> Folks, I don't think you're talking about "fat" here. I think you're talking
> about muscle cells full of glycogen (and the water necessary to store it.)
> Fat is adipose tissue, stored under the skin and around the liver.
> Subcutaneous fat is easily measured with ultrasound scanning.
Hi Tom and everyone else,
I agree that a well-fed horse also has additional glycogen and water,
but no, the body condition scoring does not look at muscle, it IS BODY
(SUBCU) FAT. To be accurate, you have to look and FEEL for the fat and
look specifically in the places where muscle doesn't develop as
much---around the tailhead, along the ribs, withers, beneath the tail in
the "twist", along the spine, etc. It's not difficult to feel a horse's
cresty neck and know whether that's muscle or fat. The system is
consistent whether the horse is muscled or not, although it is easier in
an unfit horse beccause then you don't have to differentiate between
muscle and adipose tissue. The system was developed by Henneke at Texas
A & M some years ago and has been very well validated by ultra sound
measurements in many, many studies in fit, unfit, all types of horses.
I agree that doing ultrasound measurements is more accurate, but
logistically, it doesn't work in the field. If you have 220-250 horses
going through a vet check area within a few hours, they're not going to
stand around waiting for you to ultrasound the horse. I can body
condition score a horse---accurately---in less than a minute and catch
90% of the horses. If I tried to ultrasound them, as Lawrence et al did
the the Purina ROC in 1990, I would have been lucky to measure 30 or
forty of them, which is not a statistically viable sample population.
It's important to realize that because a horse is carrying some body fat
doesn't make him "fat". A horse carrying around 75 pounds of fat on him
is only carrying 7.5% body fat, the rough equivalent of a world-class
marathon runner. Horses (and the majority of animals) will deposit body
fat in the abdomen surrounding the intestines and the liver before they
start to deposit fat in any great quantities under the skin, so a horse
with a moderate amount of finish will already have some fat deposited
within the abdomen. However, there does seem to be a strong indication
that observable body fat under the skin needs to be present before the
horse enters the "optimum window of fatness" that I observed in my
project.
Susan Evans
California State Polytechnic University