Muscle fibre type histochemistry showing the frequency of oxidative fibres in samples across the developmental period. NADH-Tr histochemistry was used to identify oxidative fibres in sections of LD muscles from animals sampled at 80, 100, 120, 150 and 230 days of development (n = 3 at each developmental stage). (a) Examples of histochemical staining patterns in a 120 d fetal sample (left panel) and a sample taken at 230 d of development (young immature lamb) (right panel). (b) A series of random grey-scale images was collected from each section and converted to pixel grayscale intensity values. The average frequency across the images from each sample was calculated and the mean for the three animals at each developmental time was then graphed. Greater pixel intensity corresponded with increased staining and therefore higher oxidative activity. The developmental times are differentially colored: 80 d (black); 120 d (yellow); 100 d (red); 150 d (blue), and; 230 d (purple).