Individual metabolic differences predict the spontaneous emergence of breast muscle myopathy in broiler chickens

Individual variability is a fundamental characteristic and one of the long-standing mysteries in biology. Significant differences in health are observed even among isogenic, simple organisms such as yeast or worms, maintained under homogeneous and strictly controlled laboratory conditions. The inability to predict which individuals will be fit and resilient and which will be more susceptible to frailty and disease has led to the hypothesis that a fundamental aspect of healthspan is stochastic. Here, we use isogenic broiler chickens ( Gallus gallus domesticus ) as an animal model for a breast muscle pathology known as wooden breast (WB). Intensively selected for exceptional growth rate and meat yield, broilers exhibit natural and spontaneous emergence of varying degrees of WB myopathy among individuals, making them a unique model for studying natural variability in muscle pathologies. Applying metabolic profiling and physiological measurements, we found that metabolic differences among individuals were associated with and predictive of variability in the emergence of WB myopathy. Molecularly, we identified metabolic biomarkers that predict which animals will remain healthy and which will develop severe WB. Physiologically, WB development was significantly associated with metabolic efficiency; WB birds grew faster and consumed less feed to achieve the same weight gain. Because molecular markers are often conserved across species, future studies may use broilers to further investigate the molecular phenotype and improve our understanding of individual susceptibility to muscle pathologies - not only in birds, but potentially in other vertebrates as well.