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Nutrition for Rehabilitating the Starved Horse |
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It is difficult to comprehend the long-term
neglect and surrounding situation that produce such a devastated, depressed
creature as a starved horse. The bones are so prominent that the skeleton
appears to belong to a larger horse, the head is disproportionately large
compared with the body, and the tail is always low and motionless. But the
low hanging head tells it all. The ears barely move to any sounds in the
environment, no extra energy is spent interacting with herd mates. The eyes
are dull, without expression, without expectations.
Researchers from the UC Davis Center for Equine Health conducted a survey to
assess the prevalence of starved horses in California and found the results
quite disturbing. Among the responders to the survey were animal control and
humane society organizations in 36 counties, with an estimated equine
population of 1,041,560. Of this number, 2,177 horses were found to be
severely malnourished. The most common reason for these cases was owner
ignorance, followed by economic hardship.
A research team comprised of Dr. Carolyn Stull (UC Davis
Veterinary Medicine Extension), Dr. Anne Rodiek (California State
University, Fresno), Dr. Christine Witham (private clinician), Dr. Pamela
Hullinger (California Department of Food and Agriculture), and Kelly Weaver
(UC Davis Veterinary Medicine Extension) has been studying the problem.
Funded in part by Purina Mills, Inc., the study provides a standard body
condition scoring system to
assess the weight status of a horse and compares different diets for
refeeding the malnourished horse. In both humans and horses, abrupt
refeeding can cause dysfunction of the body's metabolic systems, which can
lead to failure of the heart and lungs and ultimately to death. The goal of
this research is to provide new information and guidelines for recognizing
and treating malnourished horses.
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| This horse has a body condition score of three. The
ribs can be observed easily, even with the horse's winter coat, the tail
head is prominent and can be felt easily, and the hip bones are rounded
and protruding. (above and below right). Note the dip in the
withers in front toward the neck and behind toward the back, exhibiting
little or no fat deposit around this area. |
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| At left,
the hip shows an inverted V shape with the spine at the apex,
representing a lack of fat deposition |
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What Happens During Starvation
During the starvation process, the horse initially uses
any fat and carbohydrate stores in his body to supply energy for metabolism.
This is the normal process for any healthy horse: fat and carbohydrates are
used for energy, exercise, brain function, circulation, etc., and are then
replaced with nutrients from food. The cycle is constant and never-ending,
even during sleep. In a starved animal, once this source of fat and
carbohydrate is gone, energy is derived from the breakdown of protein. While
protein is a component of every tissue, there are no inert stores of it in
the body such as there are for fat and carbohydrates. Consequently, the
starved body uses protein not only from muscles, but also from vital tissues
such as the heart and even gastrointestinal tissues-tissue that is necessary
for life. The starved body cannot select which tissue protein will be
metabolized for energy. As time goes by, the horse's survival is in a
precarious situation. When a horse loses more than 50% of its body weight,
the prognosis for survival is extremely poor.
The Refeeding Problem
Refeeding starved animals, including humans, is not an
easy process. In humans suffering from starvation caused by illnesses such
as anorexia, cancer, or gastrointestinal obstruction, patients can develop "refeeding"
syndrome when they are given concentrated calories, and this in turn can
lead to heart, respiratory, and kidney failure usually 3 to 5 days after the
initial meal. This same syndrome has been reported in the literature for
horses. Thus, our research team wanted to develop a refeeding program for
horses that would minimize these effects and enable the horse to return back
to normal body weight. Our goals were to test feeds that were commonly
available and used in horse rations, so the refeeding program could be
implemented easily in any area of the country.
Experimental Diets for Refeeding
We selected three types of feed that were very different
in nutrient composition: alfalfa hay, oat hay, and a commercially available
complete feed consisting of grain, molasses, fat, and alfalfa. Alfalfa is
known to be high in protein (20%) but low in carbohydrate starch (3%). Oat
hay is high in fiber but low in protein (7%). The complete feed represented
a feed high in carbohydrate concentration, with 19% starch. The three types
of feed were given to 22 starved horses that were brought to the UC Davis
research site as representative of horses rescued by equine organizations.
Horses were fed one of the three diets over a 10-day rehabilitation period.
The researchers focused on this time period as critical to successfully
transitioning the gut from a starved state to a fed state. Even though the
diets were different in composition, they were fed in amounts that were
equivalent on a caloric basis, so that horses assigned the oat hay diet, for
example, received the largest volume of feed, while the horses on the
complete feed received the smallest amount but the same number of calories
at each meal.
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| This horse has a body condition score of five (above).
She appears very smooth, with no skeletal prominence. Her neck and
withers blend smoothly into her shoulders. Ribs do not show, and the
loin and hip are nicely rounded. |
| Right, this horse has a score
of nine. Note the obvious crease from his spine sunk between fat
deposits on either side. |
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Which Diet Worked Best?
Our results with the complete feed were very consistent
with human studies conducted 20 years earlier using concentrated calories.
As the horse ate the high-carbohydrate diet, insulin was released in
response to the high level of starch. The job of the hormone insulin is to
store the carbohydrate in cells for future energy use, but it also
simultaneously draws the electrolytes phosphorous and magnesium from
circulation into the cell. Since the starved horse has no stores of
electrolytes, this depletion may lead to kidney, heart, and respiratory
failure. These effects do not occur with the initial meal but usually
several days to a week later due to the repetition of insulin release
following a high-carbohydrate meal and the cumulative depletion of
electrolytes. The oat hay diet was very bulky and caused diarrhea in several
horses. Several essential nutrients such as phosphorous and magnesium were
low in the oat hay compared with the other diets; thus, this diet did not
support a successful rehabilitation. The alfalfa had the best results due to
its high composition of quality protein, but also the major electrolytes,
phosphorus and magnesium. Since alfalfa hay is very low in carbohydrate
content, there were minimal effects due to insulin response.
In a subsequent feeding study, we compared an alfalfa hay
diet to a diet of combination alfalfa hay and corn oil. Equine diets usually
do not contain much fat, but in recent years the use of corn oil to increase
the energy density of a meal has been widely used in nutrition programs for
older horses and in horses undergoing intensive training programs. The two
diets were fed again on an equal-calorie basis. Although the corn oil had no
harmful effects, substituting calories from corn oil for alfalfa decreased
the total nutrient content of phosphorous and magnesium in the diet. Thus,
the response to the diet combining corn oil and alfalfa showed a decreasing
blood phosphorous level over the 10-day period, which was not advantageous
to the rehabilitation. Again, the alfalfa diet was the most effective at
delivering the necessary nutrients in the correct amounts to the starved
horse.
Our research showed that starved horses had very different
responses to several diets. We found that the best approach for initial
refeeding of the starved horse consists of frequent small amounts of
high-quality alfalfa. This amount should be increased slowly at each meal
and the number of feedings decreased gradually over 10 days. After 10 days
to 2 weeks, horses can be fed as much as they will eat. The horse will show
signs of increased energy after about two weeks. Ears, eyes and head
movement will be the first noticeable movements. Some weight gain can be
achieved in one month, but three to five months usually are needed to
rehabilitate back to a normal body weight. Veterinary care and nutritional
advice should be sought as complications can arise. |
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