Comparative observations on the growth changes of the histochemical property and collagen architecture of the Musculus pectoralis from Silky, layer‐type and meat‐type cockerels

Abstract

Growth‐related changes in the histochemical properties and collagen architecture of the Musculus pectoralis were compared among Silky, layer‐type and meat‐type cockerels. Histochemical and immunohistochemical methods were used and collagen architecture was studied using scanning electron microscopy. The total amount of collagen present was also measured. The diameter of type IIB myofibers was similar or rather larger in the layer‐type birds compared with the meat‐type. The collagen content was generally low for 5–10 weeks across the breeds and then increased in the other breeds except for Silky. In the perimysium, the collagen bundles gradually increased in size and the density of the fibrils also increased during growth. At 30 weeks of age, the layer‐type birds showed compact collagen bundles while the meat‐type had loose bundles. The endomysial collagen network appeared relatively denser in the meat‐type chicks compared to the others at week 1. At 30 weeks of age, compact and felt‐like structure of endomysium was shown by Silky and layer‐type chickens, while the meat‐type showed a relatively loose arrangement of tissue in the endomysial collagen. From these results, it appears that the meat‐type chicken can produce a large M. pectoralis with many, relatively thinner myofibers and a relatively undeveloped form of intramuscular collagen structure.

Collagen content and architecture of the pectoralis muscle in male chicks and broilers reared under various nutritional conditions

“…This growth‐related change of endomysial thickness has already been reported in chickens (Nakamura et al. 2004; Oshima et al. 2007a,b),wild boars and domestic pigs (Fang et al.…”

“…Because the collagen concentration remains within a relatively narrow range throughout the different growth stages (Nakamura et al. 2004; Oshima et al. 2007a,b), inconsistent results may be obtained depending on the experimental conditions.…”

“…2006). Moreover, SEM photographs of the perimysium of 30‐week‐old cockerels reared with a layer breeding system do not show the plate type collagen fibers (Oshima et al. 2007a).…”

Comparative observations of the growth changes of the histochemical properties and collagen architecture of the iliotibialis lateralis muscle from Silky, layer and meat type cockerels

“…In the pectoralis muscle the collagen content is low between 5 and 10 weeks of age, a similar age to a general broiler, and then by 15 weeks of age increases to about twice the original value in meat birds and layers (Oshima et al . 2006).…”

“…In the present study, in the iliotibialis lateralis muscle the same tendency was recognized in the layers but not in the meat birds, indicating that the result depended on the muscle type. Silky birds, with their small body size, showed the lowest collagen content in both the pectoralis and iliotibialis muscles (Oshima et al . 2006).…”