Like any neonate, a newborn foal depends on its mother's milk as its primary source of nutrition for the first few months
of life. According to the National Research Council (NRC) Nutrient Requirements of Horses 2007, foals begin to suckle within
one to two hours of birth.
Thoroughbred foals nurse about 10 times an hour for the first day for about 60 to 80 seconds at a time. For the first month,
a Thoroughbred foal suckles about 45 minutes daily, with milk consumption at about 15 kg/day. At first, feral neonates have
been noted to nurse 6 to 8 percent of the day, decreasing to about 2 percent by 8 weeks of age.1
"The timetable of foals getting up, standing and suckling is important, not just in regard to receiving colostrum and its
immunoglobulin content, but also because the foals only have a little bit of liver glycogen in their system," says Mary Rose
Paradis, DVM, MS, DACVIM, of Tufts University Cummings School of Veterinary Medicine. "Usually that amount starts to be used
up and is gone within a couple of hours or so. So foals need to have that colostrum to help bring their blood glucose back
up. The glycogen begins to fall within two hours, as does their blood glucose, which is then a trigger for them to stand and
nurse to get it.
PHOTO COURTESY OF MARY ROSE PARADIS, DVM, MS, DACVIM, TUFTS UNIVERSITY CUMMINGS SCHOOL OF VETERINARY MEDICINE.
"A lot of the sick foals we see that are less than 24 hours old are very hypoglycemic because they never got that source of
colostrum, and, therefore, they are depleted in blood glucose," Paradis continues. "Colostrum is important because it is different
in composition than regular milk, so if foals get a colostrum feed, then they are probably good for about 15 hours or so,
even if they didn't get any additional milk. The colostrum is appreciably higher in energy (also protein and vitamins A and
E)—so its benefit lasts longer—and in crucial preformed antibodies needed within eight to 12 hours. The frequency of a normal
foal nursing is about seven times an hour. When that occurs, obviously they have a high need for food, and at each feeding
they are probably going to get about 80 ml of milk, which is almost half a liter per hour. You are then looking at a normal
50-kg foal consuming about 12 to 15 liters of milk per day."
The foal's changing GI anatomy
A newborn foal's gastrointestinal tract is quite different from that of an adult horse. In a foal's first month of life, the
small intestine is the site of most growth, growing in both length and diameter, which increases the surface area of the villous
surface for the digestion and absorption of the milk meals. The large colon plays a minor role. During this first part of
a foal's life, the small intestine is the absorptive surface for its liquid diet.
"They really don't have enzymes to digest any of the other foods yet, so lactase is the prominent enzyme," Paradis says. "At
2 to 3 months of age, they get maltase, which helps digest some of the other things they might consume at that age, such as
creep feed or small amounts of forage. At 4 months old, maltase takes over, and the lactase decreases."
Although owners want to have some food out so that the foals can recognize what hay, grain and other feedstuffs are, foals
primarily learn feeding behavior from their dam, according to Paradis. At first though, they are not going to get much of
any other nutrition except from milk, so it's important that they have a good source of milk.
During the second month of life, a foal begins to develop the cecum and the large colon as organs of digestion. However, nutritionally,
the foal still depends on mare's milk as the primary source of nutrition. Over the next three to five months, the cecum and
large intestine enlarge and begin to populate with microorganisms that assist in breaking down the structural elements of