UKVDL 2012 Forage Nitrate Testing Guidelines

The University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) performs forage nitrate/nitrite testing and accepts samples from veterinarians, extension agents, and producers. Nitrate accumulation in forages is a real concern this season due to current drought conditions.

A panel including both nitrate and nitrite analyses costs $15 per sample, and turnaround time is one to three business days.

Sample Collection Guidelines

Proper sample collection is crucial for correct interpretation of results. The sample should represent what animals will be eating, so collect the entire part of the plant that will be fed. Collect a number of smaller samples to form a large representative composite sample. If different regions of a field were treated differently, then submit separate composite samples for each different region. Sample different cuttings, batches, or fields separately, and submit them as separate samples.

Submit at least a pound of total composite sample. More sample is better than too little, so when in doubt collect more. Be sure to mark each bag legibly with forage/sample type and identification information.

Nitrate concentrations tend to be higher in the stalks and at the base of the plants than in the leaves. Grains, seeds, and leaves do not accumulate significant nitrate levels. Plants with high stem-to-leaf ratios are the most likely to cause nitrate intoxication.

Dry forage (hay or bedding)--Use a hay probe to take core samples. Randomly select 10 or more bales that are representative of a cutting/batch. Take one or more core samples per bale, and mix all the cores to make one large composite sample.

Silage, balage, haylage--Use a hay probe to take core samples if possible. Randomly select 10 or more bales that are representative of a cutting/batch. Take one or more core samples per bale, and mix all the cores to make one large composite sample. Reseal the hole created in the wrap with tape after sampling. For bagged silage, select at least 10 representative areas to sample. If core sampling is not possible, unload some silage material and collect large handfuls from 10 or more different locations. Mix to form a large composite sample.

Corn stalks--Cut the stalks at the anticipated harvest level and submit the entire part of the stalk that will be fed. Collect stalks from several areas of the field. Five to 10 stalks are recommended. Stalks can be cut or folded prior to shipping. Alternatively, if the corn stalks are going to be chopped, you can collect representative samples from the fresh chop. Or, if shipping volume is an issue, only submit the bottom halves of the stalks, but remember the result will be higher than the actual overall average nitrate concentration for the entire plant.

Pasture grasses--Collect handfuls of forage from 10-20 different areas in the field. Cut the grass at the anticipated harvest or grazing height and submit the whole part of the plant that will be ingested. Mix thoroughly to make one large composite sample.

Grains do not accumulate nitrate, so nitrate testing is not typically performed on grains.

Sample Storage and Shipment Guidelines

Place moist samples (fresh green grasses, silage) in plastic bags and place them immediately in a cooler on ice or ice packs. Keep these samples chilled or frozen until shipment, and ship them with ice packs. Place dry samples, such as relatively dry corn stalks and hay, in paper bags and keep them at room temperature until shipped; ice packs are not needed for shipment of dryer samples. Regardless, ship samples as soon as possible after collection to decrease the risk of reduced nitrate levels. Ship samples overnight, or deliver directly to the laboratory. Storing moist plant samples in plastic bags at room temperature will result in bacterial growth and reduced nitrate, resulting in inaccurate nitrate results.

Laboratory Submission Guidelines

Please see the UKVDL website to download the current accession form (see link for "Forms" on the homepage, and click the links for "New Standard Accession Form" as well as the "New Standard Accession Continuation Form" when sending multiple samples from one farm).

Visit for more information on nitrate issues. For nitrate questions, contact Cindy Gaskill, DVM, PhD, clinical toxicologist at the UKVDL at 859/257-7912 or

The University of Kentucky Veterinary Diagnostic Laboratory provided this information.

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