Symmorphosis and livestock bioenergetics: production animal muscle has low mitochondrial volume fractions

A comparative analysis of skeletal muscle structure reveals that production species (nine species, representing three mammalian families and an avian family) have mitochondrial volume fractions (MVF) 37% lower than the non-production species at equivalent size (17 species, with representatives from 10 mammalian families) (Fig. 1; F(1,25) = 4.79; p = 0.039). As MVF provides evidence of oxidative capacity, this comparative analysis indicates that production animals share an exceptionally low oxidative capacity muscle phenotype. A possible bioenergetic reason for this observation, relating to a reduction in the cost of maintaining trans-membrane ion gradients is briefly discussed. This discussion is framed within a biological economic design theory called symmorphosis and makes predictions about avenues for improvements in livestock bioenergetics.