Browsing by Author "Kalmu, Niina"

Poultry meat has become popular in human diet and to secure the growing demand of poultry meat, breeders have developed broilers with fast growth and high breast muscle yield. Because of this genetic selection modern broilers are suffering from various quality defects in their breast muscles, one of which is called WB myopathy. The aim of the thesis was to study whether exercise, WB status or age have effects on ultimate pH and glycolytic potential (sum of total glucose and lactic acid content, given as lactate) in M. pectoralis major of modern broilers chickens. A total of 154 post-rigor breast muscle samples of male broilers of hybrid Ross 308 were used in this study. Broilers were divided randomly into three groups (A-C). Group A birds were not subjected to any exercise during the experiment. Group B birds lived 25 days exactly like group A but after that the drinking water dispensers was elevated to a higher level. Group C birds had their drinking water dispensers elevated to a 5 cm higher level after three days, and it was risen stepwise to 25 cm during the study. Broilers were slaughtered randomly from different groups at 20, 30 or 41 days old. Group B results were disregarded due to technical problems. Initial and ultimate pH, total glucose, free and in glycogen, and lactic acid contents for glycolytic potential, were determined from the breast muscle samples. The results showed that there were no differences between groups A and C (p > 0.05). There were differences between normal and WB cases in ultimate pH (pHu; p = 0.000), total glucose content (p = 0.000), lactate content (p = 0.007) and glycolytic potential (p = 0.000), but the pH values 5 minutes after death showed no significance (pH5; p = 0.190). There were differences in pHu, total glucose and glycolytic potential (p = 0.000), and lactate (p = 0.007), between ages 20, 30 and 41 days old birds. As the severity of WB increased in the breast muscle, the pHu increased and total glucose, lactate content and glycolytic potential decreased. The correlations showed significant relationships between WB score and all the above variables (p < 0.000). The results of the current study show that exercise does not have an effect on the levels of carbohydrates in M. pectoralis major of modern broiler chickens, but WB status and increasing slaughter age result a decrease in glycolytic potential and increase in ultimate pH.