October 2007 Newsletter
Clair Thunes
the good suggestions of topics. I will do some research on the topics
of interest and include what I find in a future issue. Since I
started writing this Sacramento has had its first major rain and the
temperature dropped enough that I splurged and lit a log fire. Not
really necessary but I justified it as being a necessary test of the
chimney while it was still warm enough to open the windows if it
smoked really badly. It won’t be long until it really is colder at
night though and extra heating will be a necessity. What about your
horse though, log fires are definitely not allowed anywhere near
stables so how do horses stay warm? I’ll cover this in some detail
below along with a detailed look at omega-3 fatty acids.
Unfortunately I got a bit carried away with these two topics, there is
just so much information I want to share, so I’m going to hold off on
a couple of the pieces I was going to do this month. I will put them
in the November issue, meanwhile, I hope your winterizing is going
well.
Happy Halloween,
Clair
PS if you missed the September issue you can find it as a PDF file on
my website www.equilibrateequine.com under the “files and newsletters”
tab.
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IN THIS ISSUE:
How do horses thermo-regulate when it’s cold?
Fat composition demystified
What is so important about omega-3 fatty acids?
Flax
Visible signs of dehydration
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HOW DO HORSES THERMOREGULATE (MAINTAIN BODY TEMPERATURE) WHEN IT IS
COLD?
Horses are mammals and as such are warm-blooded just like humans and
so when the air around them is colder than their body temperature,
heat transfers from them to the environment and they get colder. To
survive they must regulate this heat loss, however such heat loss is
not always detrimental, for example if the horse is too hot and needs
to cool down. This is why horses are in danger of overheating when
worked in hot conditions. Their body temperature rises due to energy
released from exercise (or when it is very hot, heat absorbed from
their environment) and they need to move that heat to their
surrounding environment. They cannot do that though if the
surrounding environment is as warm as or warmer than they are. So the
environmental temperature and body temperature determine the extent to
which heat must be conserved. If the horse remains in its comfort
zone or “thermo neutral zone” little needs to be done to regulate
temperature. Once at the bottom of this comfort zone the horse
reaches its critical temperature and the body speeds up chemical
reactions within the body in order to burn more calories and to create
more body heat. This requires an increase in dietary energy intake,
if there are not enough calories in the diet to meet the additional
needs for maintaining body temperature the horse will utilize its body
energy reserves (fat). This deficit continues for too long body
condition will be compromised and the horse will lose weight. (See
September 2007 newsletter, Getting Ready for Winter for an explanation
of energy balance and body condition score). Exercise produces heat
from energy burned by muscles so moving is another way the horse has
to stay warm but the energy for movement has to come from somewhere,
either the diet or body energy reserves. This is one reason why
horses seem to run around more when the weather is cold. Muscle
contractions don’t just occur though as a result of the horse
physically changing locations they also occur as a result of
shivering. The energy produced from these muscle activities raises
the horse’s core temperature. Other sources of heat that don’t require
feed or body energy reserves are the sun and such things as heat
lamps.
There are of course also ways of conserving energy and heat in order
to stay warm. Just like us, horses can reduce the blood flow to their
extremities such as their ears, muzzle and legs. This is why it is
often said that to tell if a horse is cold one should touch its ears.
If you think you might use this as a barometer I suggest feeling them
when the horse is not cold so you can tell the difference. Trying to
figure out from the ears whether a horse is cold when the whole horse
is wet from standing in the rain for several hours is not as easy as
it sounds, everything just feels damp and often you wonder whether you
can’t feel any heat because you are cold as well! Also like us horses
can make their hair stand-up which is called piloerection (think of
goose bumps) which acts to increase their hair depth and traps air
next to their bodies creating an insulating layer. It is because of
this function that you might hear people say that well cared for
horses are quite alright out in the cold as long as it is dry. Once
their coats get wet the hair is unable to stand up and create this
insulating layer. They then rely on the oils in their coat to prevent
their skin from getting wet, which is why you should not bathe a horse
that lives out in the winter or use a body brush, they need the oils
to stay near their skin to act as a protective barrier. Horses living
outside need to have access to adequate shelter such as a 3 sided shed
as such shelter has been shown to reduce heat loss by 20% not only
because it allows their hair to stay dry but it also reduces heat loss
from wind chill. Before we get to wind chill I want to mention that
piloerection is also why some people do not believe in using blankets
and actually think blankets can cause a horse to be colder. This is
certainly true if the blankets do not contain adequate insulation for
weather conditions. A blanket flattens the horse’s hair and prevents
piloerection. If in turn the blanket is not thick enough to
adequately insulate or it leaks, the horse it will be cold and will
not be able to use piloerection to stay warm. This is not to say that
blankets should not be used, if you have a horse who does not carry
much weight, with a thin hair coat or decide to clip your horse
because it is in heavy work, a blanket will be necessary. A quick
word of caution against thinking that by bringing your horse into a
stable (box stall) during cold dry weather that it will be warmer,
this may be true but also consider that in a stable there is limited
space for movement, there are no other horses to huddle up with, air
is often still and cold, and there is less heat from sunlight
available. In my experience during such dry cold conditions, stables
(box stalls) are often colder than outside. Often the coldest part of
the night is around 6am, as the sun comes up areas reached by sunlight
warm up quickly compared to those areas still in shade such as the
inside of stall, so horses in stalls are subjected to cold for far
longer than those horses that can get out into the sun. This can
cause a real conundrum in spring and autumn when your stabled horses
are blanketed at night and you need to take their blankets off early
in the morning before you go to work because later in the day they
will be hot. In these instances you have to know your horse and know
whether it is better for them as an individual to be too hot or too
cold. The hard keeper who is lean, gets cold and is stressed easily
would probably be better left with the blanket on versus the horse
carrying more condition who won’t be at any great detriment if he is a
little chilly for a couple of hours.
