A COMPARISON OF GRAIN, VEGETABLE OIL AND

J.D. Pagan1, P. Harris2, S.E. Duren1 and S.G. Jackson1

1Kentucky Equine Research, Inc., Versailles, KY 40383

2Waltham Centre for Pet Nutrition, Waltham-on-the-Wolds, Leic., UK

Introduction

A number of studies have evaluated the effect of adding fat to a performance horse’s diet. Most have replaced a portion of the grain in the ration with fat, so that total carbohydrate intake was reduced. Little research has been conducted to evaluate the effect of substituting other energy sources for starch.

Therefore, this experiment was designed to compare a traditional high grain diet with diets which provide 15% of the total caloric intake from either vegetable oil or a highly fermentable fiber source

(beet pulp).

Materials and Methods

Six three year old Thoroughbreds (4 geldings, 2 fillies) were fed one of three diets in a

replicated 3X3 Latin Square design where each period lasted 5 weeks. Diet 1 (CONTROL) consisted of 3.62 kg of sweet feed (47% oats, 42% corn and 11% molasses) and .9 kg of a balancer pellet (table 1). Diet 2 (FAT) contained 15% of the daily DE as soybean oil and Diet 3 (FIBER) contained 15% of the daily DE as beet pulp. The oil and beet pulp replaced sweet feed so that the diets remained isocaloric on a digestible energy basis. The horses were also fed 5.43kg of an alfalfa/whole corn plant cube (Alfamaize) daily.

 

The horses were exercised 3 times per week on a high speed treadmill during the first 4

weeks of each period. During the last week of each period, the horses performed a standardized exercise test (SET) on the treadmill. The SET consisted of a warm-up (WU), which included a 2 minute walk and an 800 meter trot (~4 m/s), an 800 meter gallop at 8.5 m/s (20 mph) and a 2400 meter gallop at 11 m/s (26 mph) followed by a warm down (wd) of 800 meters at the trot (~4 m/s) and a 2 minute walk. Each horse performed the test 3 hours after eating only the grain portion of their morning meal. Heart rates were recorded during the last 15 sec. of each 800 meter interval. Blood samples were drawn from an indwelling jugular catheter before eating, at 30 minute intervals

up to the SET, after the warm-up, at the end of every 800 meters at the gallop, after the warm down and at 15 and 30 minutes post exercise. The collected plasma was analysed for lactate, glucose, cortisol, insulin, triglycerides and glycerol. The heart-rate velocity relationship was determined by linear regression of heart rate during the last 15 sec. of each 800 meter interval on speed and expressed as V200. The lactate-velocity relationship was determined by regressing the logarithm of lactate against speed and expressed as VLA4.

Results and Discussion

Blood glucose was significantly lower (p<.05) in the FAT horses during the three hours

post feeding as compared to either the CONTROL or FIBER fed horses (figure). Insulin was also significantly lower (p<.05) in the FAT horses both post feeding and throughout exercise. Cortisol was significantly lower (p<.05) in the FAT horses as compared to the CONTROL fed horses during exercise. Following the SET, the FAT fed horses drank

significantly more (p<.10) water (7.0 liters) than either the CONTROL (4.8 liters) or the

FIBER (4.7 liters) horses. Substituting 15 % of DE as vegetable oil had a greater effect