEL), net energy of maintenance (NEM) or net energy of gain (NEG). It is important to remember that the energy content of a feed is a difficult thing to assess, and the lab-reported energy values are derived from equations, NOT from true chemical analyses like protein and minerals are. There are many established formulas that convert fiber measurements to energy values, but laboratories are not required to use the same standardized formulas. This makes comparisons between laboratories difficult at times and can an also present challenges when interpreting the energy value of high-fiber by-products (distillers grains, gluten feed). Laboratories can further provide information on the source of the formulas they use as well as analysis techniques. Regardless of the lab or technique used, it still provides more accurate information from which to base decisions than the alternative of not testing. If you have any questions or need help getting feed ingredients analyzed, please contact one of our consultants.

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