MANHATTAN, Kan. - Unpredictable precipitation and seasonal quality make stored feed vulnerable to a variety of conditions including toxins and harmful agents.
Drought conditions make forages more susceptible to prussic acid or nitrate poisoning. Drought stunted crops can accumulate cyanide and build toxic levels of prussic acid. Running a nutrient analysis, from good samples taken by producers, is the only way to establish the feeding value, say officials at Kansas State University."A forage analysis can be no better than the sample submitted,"said Gerry Kuhl, K-State Research and Extension feedlot specialist. "It is key to get a good sample to get good results."
Preparing samples takes a conscientious effort to ensure an equal distribution. Collections should be a representative sample of the forage lot, said Dale Blasi, Extension beef specialist.
According to Blasi, a forage lot consists of forage harvested from one field at the same cutting with similar forage type, variety, weed infestation, type of harvest equipment, weather during growth and storage conditions.
Specific methods for gathering a representative sample vary for each type of feed.
Baled Hay - Core samples from 15-20 randomly selected bales should be gathered. If the bales are fed in succession of their cutting times in the season, each cutting should be analyzed. If a mixture of cuttings will be fed, test a proportional number of bales from each set.
"Many commercial hay probes are available on the market and range considerably in price," Blasi said. "If the purchase of one is not an option, many county Extension offices have forage probes available for use."
To sample baled hay without the aid of a forage sampler, remove a small section from each bale and cut the hay into three-inch lengths with shears.
Loose Hay - Remove a handful of hay from 15-20 positions for each lot. Save all leafy material belonging to the sample. Cut into three-inch lengths, mix and send a representative sample to the laboratory.
Pasture - Pasture sampling is more difficult due to fertility and moisture differences. Sample by clipping 8-10 random locations across the field.
"Walk in a zig-zag line across the field and try to get a cross-section of all species for the sample," Kuhl said. "More is better."
Remove the forage from a square foot area at grazing height. Mix all the collected forage to get a sample.
Field Forage Crops - Remove plants at normal harvesting heights at eight to 10 locations in the field. Chop into one- to two-inch pieces, mix and remove a sample.
"In most plants, the lower third of the stalk or stem holds over 70 percent of the nitrates," Kuhl said. "Producers can test these portions of the plant separately to find if the feed is safe by taking two samples; one from the top two-thirds of the plant, and a second from the lower stalks."
Silage - Samples should represent several locations across the silo face to insure representation. A silo should be sampled more than once during the feeding period, especially if multiple forage fields are represented.
Grain in Bin - Use a grain probe to obtain the sample. If one is not available, random grab-samples from 10-15 areas of the bin can be mixed for a sample.
Kuhl said to allow time for test results to be returned for formulation of a ration or supplement needs. As a general rule, allow one to two weeks for results of the analysis. To speed turnaround, most labs will fax or email results.
Submit forage samples to an accredited laboratory of the National Forage Testing Association. Depending upon the nutrients being tested, a forage analysis will cost around $12 and higher.
Additional pointers for obtaining quality samples can be found at http://www.oznet.ksu.edu./forage/pubs/97notebook/fora36.pdf.
Proper handling of the sample from the farm to the laboratory insures best results. General rules include:
1. Sample size should be a minimum of one quart. Be sure the sample is representative. All forages should be chopped to a length of three inches or less to make handling easier.
2. Pack tightly to exclude air. Seal airtight. Use plastic bags in all cases, except very dry samples.
3. Send samples to the laboratory as quickly as possible. Indicate requested analysis with the appropriate form.
4. All letters, instructions or payments should be put in a first class mail envelope and attached to the mailing container. The sample container can go as fourth class mail. Address both letter and sample container with correct laboratory address and your return address.
USDA and University of Missouri Cooperative Extension Service