Influence of selection for breast muscle mass on myosin isoform composition and metabolism of deep pectoralis muscles of male and female turkeys

Abstract

Advances in genetic selection and nutrition have resulted in rapid growth rates and increased muscle mass, predisposing turkeys to muscle disorders such as deep pectoral myopathies and increasing the incidence of pale, soft, and exudative muscle. The objective of this study was to determine if selection for breast muscle mass created an increase in anaerobic capacity of the deep pectoralis muscle. A total of 67, 18-wk-old, male and female turkeys from two male (tom) lines and one female (hen) line were used. Each bird was anesthetized and one deep pectoralis muscle was electrically stimulated via the pectoral nerve. Muscle pH was recorded every 30 s for 4 min of stimulation and every 1 min for a 10-min recovery period. Non-stimulated muscles, contralateral to the stimulated side, were assayed for lactate dehydrogenase (LDH) and glyceraldehyde phosphate dehydrogenase (GAPDH). Myosin isoforms were resolved with SDS-PAGE. Line or gender had no effect on rate of pH decline during or after stimulation. Declines in pH during stimulation were greater than during the recovery period (0.06 vs. 0.02 U/min). The lightweight male line (LM) had the greatest breast muscle mass as a percentage of body weight (P < 0.05) and the greatest LDH [293 mmol nicotinamide adenine dinucleotide (NADH) min(-1)microg(-1); P < 0.0001] and GAPDH (0.4452 mmol NADH min(-1)microg(-1); P < 0.05) activities. Hens had greater percentages breast weight than males (P < 0.05) and a tendency for increased enzyme activities. The LM line had the largest ratio (2.33:1) (P < 0.05) of adult-to-neonatal myosin. Genetic selection for breast muscle mass resulted in an increased ratio of adult-to-neonatal myosin and increased anaerobic capacity. This effect on myosin isoform composition and anaerobic capacity supports handling modifications that are line specific to minimize meat quality defects.