Feed Testing & Analysis for Beef Cattle

When you don't know the quality of feed on an operation, maintaining animal health and welfare can become significantly more difficult. Visual assessment of feedstuffs is not accurate enough to access quality and may lead to cows being underfed and losing body condition, or wasting money on expensive supplements that aren't necessary.

Why feed test?

1. Avoid sneaky production problems, such as poor gains or reduced conception caused by mineral or nutrient deficiencies or excesses;
2. Prevent or identify potentially devastating problems due to toxicity from mycotoxins, nitrates, sulfates, or other minerals or nutrients;
3. Develop appropriate rations that meet the nutritional needs of their beef cattle;
4. Identify nutritional gaps that may require supplementation;
5. Economize feeding, and possibly make use of opportunities to include diverse ingredients;
6. Accurately price feed for buying or selling.

Obtaining Feed Samples

Obtain 20 cores for each sample you wish to submit using a forage probe.
Photos courtesy of SK Ministry of Agriculture.

It's critical to collect a feed sample that is representative of the feed ingredients that you are testing. Any feed type that will be used to feed beef cattle can and should be analysed, including baled forages and straw, by-products, silage, baleage, grain, swath grazing, cover crops, and corn.

Feed quality will change as the feeding season progresses. Samples should be taken as close to feeding or selling as possible, while leaving enough time for the results to come back from the lab.

For baled products, use a forage probe to obtain a minimum of twenty cores for each sample you wish to submit. Sample square and round bales 12-15” deep and stacks or chopped hay 18” deep. Round bales should be sampled from the side (round end) and squares should be sampled at the end. Separate your forage inventory into lots with similar characteristics – same field, same maturity at cutting, same plant composition, etc. Hand grab samples will not be representative enough to give accurate results.

Some counties, rural municipalities, applied research associations, and forage testing labs also have probes for rent. Forage probes can be purchased from farm supply stores and range in price from about $100 to upwards of $500 for fancier drill driven models. Producers can construct their own forage probes but should ensure the diameter is between 3/8” to 3/4”. The tip should not be angled, and needs to be kept sharp regardless of whether it is serrated or not. The probe should not be longer than 24 inches.

Collect the forage in a plastic zip-lock bag, removing as much air as possible before sealing. Clearly label with your name, the type of forage, the lot/area where the sample was collected, the date of sampling and any notes that might affect the results. For silage, collect hand samples or use a longer probe, from the upper, middle, and lower parts from four quadrants of the silage pile or pit as long as it is safe to do so.

This will result in a larger sample size than what can be submitted. Mix these samples well and obtain a sub-sample from the combined material. For swath grazing or standing crops, obtain representative samples of the sward (for swaths) or the whole plant, according to lab specifications.

Click to view Feed Samples PDF

What Should I Test For?

This can depend on the types of feeds being tested, the management decisions you need to make, and how much you are willing to spend. Generally, hay and greenfeed analyses should include dry matter, crude protein, acid and neutral detergent fibre, calcium, phosphorus, potassium and magnesium. Silage tests should also include pH; if the pH is less than 5, it has been properly fermented.

Forage that is baled or ensiled when it is too wet can undergo heating and become brown to black in colour with a sweet, tobacco-like smell. This means that some of the protein in the forage will become unavailable to the animal. If heat damage is suspected, analysis of acid detergent insoluble nitrogen or protein (ADIN or ADIP) should be requested. Heating can also produce nitrites, which are ten times more toxic than nitrates.

Some by-product feeds (such as distillers' grains) or annual forages (such as canola or mustard) may have high levels of sulphates. This can cause polio in cattle. Other considerations include nitrates and mycotoxins.

Near Infrared Reflectance Spectroscopy (NIRS)

It is important to understand the benefits and limitations of testing methods. NIRS uses different wavelengths of light to interpret the kind and amount of organic nutrients present in a sample. The calibration values for NIRS are based on wet chemistry (the gold standard for forage analysis), but it is important to make sure that the lab is using NIRS equations that are appropriate for the samples being tested. For example, a different calibration equation should be used for canola straw versus mixed-grass hay and for fresh or dried sample types. Mineral calibrations are based on an indirect relationship between minerals and organic molecules in the sample, ignoring any inorganic sources, which can lead to higher error rates when NIRS is used for mineral analyses. NIRS is generally faster and cheaper than wet chemistry, but wet chemistry may give a more accurate result for some analyses (particularly minerals).

How to Interpret Results

Feed quality differs according to forage species, stage of maturity at time of harvesting, weathering of forages, storage conditions, plant disease, and other factors. It is important to not rely on averages and to test feeds annually. Forage quality can vary significantly within a field and year to year.

Meeting Nutrient Requirements for Cattle

The main reason producers should test their feed is to ensure they are meeting the nutritional needs of their livestock. Nutritional needs vary greatly depending on stage and age of cattle and whether you are growing, finishing, breeding, or maintaining cattle. Body condition score, hide thickness, and hair coat can affect nutrient requirements of cattle, as can weather conditions like precipitation, temperature and wind speed, or environmental factors such as mud depth, bunk space, or other factors. An example of nutrient requirements for cows compared to bred heifers is in the following table. A common rule of thumb is 55-60-65 and 7-9-11 for the percentages of TDN and CP, respectively, required by a beef cow in early-, mid-, and late-gestation.

