Performance Horses: Forage or Grain Before Strenuous Exercise?

It turns out that forage, not grain, should be fed 4-6 hours before strenuous exercise. High starch diets induced acidemia, acidification, increased urinary mineral excretion, decreased bone mineralization and increased plasma lactate. This suggests a causal link between stress fractures, developmental orthopedic diseases, fatigue, and rhabdomyolysis from the high-grain diets of performance horses and rapidly growing foals. High-starch diets caused increased fermentation and lower cecal and large colon pH than high-roughage diets. Sweet feeds caused decreased venous pH and increased respiratory rates when compared to grains with no added glucose or sucrose. In one study, mature mares fed a 60 percent grain ration had lower fecal and venous pH and higher urinary excretion of calcium and phosphorous than mares fed a 10 percent grain ration with equivalent protein and calories. A single meal of high starch sweet feed reduced venous pH within one hour while decreasing urine pH and increasing urine calcium and phosphorous within 4-6 hours. When compared to a meal of hay which resulted in an increase of venous pH and a significantly smaller increase in urine calcium and phosphorous excretion. If sodium bicarbonate was added to the ration at 140mg-300mg per kg body weight, the horse's venous pH increased which reduced overall acidemia with anaerobic or strenuous exercise, and blocked the acidemia-associated reduction in muscle glycolysis. In conclusion, the effect of diet seems to play an important role in a horse's acid-base status which could lead to better performance and health.

---------------------------------------------------------------------------------------------------------------------------Ralston St Dept Anim Sci Cool College Rutgers University NJThe effect of diet on acid-base status and mineral excretion in horses Eq Prac 16(7) 10-13.