Forage Sample, It’s in Your Hands
Schroeder, NDSU Extension dairy specialist
Knowing the quality
of forage is paramount to pricing, whether you are buying or selling.
Hay sampling is probably the most important aspect of forage quality testing.
Accuracy is in the hands of the sampler.
When you think about
it, we expect a lot from very little. A pinkie-sized ground-up sample
weighing less than a gram must represent tons of hay from a variety of
fields. Once in the lab, this gram is sub-sampled from about a half-pound
of material provided by the sampler, so it is critical that the sample
given to the lab accurately represents the hay being tested. Whether the
sample accurately represents a stack is the responsibility of the sampler.
The lab can only test the sample presented to them!
Weather damage and
delayed harvest has had a significant effect on hay, especially alfalfa.
The proportion of protein and fiber of leaves and stems are very different
and influenced by harvest stage and conditions. To determine nutrient
quantity and quality, the sample of forage must represent the leaf to
stem ratio of the bales, as well as the weed composition of the hay. Both
can vary considerably across and between fields. Aside from supply and
demand issues, accurate analysis of forage can be the single greatest
determinant of price. Following proper protocols will help the sampler
obtain a fair, representative sample of the hay lot.
When these sampling
protocols are followed closely, different samplers can usually repeat
the lab measurements within a reasonable range. These protocols are fairly
universal, but they do vary slightly from region to region. Here are some
important steps and guidelines for taking alfalfa hay samples:
- Identify a single
lot of hay – Lots must be from the same cutting, variety and field.
They also must be at the same stage of maturity and harvested within
48 hours of each other. Do not mix lots. A lot must not exceed 150 to
200 tons. If you know of differences in quality, separate into different
- Choose a good,
sharp coring device - The coring device should have an inside diameter
on the cutting edge of at least 3/8 inch and no more than 5/8 inch.
The cutting edge should be at right angles to the shaft and kept sharp.
Dull probes will cause material to be pushed out of the core. Do not
use an open auger or corkscrew type device which selectively samples
leaf or stem parts.
- Sample at random
- Walk around the entire stack and sample bales at various heights to
the best of your ability. Do not avoid some bales or choose others;
sample at random. Try to obtain cores from as broad a group of bales
as possible within the stack.
- Take enough cores
- Per lot, sample a minimum of 20 bales (one core per bale). Take more
cores (20-40) in larger lots or if the hay is very variable.
- Use good technique
- Probe the ends of bales near the center and at least 12 to 18 inches
into the bale. The probe should be at a right angle to the bale end.
Do not slant the probe or sample from the sides.
- Handle samples
properly - Combine cored samples into a single sample and store it in
a sealed freezer bag. Do not expose the sample to heat or direct sun
and send it to the lab quickly. Moisture estimates are particularly
prone to change in the sample before it gets to the lab.
- Not too big, not
too small - The sample should weigh about a half pound (220 grams).
If you get a larger amount, the diameter of your probe may be too large.
Many labs will not grind a large sample, which defeats the purpose of
careful sampling. Too small a sample will not adequately represent the
- Split samples
correctly - If you want to test the performance of a lab, send a fully
ground and mixed sample to another lab. Never split an unground sample.
Reputable labs will return your ground sample to you for further testing
if you wish. (You should reject labs that are unwilling to do this).
Many disputes about
hay testing results can be attributed to differences in sampling methods.
The principle of hay sampling is to obtain randomly chosen samples, which
represent the average composition of the hay stack or lot. Never present
an un-cored sample to a lab such as a flake or a small handful of forage.
Research has shown
that, if these simple guidelines are followed, reliable results can be
obtained, even if you are using different probes or people. Nonetheless,
a minimum of +/- 0.5 percent variation in results is normal and should
be expected due to typical variations in sample and lab practices.
Schroeder, (701) 231-7663, email@example.com
Editor: Rich Mattern, (701) 231-6136, firstname.lastname@example.org