The critical temperature mentioned earlier can be used to determine
what your horses nutritional requirements are relative to ambient
temperature, wind chill and wet hair coat. According to an article by
the University of Maine Cooperative Extension, “estimates for the
lower critical temperature (LCT) for horses are between 30 and 50
degrees Fahrenheit depending on hair coat, body condition, wetness and
windchill”. They go on to give the lower critical temperatures in
degrees Fahrenheit based on hair coat as follows, wet or short hair
60, moderate length hair coat 50, heavy coat 30. Once the average
temperature reaches the LCT human intervention is required such as
shelter, a blanket and or extra feed. In the last newsletter
(September 2007) in the “10 things to do now to prepare for winter” I
suggested making a plan on how you will keep track of the weather over
the winter in order to make good management decisions. This is
because you not only need to know if there is going to be a
significant drop in ambient temperature but also what the temperature
will be with wind chill, as movement of air across skin causes
increased heat loss. Sometimes you will see on weather forecasts a
temperature and then a “feels like” temperature. This is the
temperature accounting for wind chill. The National Weather Service
has a wind chill chart that shows for any given ambient temperature
and wind speed combination what the wind chill temperature will be.
For example when ambient temperature is 35 degrees Fahrenheit and wind
speed is 10mph wind chill temperature is 27 degrees Fahrenheit, and
when ambient temperature is 35 degrees Fahrenheit and wind speed is
25mph wind chill temperature is 23 degrees Fahrenheit. Water freezes
at 32 degrees Fahrenheit so without accounting for wind chill these
examples are above freezing, but with wind chill both drop the
temperature below freezing.
So how do you adapt your feeding regime to insure that your horse has
enough energy when the temperature drops? It is estimated that for
every 5 degree drop in temperature below the horses LCT an additional
1 Mcal/day are necessary which roughly equates to an additional 1 lbs
of grass hay. It is not only safest to make relatively quick changes
in diet through alterations in hay in order to avoid colic and
laminitis, but when we want to raise internal heat production,
increased hay consumption is best. Hay is digested by bacteria/
microbes in the horse’s cecum and large intestine and this microbial
fermentation actually produces heat which warms the horse from the
inside. If we think back to our 1100 lb horse from last month (who
we’ll call Bobby) he needed 16.7 Mcal/day for maintenance and if we
say that he has a medium hair coat and therefore a LCT of 50 degrees
Fahrenheit, then when the temperature drops to 40 degrees Fahrenheit,
Bobby will need 18.7 Mcal/day. Assuming 1 Mcal/lb of grass hay this
is a change from 16.7 lbs to 18.7lbs. Most horses will happily eat
2-2.5% of their body weight per day in dry matter if fed free choice
which for Bobby would be 22-27.5 lbs per day of hay. So a horse at
maintenance should easily be able to consume all the energy needed to
stay warm and maintain body condition from hay alone. However, if a
horse is working and needs energy not only for maintenance and warmth
but also work, then the energy requirement will be greater and it may
not be possible to meet this need from hay alone although as much of
the need as possible should be met from hay for the reasons previously
mentioned. If you follow the weather forecast and know a storm is
coming and what the expected temperature will be it is relatively
straight forward to make the necessary changes in hay intake
necessary. Ideally these changes should be made in the 24 hours
leading up to the expected lower temperature and maintained throughout
the cold spell.
