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Forage
crop agronomists and animal nutritionists often bring up the topic of
forage quality. In the course of discussing this important subject, the
idea of taking core samples from various lots of hay and subsequently
having the samples analyzed in a laboratory to assess forage quality is
typically mentioned as well. Yet it is clear that many livestock
producers don’t regularly test their hay, but instead simply rely on
their ability to judge it by examining it. This raises a question about
the value of sensory evaluation of hay.
Actually,
much can be learned from a careful sensory examination of hay. First,
the plant species present can be determined. Does the hay consist
almost exclusively of a particular forage crop? Does the forage crop
tend to be higher in quality than other forages? Does the hay contain
weeds? If so, what percentage are weeds, and how much nutritional
benefit do they provide to livestock? Could the weed species in the hay
be toxic? The maturity of the hay, which one of the main factors
determining forage quality, can be visually assessed. The number and
maturity of seed heads and blooms, and the stiffness and fibrousness of
the stems are indicators of plant maturity.
Leafiness
is particularly important, because the higher the leaf content, the
higher the forage quality. Leafiness can be affected by plant species,
by stage of maturity at harvest, and (especially in legume hays) by
handling that results in leaf loss.
Texture
is a consideration. Softness usually results from early cutting, high
leaf content, and a suitable moisture level at baling. When hay is
"very soft" and pliable, it is difficult to distinguish
between stems and leaves just by feeling the hay. "Soft" hay
is soft to the touch, but stems can be detected easily. "Slightly
harsh" hay has stems that are a little rough. "Harsh or
brittle" hay is dry, stemmy, and unpleasant to the touch.
"Extremely harsh" hay can injure an animal’s mouth, thus
lowering intake.
Color
alone is not a good indicator of forage quality, but it can be an
indicator of harvest and storage conditions. A bright green color
suggests that hay was cured quickly and protected during storage. Slow
curing prolongs plant respiration, which reduces forage quality. Hay
that is rain damaged after being partially dried will lose color due to
bleaching. Mold growth on leaves and stems or exposure to sunlight will
also bleach hay. Baling at moisture contents at or above 20 to 25% may
cause high bale temperatures that result in tan to brown or black colors
(commonly called "tobacco hay").
A
pleasant odor indicates hay was cured properly. Moldy, musty
odors may occur in hay stored at moisture contents above 16 to 18%
(above 14% for 1-ton square bales). Animals may respond to off-odors by
going off feed. Odors caused by heating (>125°F) result from hay
being baled at too high a moisture content or from ensiling forage that
is too dry. Interestingly, hay with a slightly caramelized odor is often
quite palatable to livestock, even though the quality is reduced. If hay
has an odor similar to silage, it can indicate good or bad fermentation;
if it smells butyric acid (similar to rancid butter) it may lack
palatability, and low animal intake is likely.
Dusty
hay is usually the result of soil being thrown into the hay by rake
teeth hitting the soil. The presence or absence of molds, dust, and odor
are referred to as organoleptic qualities.
Visual
inspection can also detect foreign matter (anything that has
little or no feed value). Tools, sticks, rocks, wire, items of clothing,
dead animals, and cow chips have all been found in hay and are obviously
undesirable. Dead animals in hay can cause botulism, a deadly disease
that can kill farm animals. |
