THE EFFECT OF NUTRITION AND EXERCISE ON CARCASS PARAMETERS AND THE LEVEL OF GLYCOGEN IN SKELETAL-MUSCLE OF MERINO SHEEP

This study investigated the effects in sheep of feed intake and exerci se training on (i) the level of glycogen in muscle, and (ii) carcass q uality traits including growth rate, carcass weight, fat score, and th e ultimate pH of muscle. Merino wethers, 12-months-old and starting bo dy weight 38 kg, were individually penned and housed indoors. The effe cts of nutrition and exercise were tested for 2 levels of activity (se dentary v. exercised) and 4 levels of feed intake (1, 1.3, 1.5, 2.2xma intenance) with 8 sheep per group housed individually. Exercise traini ng was for 1 h at 8-9 km/h (approx. 55-65 VO(2)max), 3 times per week from week 4 to 9 of the experiment. The diet was 20% cereal straw. 26% lupin grain, 53% barley grain, mineral and vitamin premix, and virgin iamycin. Animals were slaughtered at an abattoir in week 10. Regular e xercise reduced growth rate, carcass weight, and fat score, but did no t affect intake. At the highest level of intake, carcass weight was re duced by 0.53 kg and fat depth over the 12th rib (GR fat depth) by 6.3 mm, suggesting that muscle yield was increased. At all sampling times , the level of glycogen in the m. semimembranosis (SM) and m. semitend inosis (ST) increased linearly with increasing feed intake. Regular ex ercise caused increased glycogen level in SM samples immediately post- slaughter and in the SM, ST, and m. longissimus dorsi (LD) 48 h post-s laughter. The ultimate pH of muscle was reduced as the level of feed i ntake increased for all muscle groups. Exercise caused a reduction in the ultimate pH of the ST with no change for the SM and LD. The result s indicate that glycogen levels in muscle are highly responsive to nut rition and regular exercise. In addition, exercise caused a reduction in subcutaneous fat with no change in feed intake.