Page 64 - August 2015

As environmental conditions change moving into winter, a foal’s body begins to conserve energy to keep warm and to build a winter coat, and there is less energy put toward growth. This is the time to counterbalance any negative effects of the foal’s first winter with good quality hay.
want large deviations in the short-term patterns. We don’t want the young horse to drop off in growth at weaning, for instance,” he says.
“Depending on the breed and objectives
of the owners, foals are weaned as young as 3 months of age and as old as 9 months. There are numerous variables to consider, but one
of the most important is the environment in which you are weaning the foal. If a January foal is weaned in the middle of a hot summer when pasture conditions are poor, this may have a negative impact on growth. By contrast, an April-born foal weaned in early fall when pasture may be re-growing will likely continue a strong pattern of growth,” he says.
By 6 months of age, a considerable portion of the foal’s diet is already provided by pasture. “The manager needs to pay attention to the horses and the environment, and consider
how best to fit the horse to its environment to optimize health and performance. We still see
a decrease in growth during weaning because the animals are stressed, and though conditions for forage in October may be good, from that point on the pasture quality declines as we move into winter,” he says. Environmental conditions change and the foal’s body starts to conserve energy for thermal regulation to keep warm
and for building a winter hair coat. There’s not as much energy put toward growth. It’s getting colder, pastures are declining in quality, and all signals to the animal are that the environment is changing and it needs to get ready for winter.
“In all the growth data I’ve looked at, there’s a decrease in growth rates during winter months, with February usually
being the lowest for horses raised in the northern hemisphere,” says Staniar. “The young horse’s body is conserving energy for other purposes and decreasing growth rate. But, the decrease at this time represents an opportunity for managers. If you realize this will occur, you can provide the animal with more energy and an environment that doesn’t allow growth to decrease quite so much,” he says. You can counterbalance some of the negative effects of that first winter for the weanling and make up for some deficiencies in the environment, such as providing good quality hay.
“If a foal really drops off in growth
(such as at weaning when he’s stressed
and especially if forage availability and temperature are less than optimal) with all
of these stresses happening at once, he makes up for it later. The more an animal decreases growth at this point and conserves energy (for maintenance instead of growth), when spring comes and there’s good grass again, the more the animal tries to catch up,” he says. This growth spurt is called compensatory growth and happens in all species.
The more the young animal decreased growth through the first winter, the more likely there will be a greater increase in growth the next spring. It is this type of growth spurt that has been indirectly linked with developmental problems in the growing skeleton. If you can compensate for the decrease during winter and think about it in spring by not accentuating
a growth spurt by feeding high-energy feeds
at that time, this can smooth out the peaks
and valleys of the young horse’s growth and potentially help minimize some of the risk for DOD (developmental orthopedic disease).
“This bumpy pattern of growth may or may not be detrimental. In extremes, it may play a role in skeletal abnormalities. One study from the 1940’s and 50’s looked at wild horses’ patterns of growth. The young ones grow slower in winter and speed up in spring. These are normal cycles,” says Staniar. But, fast growth in a wild horse is not as extreme as that of a domestic youngster
on lush pasture or one that’s being fed grain and other concentrates to push for faster growth in order to get ready for early training. Wild horses mature more slowly in a natural environment.
“We must be careful in making a comparison of wild horses and domestic horses in regards to what we expect from our top athletes,” he says. Subjected to completely natural conditions, such as harsh winters and intermittent nutrient levels or shortage of available feed, a horse might not be able to develop full potential as a top athlete.
“The young horse’s muscles and skeleton are all making decisions for growth based on how much and what kind of stress they are under.”
“Breeders should pay attention to
growth rates, measuring weight and skeletal development. You could do this as often as
every 2 weeks, but at minimum I’d recommend taking measurements once a month. A weight tape isn’t as accurate as a scale, but can be a good estimate if you’re just looking for changes. There are also some good equations available for weight estimations, for growing foals,” he says.
Problems can occur in foals if we try to maximize growth, and some foals - either due to genetics and/or environment - tend to grow too fast. The first step in dealing with this is awareness. If in your breeding decisions you’ve chosen a large mare and a large stallion and you expect the foal to grow rapidly, you should closely monitor that growth.
“There’s a perceived connection between rapid growth and developmental problems. The mistake some people make is to take the animal off all energy to try to halt the rapid growth. It’s more important to look at the big
Breeders should pay attention to growth rates, and a foal should be measured often.
62 SPEEDHORSE, August 2015
equine health