Dietary Protein Restriction and Fat Supplementation Diminish the Acidogenic Effect of Exercise During Repeated Sprints in Horses

A restricted protein diet supplemented with amino acids and fat may reduce the acidogenic effects of exercise. Twelve Arabian horses were assigned to a 2 × 2 factorial experiment: two fat levels: 0 or 10 g/100 g added corn oil and two crude protein levels: 7.5 g/100 g (supplemented with 0.5% L-lysine and 0.3% L-threonine) or 14.5 g/100 g. The experiment began with a 4-wk diet accommodation period followed by a standard exercise test consisting of six 1-minute sprints at 7 m/s. Horses were interval trained for 11 wk followed by another exercise test with sprints at 10 m/s. Blood samples were taken at rest and during the exercise tests. Plasma was analyzed for PCO2, PO2, Na+, K+, Cl−, lactate, pH and total protein. Bicarbonate, strong ion difference and total weak acids were calculated. Data were analyzed using repeated-measures analysis of variance. Venous pH was higher in the low protein group during the first test (P = 0.0056) and strong ion difference became higher (P = 0.022) during sprints in the low protein group. During the second test, venous pH and bicarbonate were higher for the low protein high fat group (P = 0.022 and P = 0.043, respectively) and strong ion difference became higher (P = 0.038) at the end of exercise in the low protein groups. These results show that restriction of dietary protein diminishes the acidogenic effect of exercise, especially in combination with fat adaptation. J. Nutr. 131: 1959–1964, 2001.