HAY QUALITY TESTING: WHAT DOES IT MEAN?
Recognizing
quality differences is important to both producers and buyers of hay. Research and experience show that combining
visual inspection with chemical analysis greatly improves your accuracy
when you predict the nutritive value of hay. But
what do those numbers on the hay test report mean?
A
chemical analysis is valid only to the extent that the sample truly
represents the stack or lot of hay under consideration. Use
of a core sampler to get that representative sample is essential. Commercial
forage samplers are available through farm supply sources. Many
county Extension agents have a core sampler to borrow.
A
lot of hay should represent hay harvested from the same field, the
same cutting, and the same stage of maturity. If
two lots of hay are in a stack, sample them separately. Bales within a lot of hay should be sampled at random. A minimum
of 20 core samples are recommended for a lot of 10 tons or more.
To
promote common methods of hay testing and reporting, a standardized
test has been developed. The
common analyses found on many hay test results include dry matter,
crude protein, acid detergent fiber, neutral detergent fiber, calculated
total digestible nutrients and relative feed value and the minerals
calcium and phosphorus.
Dry
matter (DM). At
the time of baling, moisture content may range from 10 to 25% (90
to 75% dry matter). Usually hay test results will be reported
on an as-fed basis and on a 100% dry matter basis. This puts all hay on a common basis for comparing feed values
of hays with different moisture contents.
Crude
protein (CP). The
quality of hay is closely related
to its crude protein content,
since it’s related to stage of
maturity and leafiness. Hay
high in protein allows the livestock producer to save money by reducing
the need for higher cost protein concentrates in the ration.
Acid
detergent fiber (ADF). Hay
quality is also related to its energy content. This
test result indicates the available energy in hay. ADF is the plant fiber that remains after an acid detergent
removes part of the digestible cell wall material and the cell contents. ADF has a negative correlation with digestible
energy (DE); that is, as ADF increases, digestible energy decreases.
Neutral
detergent fiber (NDF). This
is the plant fiber that remains after a neutral detergent is used
to remove cell contents in the testing lab. NDF
has a negative correlation with feed intake; as NDF increases, feed
intake decreases.
Total
digestible nutrients (TDN). This
has been the most extensively used measure of feed quality in the
United States. It is
the sum total of all digestible
organic nutrients – proteins,
nitrogen-free extract (plant
cell contents), fiber, and
fat. TDN
is most often estimated and calculated from a single fiber test,
such as ADF.
Relative
feed value (RFV). This
estimate of overall forage quality is calculated from estimates of
intake (from NDF) and digestibility (from ADF) of forages on a dry-matter
basis.
The
test results for the minerals calcium and phosphorus are needed for
the feeder of hay to develop a ration with the proper balance of calcium
and phosphorus. This is
usually in the 1:1 to 2:1 range.
Livestock
producers recognize the value of high-quality hay. When you use high-quality hay, you reduce the quantity of
supplement that you must feed. The
increased palatability of high-quality hay also results in greater
consumption. It costs the hay grower more to produce
high-quality hay. Thus
livestock feeders should expect to compensate those growers who are
willing to produce high-quality hay.
For
more information on hay testing, refer
to PNW223, “Testing the
Quality of Alfalfa Hay” by D. B. Hannaway and P.J. Ballerstedt. Contact Idaho, Oregon and Washington Extension offices to
get a copy.
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