* Values are from www.BeefResearch.ca and were generated using Alberta Agriculture's CowBytes Program, with assumptions including breeding for June 1 calving, typical Canadian winters, access to shelter from wind and a daily gain of 1.25 pounds for bred heifers in addition to weight gain from pregnancy.

Interpreting Lab Results

Most labs provide basic information on moisture content, protein, energy, total digestible nutrients, fibre, and some vitamins and minerals. More specialized tests may include results for pH, ADIN, nitrates, toxins, relative feed value (RFV), and other parameters.

Dry Matter (DM, %) refers to the moisture-free content of the forage sample. The water content of forage will dilute nutrients, yet doesn’t usually have a great impact on animal intake, therefore it’s important to balance all rations on a dry matter basis. The daily intake of beef cattle will be ~2%-2.5% of body weight on a dry matter basis. Moisture contents outside of expected ranges can indicate potential spoilage issues. Wet grains (40% DM) silages may not ensile well leading to heating, clostridia or listeria contamination or excessive aerobic losses and spoilage.

Organic Matter/Ash (%) is derived by determined the DM component. Measuring the ash content allows the sample to be split into organic matter and inorganic (mineral) components. Excessive ash content (>6-8%) can indicate soil contamination in the sample.

Crude Protein (CP, %) is an estimate of protein based on multiplying nitrogen content of the sample by 6.25 (the nitrogen content of protein is ~16%, 100 ÷ 16 = 6.25). Protein digestibility can vary and proteins may be bound in indigestible forms (e.g. heat damaged proteins). Non-protein nitrogen (NPN) sources like ammonia or urea increase crude protein values but depend on microbial activity and dietary starch to have any nutritional value.

Neutral Detergent Fibre (NDF, %) indicates the amount of fibre content in the plant. High levels of NDF (above 70%) will restrict animal intake. More mature forages will have higher NDF levels.

Acid Detergent Fibre (ADF, %) measures the least digestible portions of the forage plants, such as cellulose and lignin. High ADF indicates poor digestibility of the feed. High quality legumes generally have ADF values between 20-35%, while grasses can range from 30-45%.

Acid Detergent Insoluble Nitrogen (ADIN, % of total protein) also referred to as acid detergent insoluble protein, acid detergent insoluble crude protein, acid detergent fibre protein, insoluble protein or bound protein) is a measure of heat damage that can bind protein and make it unavailable to the animal.

Total Digestible Nutrients (TDN, %) is defined as digestible carbohydrate + digestible protein + (digestible fat x 2.25), reflecting the greater caloric density of fat. A TDN value can be converted into estimates of digestible, metabolizable, or net energy. It's most useful and accurate for rations comprised primarily of plant-based forages.

Relative Feed Value (RFV) is an index that estimates intake and digestibility and is useful for evaluating 100% alfalfa hay or silage only, with full bloom alfalfa hay used as the baseline with a RFV of 100. Values below 80 normally will not meet animal requirements for energy. It is not reliable for mixed hay, grass hay or cereal greenfeed. It is often used for price discovery but is not helpful when balancing rations.

Relative Forage Quality (RFQ) is an index that estimates intake and TDN. The estimate of intake is based on different equations for grasses versus legumes or legume-grass blends and includes additional factors to improve the accuracy of prediction, as well as in vitro measures of NDF digestibility. RFQ can be used for legume, grass, and legume/grass mixtures. The RFQ value for full bloom alfalfa hay will be similar to the RFV, but when samples differ in NDF digestibility, RFQ will differ from RFV.

Many feed analysis reports will include calculations of digestible energy, metabolizable energy, net energy for gain, net energy for lactation, and net energy for maintenance. Differences in the way these are calculated may exist between labs. You can input your forage results into the calculator at the top of the page to see if it is suitable to feed to cattle as is or if you will need to blend with other feed.

Preventing Problems

One of the major benefits of feed testing is preventing costly and devastating problems before they start. Every season is different and some years there is an abundance of high quality forage. Other years, there is a lack of available feed, or perhaps there is an abundance of low quality forage, grain, or grain by-products available that may look economical but can potentially pose significant risks if a feed analysis has not been performed or understood.

Moulds & Toxins

Mould can occur in forages, grains, clover, corn, and by-products or derivatives of those feed ingredients. Moulds occur due to plant diseases such as ergot, fusarium head blight, Aspergillus, and many others. The incidence of these plant diseases increases during cool and wet growing conditions, or in crops left standing throughout the winter. Mould will reduce the energy content and palatability of feed. Mouldy feed can also cause production problems including abortions and respiratory disease and can cause the development of mycotoxins in feed. Mycotoxins such as alkaloids, vomitoxin, and aflatoxin can lead to reproductive failure, reduced milk production, depressed gains, convulsions, gangrenous symptoms (i.e. sloughing of hooves, ears or tail), and death.

