INFLUENCE OF TREADMILL EXERCISE ON PITUITARY-ADRENAL SECRETIONS OTHER BLOOD-CONSTITUENTS, AND MEAT QUALITY OF SHEEP

Wether lambs were used to evaluate the influence of treadmill exercise (TME) on physiological responses and meat quality. Lambs were exercised at either 5.6, 7.2, or 8.8 km/h on a 9 degrees incline for 10 min, followed by a 10-min walk at 4.0 km/h and 0 degrees incline, or were unexercised controls (C; n = 3/treatment). Heart rates were determined at -15, 1, 3, 6, 10, and 15 min relative to the onset of exercise. Blood was collected at 2.5-min intervals during and after exercise for determination of plasma concentrations of ACTH, cortisol, and lactate. In addition, blood collected during exercise was evaluated for hematocrit and for concentrations of glucose, hemoglobin, and total protein. Exercised lambs had greater (P < .01) heart rates than C lambs during and after exercise. Blood from TME lambs also had greater (P < .001) hematocrit percentages, total protein, and hemoglobin concentrations. Areas under the ACTH and cortisol response curves were greater(P < .001) for TME than for C lambs. Areas under glucose response curves were greater for all TME treatments (P < .001) than for C and greater(P < .001) for lambs exercised at 8.8 km/h than for lambs exercised at 5.6 km/h. Areas beneath lactate response curves were greater (P < .001) for lambs exercised at 8.8 km/h than for lambs exercised at 7.2 km/h and C lambs. Carcasses from lambs exercised at 5.6 km/h had lesser(P < .05) longissimus muscle (LM) glycogen concentrations at slaughter than carcasses from lambs exercised at either 7.2 or 8.8 km/h and C lambs. At 48 h postmortem, LM pH and color were unaffected (P > .05) by TME. Treadmill exercise caused dramatic changes in blood constituents but had minimal influences on meat quality.