Age-related changes and location of type I, III, IV, V and VI collagens during development of four foetal skeletal muscles of double-muscled and normal bovine animals.

The aim of this work was to study the variability in the quantities of hydroxyproline, of type I and III collagens and in the location of types, I, III, IV, V, VI in four muscles of normal and double-muscled (DM) cattle. Samples were collected from foetuses at different ages post-conception. Both in the two genetic types and in muscles, from 110 days, types I, III, V, VI were located in perymisium and types I, IV, V, VI in endomysium. The amounts of hydroxyproline and of type I collagen increased from 150 to 180 or 230 days then decreased up to 260 days, with a trend to lower quantities in muscles of DM animals. Depending on the muscle and of the genetic type, amounts of type III, or changed as those of type I, or remained stable. Whatever the genetic type, at the end of gestation, proportions of type I and III in the total collagen are not identical in the four muscles, differences between muscles being particularly marked for type III, CT and MA muscles being the richer in this type. In addition, these two muscles contained less type III in DM animals than in normal ones.