Avoiding moulds in feed isn't always possible, so it’s important to test feed to determine how much and what type of mould may be present so producers can realistically deal with the situation. Avoid feeding mouldy feed to young or pregnant animals, and obtain guidance from a nutritionist about safe ways to blend potentially problematic feed to dilute the contaminants. Prairie Diagnostic Services Inc. has a helpful mycotoxin calculator available online to assist producers with determining their risk level.

Access the calculator online HERE.

Mineral Nutrition

Mineral nutrition as provided by forages depends on:

• Feeding situation (i.e. grazing pastures vs. winter-feeding);
• Plant species;
• Forage management;
• Stage of plant growth;
• Soil type and zone;
• Weather;
• Available stock water and water quality.

Trace minerals, particularly copper, zinc, and manganese, are important for the reproduction, health, and growth of an animal, and almost always require supplementation. Other minerals, such as molybdenum and sulfur, have antagonistic properties that work against an animals’ ability to absorb these minerals. Stock water that contains high levels of sulphates, or forages that contain high levels of sulfur, such as Brassicas (i.e. canola, radish, turnip), can interfere with copper absorption and cause deficiencies. Soils and/or forages high in molybdenum can also lead to copper deficiencies, so producers must consider all sources of minerals when consulting on their supplementation needs.

In most cases, minerals must be supplemented year-round. Producers should work with a nutritionist to ensure they understand how their mineral supplementation program works, and that they are meeting the needs of their cattle depending on the stage of breeding or gestation. It's also critical to determine whether the products they are purchasing are being consumed (and minerals are being absorbed) at appropriate levels, by all cattle.

Nitrates

Annual crops such as oats, barley, corn, or millet can accumulate nitrates under certain growing conditions, including severe drought, hail storms, or frost. Cattle can metabolize a certain level of nitrates, but if the diet contains more than approximately 0.5% nitrate (NO₃) on a DM basis subclinical toxicity can occur causing reductions in weight gain, decreased feed intake and milk production, and an increased risk of infections. Diets containing more than 1% NO₃ may result in death loss and abortion. Mature cows and replacement heifers are most at risk and can have symptoms such as abortions, premature calves, newborn calf mortality, poor growth and reduced milk production.

A simple and cost-effective feed test can rule out potential problems due to nitrates. Depending on the level of toxicity, the feed may be blended off to dilute the nitrates to safe levels.

What About Water?

Feed testing is critical, but beef cattle also obtain nutrients from water. Producers must consider regularly sampling stock water to prevent nutritional problems. In many cases, forage alone or water alone may not cause toxicities in beef cattle, however when the two are combined, the cumulative effects may lead to problems. This may be particularly true for sulphates or nitrates and can occur in either grazing or winter feeding situations.

Testing stock water quality may be particularly important during a drought, when minerals and nutrients may become concentrated as water tables drop in surface or ground water, or evaporation occurs in stock ponds.

For more information on water testing, quality and systems go to: http://www.beefresearch.ca/research-topic.cfm/water-systems-for-beef-cattle-104

Formulating Rations

Producers may wish to use software such as CowBytes, a low-cost program available to producers to help formulate rations.

Once feed test results are available, producers can formulate an appropriate ration for their cattle using the services of a qualified nutritionist, the assistance of agriculture extension staff, or through a software program such as CowBytes (Version 5). CowBytes is currently available for purchase through Alberta Agriculture and Forestry. There are also several free, useful online tutorials available.

Different rations need to be developed for as many separate classes of cattle as necessary. Producers may choose to group their herd according to needs. For example, a breeding herd may be split into one group of mature cows that have a good body condition score and simply require maintenance, and another group of older or thin cows that need to gain weight.

Minerals and salt most often need to be supplemented during the winter feeding period according to feed results. For rations comprised mainly of alfalfa, grass, or a mix of the two, calcium and phosphorus typically needs to be supplemented in a 1:1 mix. For rations that contain more cereal-based forages, including pellets, straw, or greenfeed, supplementation of a 2:1 or 3:1 mix may be required. Animal needs will also change as they move through gestation and lactation.

Interested in feed testing? What's next?

• Assess your feed resources. What types of feeds are you planning to use and which tests best suit your forage types?
• Do you have the right tools, including a forage probe? Are the samples you've collected representative of your feed types?
• Evaluate your goals for feed testing. What is motivating you? How do you plan to use the results? Have you contacted a nutritionist, agrologist, or veterinarian that you can work with to interpret the analyses?
• Are there potential problems you want to avoid? For example, are you concerned about the risk of mycotoxins in barley, or nitrates in a crop that was stressed? Have you or your neighbors had particular problems in the past?
• Understand the realities of potential results and study your feeding options. If your feed is poor quality or contains potentially dangerous toxins, how can you use it best? Do you have experience using poor quality feed? Do you understand the risks of using potential problem feeds?