Harold McKenzie III, DVM, MS, Dipl. ACVIM, assistant professor in equine medicine at the Marion duPont Scott Equine Medical Center in Leesburg, Va., discussed the challenge of providing nutritional support to sick neonatal foals in his presentation at the 2007 American Association of Equine Practitioners Convention, held Dec. 1-5 in Orlando, Fla. Many factors need to be considered–a foal’s energy requirements, his ability to digest and metabolize nutrients, the changing quality of the mare’s milk, and the ability to monitor the sick foal. McKenzie notes that some disease processes might have begun before birth. To implement a useful nutritional strategy, McKenzie believes it is helpful to first understand nutrient demands of a healthy foal.

A foal’s nutritional plan depends on his stage of growth and energy metabolism. It is possible for hypoglycemia (low blood sugar) to occur even in a healthy neonatal foal due to limited residual energy supplies as the neonate transitions from the womb and maternal energy sources to ingestion of energy from milk. With that in mind, a sick foal can experience profound hypoglycemia within even a few hours of limited or absent energy intake.

A healthy, growing foal must maintain growth at the rate of 2½% of body weight each day, and he also needs calories to support basal metabolic rate. As a foal’s body weight increases, his total calorie requirements increase, and the pancreas must secrete sufficient insulin to enable utilization of ample carbohydrates obtained from mare’s milk. Studies have shown that mares fed a diet high in soluble carbohydrates in late gestation might contribute to a decrease in insulin sensitivity in 5½-month-old foals, and this is undesirable because it might potentially create hormonal imbalances later in life. McKenzie explains that there might be some "prenatal programming" effect that could play a role in development of adult metabolic disease.

A premature foal has additional issues–he might not have experienced normal hormonal maturation signals and, thus, could be impaired in metabolic regulation tasks, leading to hypoglycemia, weakness, depression, and an inability to stand. Insulin resistance might render a premature foal unable to utilize carbohydrates that are administered by stomach tube or intravenously, so he might become hyperglycemic (high blood sugar), particularly if septic. Such an individual might need lipid-based supplementation for calories. Because the critically ill neonate can experience some insulin resistance, he could require administration of insulin coupled with hourly monitoring of blood glucose