Horses do adapt to cold over time, according to Dr Cymbaluk of the
ministry of Agriculture, Food and Rural Affairs in Ontario Canada,
horses typically require a 10-21 day adaptation period. A horse’s
ability to adapt depends on the duration of the cold weather and the
horse’s energy intake. A horse isn’t going to be able to adapt to a
sudden winter storm and will require more intervention. However,
energy intake is more critical. Well fed horses adapt better than
those who are underfed. Adaptation should be considered when
contemplating a horse’s lower critical temperature. A horse who has
spent a good amount of time in Arizona where the average summer high
is around 95 degrees Fahrenheit and average winter low is around 55
degrees Fahrenheit may hit its lower critical temperature at a
relatively higher temperature than a horse who lives in Maine where
the average summer high is only around 70 degrees Fahrenheit but the
average winter low is around 20 degrees Fahrenheit. For the horse
from Arizona the lower critical temperature may be 60 degrees even
with thick haircoat. The age of the horse is also worth considering.
Older horses are generally less efficient at both digestion and
thermoregulation and so are more susceptible to extremes in
temperature. They will therefore need a diet that is more easily
digestible and may require intervention earlier than their younger
counterparts to stay warm. Young horses especially those under a year
of age are also less able to handle cold weather in part due to the
large amounts of energy that are being utilized for growth. They
should be provided with good shelter and ample access to good quality
hay.
Your horse will tell you if he/she is cold, pay attention to the
warning signs and make adjustments to hay intake and overall
management as necessary to a insure that your horse comes out of the
winter in good condition.
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FAT COMPOSITION DEMYSTIFIED – WHAT IS THE DIFFERENCE BETWEEN
SATURATED, UNSATURATED AND POLYUNSATURATED FAT (FATTY ACID) MEAN?
Fats are made up of fatty acids which contain chains of carbon atoms
that have branches coming off the chain. The branches are made up of
hydrogen and oxygen atoms. The chains of carbon can vary in length
from a 2 carbon chain fat, to upwards of 30 carbons. Carbon atoms
(chemical symbol C) have space for 4 bonds or “docking stations” that
they can use to attach to other atoms. Carbon atoms may be joined to
each other by either single or double bonds i.e. either using one (C-
C) or two of these docking stations (C=C). We hear all the time about
saturated and unsaturated fats, and the difference between these two
is that in saturated fats, all of the carbons are held together in the
chain by single bonds (C-C). In unsaturated fats one or more of the
carbons in the chain are held together with a double bond (C=C). If
they have more than one of these double bond connections they are
called a polyunsaturated fatty acids (PUFA’s).
Fats are used for all sorts of functions within the body, for example
cell membranes and absorption of fat soluble vitamins. Like us the
horse can make a lot of the different fats it needs by taking fat
provided in the diet and combining it to components taken from
proteins and carbohydrates to make a new fat. However, the horse can
only make saturated fats (those with single bonded carbon chains)
because it lacks the enzymes necessary to make/insert double bonds
into the carbon chain. For some body functions unsaturated fats are
required, especially the polyunsaturated fats which can not be created
from other dietary components. Therefore certain polyunsaturated fats
are known as Essential Fatty Acids (EFA’s). The most important of
these EFA’s are linolenic and arachidonic acids (both omega-6 fatty
acids) and linoleic acids (an omega-3 fatty acid). For those who are
wondering, the omega-3 and omega-6 notation refers to where the double
carbon bonds are in the chain.
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WHAT IS SO IMPORTANT ABOUT OMEGA-3 FATTY ACIDS?
As I’m sure many of you are aware, there has been a lot of interest
recently in the health benefits of supplementing Omega-3 fatty acids
in human diets and there is also interest in feeding them to horses.
When human diets are supplemented with foods high in omega-3 these
omega-3 fatty acids replace some of the omega-6 fatty acids in cell
membranes and in particular archidonic acid. This is important
because arachidonic acid is a precursor for inflammatory response. So
if there is less arachidonic acid there is less potential for
inflammation. In humans, consuming more omega-3 fatty acids has been
shown to reduce pain perception along with the rate of degenerative
disease development such as arthritis. This year in the nutrient
requirements for horses, the national research council states that
“data from studies where horses were fed diets enriched with omega-3
fatty acids (flaxseed and fish oils) have demonstrated modulation of
inflammatory mediator synthesis by cells taken from blood, peritoneal
fluid, or respiratory secretions. “ The physiological importance of
these findings is still unclear, but feeding increased levels of
omega-3 fatty acids may alleviate or even prevent inflammatory
conditions such as arthritis and recurrent airway obstruction. With
so much interest in the equine market place for joint supplements, I
am sure that this is an area that will receive a lot more research in
the near future.
