抄録
The effect of maintenance (zero-energy balance) and submaintenance (negative-energy balance) and of subsequent compensatory growth (repletion) on the micro- and ultrastructure of L. dorsi muscle from young lambs was investigated. This study showed that fibre diameter and sarcomere length did not change significantly due to maintenance feeding but submainten-ance feeding caused a marked decreased in these parameters. The microscopic appearance of collagen was a dense, course fibrillar type, and occurred in thicker bundles in the muscle of under-fed lambs. However, the nature elastin was similar in all lambs.
The under-feeding also caused pronounced reduction in the amount of glycogen granules and the number of mitochomdria in muscle. The sarcoplasmic reticulum and T-system did not seem to be related to the nutritional status of the animals. The myofibrils remained normal during maintenance feeding, whereas submaintenance feeding resulted in some degen-eration of actin and myosin filaments. However, there was no difference in the sarcomere periodicity or banding pattern of the normal portions of degenerated myofibrils.
The general features and appearance of fibres, and the fine structure of myofibrils and cellular components of the muscle from the replenished lambs became identical to that of normally grown lambs at the same age. The collagen, however, was still moderately dense and the fat cells were small in the repleted lambs.
