With the arrival of cold weather, many horse owners consider how to increase the caloric intake of some of their horses by adding additional fat calories, especially those horses that tend to hard keepers or horses that score 4 or below on the body condition scale.
Keeping horses healthy
Fat supplies more than twice the calories of carbohydrates on a weight basis and this is particularly beneficial in fit horses that limit their voluntary food intake.
In some cases, fat is added to the diet because it is energy dense and low volume. Fat supplies more than twice the calories of carbohydrates on a weight basis and this is particularly beneficial in fit horses that limit their voluntary food intake.
Fats are also used as energy by aerobic metabolism especially during prolonged endurance exercises. Horses that are aerobically fit use fats to a greater extent than horses that are not so fit. Fat helps preserve glycogen stores and allows the horse to maintain a higher blood glucose level during prolonged exercise.
Fat is a readily digested feed additive which delivers almost two and a half times as much energy and calories as the same quantity of grain.
In a recent feeding trial, the addition of fat (soybean oil) to a grain meal was seen to affect glucose and insulin.
An experiment carried out at Kentucky Equine Research (KER) was designed to evaluate whether adding fat to a grain meal would affect glucose and insulin response to feeding when the level of grain intake remained the same.
When fat is substituted for carbohydrate isocalorically (calorie for calorie) in a horse’s ration, blood glucose and insulin responses to feeding are reduced. It was unclear, however, whether this response was simply due to reduced glucose in the diet or if fat affects glycemic response in some other manner.
Nine Thoroughbred horses were used in this two-period switchback design experiment. Five of the horses were in training and were physically fit, and four were untrained.
Blood samples were taken from each horse by jugular catheter before feeding and at 1, 2, 3, 4, 6, 8, 10, and 12 hours post feeding. Water was available to the horses at all times. The same procedure was followed two weeks later with the soybean oil added to the grain of the four horses that served as controls during the first period.
These blood samples were collected and analyzed for lactate, glucose, and insulin at the conclusion of the study.
Blood glucose was significantly lower one hour after feeding when soybean oil was added to the diet. Glucose remained lower for 3 hours post feeding. After 6 and 10 hours, blood glucose was higher in the fat-supplemented group. Insulin was lower in the fat-supplemented group 1 hour after feeding. After 8 and 10 hours, insulin was higher in the fat-supplemented group.
Plasma L-lactate tended to be higher in the control group 4 hours after feeding and higher in the fat-supplemented group 6 hours after feeding.
These data suggest that the addition of fat (soybean oil) to a grain meal will affect glucose and insulin response to feeding. These effects are independent of the amount of carbohydrate in the diet and may be due to differences in the rate of gastric emptying when fat is included in the diet.
As a general conclusion, when energy in the form of fat is used to replace starches and sugars, blood glucose levels remain low. This reduces the risk of metabolic syndromes such as Cushing's disease from developing.
This article is based on information in a paper titled “Responses of Blood Glucose, Lactate and Insulin in Horses Fed Equal Amounts of Grain With or Without Added Soybean Meal” by J. Pagan, T. Rotmensen, and S. Jackson.