As I travel around the world, learning and teaching people about
feeding horses with laminitis, I keep hearing a recommendation
that has never made sense.
People say that leaving
hay in a shed for a year renders it ‘safe’ for horses
with laminitis. You will commonly hear cattle producers say that
the nutrient content of hay changes after ‘going through
the sweating period’.
This is true in a certain
context, but the changes that occur happen in the first month,
and only apply to hay baled above 20% moisture. (Coblentz, 1996)
In many humid regions it is common to put up cow hay wetter, realizing
it may heat up, and mold slightly; but some mold on hay is generally
safe for cows.
Many horse people who
hear this advice assume that hay must stay in the stack at least
a month before a hay sample can be pulled for analysis. This is
not true in most cases for horse hay, which should be baled when
it is between 12-15% moisture to prevent formation of mold. It
is true that hay loses vitamins A and E after a year in storage.
Perhaps this can be construed as ‘loss of nutrients’
if using very general terms, but depletion of vitamins
will not prevent laminitis or obesity, which is caused
by excess sugar and calories.
Forage researchers have shown that when hay moisture is below
about 40%, the enzymes that control respiration stop, so sugar
can’t be lost through respiratory mechanisms. If hay is
kept dry, sugar can’t leach out. Yeast, mold, and bacteria
would eat sugar in hay baled above 18% moisture, but mold would
also be present; since horses should not eat moldy hay, so baling
wet is not a viable solution.
There is no mechanism which explains how sugar, or any other nutrients
that are routinely tested in forage, would just disappear in properly
harvested and stored hay.
While searching for the source of this myth, it was brought to
my attention that in a 1966 edition of the Pony Club manual, a
recommendation is given to feed ponies ‘old seed hay,
preferably 12 to 18 months in the stack’.
Also: ‘Good old hay provides excellent keep for small
stabled ponies’. While I value Pony Club advice for
many things, it might be best to get advice for feeding laminitic
ponies elsewhere. All this conflicting information needs to be
put in the proper context of buying hay for horses that must have
sugar and calories reduced.
Procedure:
A study was conducted
in southern Colorado, where low humidity (20-30% RH) is common.
Three lots of hay were selected; one 100% Italian ryegrass, one
approx 75% alfalfa/ 25% brome/orchard grass mix, and one 100%
alfalfa. Alfalfa bales were purposely selected from an area of
the field that were shaded in the afternoon and had higher moisture.
All were tested immediately after baling with a moisture probe,
and 6 bales of each lot were placed in a hay shed on a pallet.
A Penn State forage sampler was used to obtain one core per bale
on the day of baling, and at 2 weeks, 2 months, 6 months, and
9 months. An additional sample of the alfalfa/grass mix was taken
at 13 months.
The 6 cores were well mixed in a clean plastic bucket, and were
sent to the lab with no sub-sampling. Cores were made in a different
quadrant of the bale at each sampling to minimize any possible
affect of additional air contact.
Results:
The Italian ryegrass
averaged 8 % moisture, the alfalfa/grass mix was 12 %, and the
pure alfalfa was 20% moisture immediately after baling. The %
moisture on the alfalfa baled at high moisture decreased rapidly
due to dry storage conditions and air flow around the bales. No
mold was noticeably by sight or smell and the color remained bright
in all samples throughout the year of the study.
The variation in test
results on a dry matter basis for Crude Protein, ADF, NDF, NFC,
starch, Water Soluble Carbs, Ethanol Soluble Carbs, Ca, P, Mg,
K, Na, Fe, Zn, Cu, Mn, Mo, and Digestible Energy were
not greater than would be expected from testing error as per Dairy
One Forage Testing Lab manager. (Link to table)
Some test results on some sampling dates were slight higher than
previous, and some were slightly lower than previous. Since it
is impossible for nutrient concentration on a dry matter basis
to increase in baled hay, we must also assume the slight reduction
in results were from inherent sampling and testing error.
Discussion:
Much of the knowledge and advice given regarding hay may apply
to cow hay, but may not apply to horse hay. Previous
work showing nutrient loss in stored hay shows that dry matter
loss is closely related to initial moisture content of hay at
baling. (Buckmaster) Hay baled at over 20% moisture can undergo
chemical changes generating heat which raises temperature enough
to bind protein to carbohydrates making the protein indigestible;
the reaction is called the Maillard reaction. This may be compared
to the formation of caramel when sugar and milk are heated together.
Hay that has been changed this way will be brown, just
like caramel. Horse owners generally avoid brown hay, so this
reaction should not be of significance when purchasing hay for
horses.
Carbohydrate loss may also occur when mold feeds on the hay. Again,
horse owners know better than to buy hay that is moldy, because
horses cannot tolerate moldy hay like cows can. Hay baled between
12-15 % moisture, which should be the target for good quality
horse hay, will not heat up, should not mold if stored properly
and therefore will not change in quality from the time it is baled
for several years if stored in a dry barn or shed in an arid environment.
In some very humid climates, such as the United Kingdom, the southern
United States, or some tropical regions, it may be nearly impossible
to bale and store hay at less than 12% moisture. The stable moisture
content of baled and stacked hay will be dependent on ambient
humidity. Under these difficult conditions, horse owners may assume
that brownish, slightly musty hay is the best they can get. If
hay is baled at over 15% moisture, heating and molding may occur,
resulting in loss of nutrients. Horse owners should not purchase
or test such hay until the heating period is over and the extent
of the damage is known. It’s not so much a case of waiting
to see how much the nutrients have changed, but waiting to see
if it will be fit to purchase at all for horse feed. Even when
baled too wet, once the heating period is over and the hay has
dried down in the stack, which should occur within a month, loss
of protein, carbohydrates and minerals stops. Only high amounts
of continually growing mold would lower the nutrient content after
this period. When stored away from rain and high humidity, nutritional
content of hay does not change over a couple of years except for
fragile vitamins.
Summary:
No nutrients quantifiable
by hay analysis are lost during 9-13 months of storage in hay
that is baled between 12-15% moisture and properly stored in a
dry climate. There is no advantage to purchasing year
old hay for horses with lower nutritional requirements.
Buckmaster, D.R., Indoor Hay Storage: Dry Matter Loss and Quality
Changes, factsheet PSU/92M, Penn State University http://www.age.psu.edu/extension/factsheets/i/i102.pdf
Coblentz W. K., J. O. Fritz, K. K. Bolson, and R. C. Cochran,
Quality Changes in Alfalfa Hay During Storage in Bales. 1996.
J. Dairy Sci. 79:873-885
For more articles by Kathryn Watts on managing horses with laminitis,
go to www.safergrass.org