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FLAX
So what if you would like try increasing your horse's omega-3 fatty
acid intake? As was mentioned earlier, flax seed oil is a great
source of omega-3 fatty acids, as are canola and walnut oils.
However, these oils are expensive as they are unstable and require
specialist extraction procedures. Not only that but they react to
heat and light so have to be stored refrigerated in the dark. Not
very practical for use in a horse barn! Flaxseed contains the highest
level of omega-3 fatty acid and it can be fed in the seed form and is
therefore the easiest way to supplement a horse’s omega-3 fatty acid
intake. Flax seed can be added to the horses diet either fed ground
or whole, whole is certainly less work. As nice benefit of feeding
flax is that it contains a substance called mucilage which when wet
creates slime like snot. Pretty gross sounding but it is a great
lubricant and may help keep feed moving through the digestive tract
therefore reducing the risk of impaction colic. Over the colder
months when horses often reduce their water intake and therefore
increase their risk of impaction colic, feeding flaxseed could be a
little insurance policy. Feeding 2 to 4 ounces (about a cup) of
whole flaxseed daily will contribute to improvements in hoof, coat,
and skin condition as well as speed up the rate of recovery from
injury and arthritic conditions. You can use it in place of the
vegetable oil that so many people use to improve coat condition.
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VISIBLE SIGNS OF DEHYDRATION
We all think about dehydration in summer when the weather is hot and
horses fluid and electrolytes through sweat. However, how often do we
think about dehydration in winter? Dehydration occurs when the
horse’s water intake is less than the water lost through bodily
functions. Water is not just lost as sweat, but as urine, in feces
and even when breathing. In the winter when the weather is cold
horses sometimes will not drink as much as they should and access to
pasture is often limited. (Pasture grasses contain water and in
winter are often wet from precipitation). Dehydration can be very
serious as it can result in other secondary conditions such as
compaction colic, kidney problems and normal cell function may become
inhibited. This is why it is important in very cold weather to offer
horses water that has been warmed above freezing and to keep track of
overall water intake. This can be hard if you are using automatic
waterers. While buckets/tubs that require manual filling seem like a
lot of work, they truly are the only way to know how much your horse
is drinking. Research has shown that horses kept in cool ambient
temperatures with access to near freezing water drank 38-41% less than
water heated to an average temperature of 19 degrees Celsius. Other
ways to avoid winter dehydration include feeding grain in a soup by
adding water to the grain, feeding soaked beet pulp, mashes etc all of
which help increase your horse’s water intake. Soaking hay so that it
is eaten wet is a great way of getting water into your horse but may
not be an option in very cold climates. One of the first signs of
dehydration is a reduction of dry feed intake so if you notice your
horse suddenly starts to leave, or be less interested in hay you might
want to consider checking for dehydration. Other signs of dehydration
in the horse are similar to those in the human; reduced physical
activity, lethargy, impairment of physical activity, and reduced urine
fluid resulting in darker stronger smelling urine. The classic test
for dehydration is the skin pinch test. This is best performed by
pinching a fold of the horse’s skin over the horse’s shoulder. When
released the skin should spring back to its fattened position. At
less than 5% dehydration physical symptoms may not be visible but at
6% you may notice a slight inelasticity in the skin so that it remains
in a pinched position for longer than 1 second. Once 8% dehydration
is reached there is definite skin inelasticity and capillary refill
time is 2 to 3 seconds (if you push on the horse’s gums with your
finger, this is the time it takes for the color to return to the gum
once you remove your finger), mucous membranes may feel dry, feces
will be dry and urine will be reduced, so if you are lucky enough to
muck your own stalls pay attention to the consistency of the feces and
whether there seems to be less wet bedding than usual. If you believe
your horse may be dehydrated call your veterinarian as they may need
to administer intravenous fluids. For example a 500 kg horse that is
8% dehydrated will require approximately 40 liters of fluid to
rehydrate and if you are unsuccessful in getting your horse to drink
what is needed other intervention will be required. Knowing what is
normal for your horse is imperative so that you can catch something
like dehydration before it becomes something more serious.
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NEXT ISSUE:
Should you be feeding more or less feed this winter?
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Services offered by Equilibrate Equine Consulting include phone
consultations on both nutrition and management issues, hay sampling
and interpretation, ration balancing, custom vitamin and mineral mixes
and packages for ongoing care. For more information please visit
www.equilibrateequine.com or email in...@equilibrateequine.com