Myofibre composition and total collagen content in M-iliotibialis lateralis and M-pectoralis of Silkie and White Leghorn chickens

1. Using adult Silkie and White Leghorn (WL) chickens, fibre composition an d total collagen content were compared between M. iliotibialis lateralis (I TL) and M. pectoralis (PT). 2. Fibres were divided into type IIR and IIW showing strong and weak reduce d nicotinamide adenine dinucleotide dehydrogenase activities, respectively. 3. Fibre composition differed markedly between ITL and PT muscle. ITL muscl e was composed of both types IIR and IIW fibre but PT muscle of only type I IW. Breed difference on composition was noted only in ITL muscle of cocks ( type IIR; Silkie 53.8% and WL 37.0%). 4. Total collagen content was greater in ITL muscles and in cocks in both m uscles. However, a breed difference was observed only in the PT muscle of h ens. 5. In conclusion, the total collagen content was affected by muscle locatio n within the body and by sex rather than by fibre composition.