Lipoprotein profiles of the horse in response to increased dietary fat and exercise.

Abstract

Three experiments were conducted to evaluate the effects of a fat-supplemented diet on the horse. Experiment one examined the effect of a diet which contained 20% digestible energy as corn oil fed to four horses in comparison with a control group. Plasma lipoproteins, muscle lipoprotein lipase, total serum lipids, and ultrasound-estimated body fat were monitored for 10 weeks. The plasma lipoproteins fractionated into VLDL, LDL, HDL and albumin, and each was assayed for protein, cholesterol and triglyceride content. Results indicated that the fat-fed horses increased in LDL and HDL protein, VLDL triglyceride, and LDL and HDL cholesterol content. There was a slight increase in total serum lipids while body fat was unchanged. In experiment two, two horses were fed the same fat diet and two horses served as controls. Total serum lipids and plasma lipoproteins were analyzed from samples obtained during a post-prandial sampling period at 2, 4, and 6 weeks of the trial. Results indicated an adaptation by the fat-fed horses to the added dietary fat through an increase in lipoprotein protein content, suggesting larger quantities of the lipoprotein fractions. LDL and HDL cholesterol levels also increased. Finally, VLDL triglyceride levels increased in the fat-supplemented horses reflecting the increased absorption and availability for utilization of the added dietary fat. Experiment three examined the effect of a fat-supplemented diet on exercising horses. All seven horses were fed the high fat diet, and four of them were exercised. A standard exercise test was administered at the start and end of the trial to assess the conditioning program. Total serum lipids, plasma lipoproteins and percent body fat were monitored at weeks 3 and 6 of the trial. Blood samples were collected as in experiment two. The exercised horses exhibited lower VLDL and LDL triglyceride levels as well as lower LDL cholesterol levels. These data suggest that exercise increased the utilization of dietary fat for exercise in the horse, and could subsequently be used as a high-energy feed source in these animals.