Muscle fibre growth in undernourished reindeer calves (Rangifer tarandus tarandus L.) during winter

To study whether moderate under-nutrition causes muscle wasting, reindeer ( Rangifer tarandus tarandus L.) calves were fed either pelleted reindeer fee d ad libitum (n = 8) or restricted amounts of lichens (n = 8). The restrict ed amount was 60% of ad libitum intake of lichens, and the feeding period w as 6 weeks preceded by a 2-week adjustment period. Biopsy samples from the middle gluteal muscle (M. gluteus medius) for the analysis of fibre composi tion and area, as well as for the activity of cathepsin B were taken before the restriction period in November and January, and after the restriction period in April. In all calves the muscle fibre composition remained unchan ged during the winter. In the lichen group, the fibre size also remained un changed, whereas in control calves the cross sectional area of type I and t ype IIA fibres increased significantly from November to April. Cathepsin B activity decreased in all calves from November to January and remained at t hat low level for the rest of the study period, which suggests an attenuate d rate of protein degradation. These results can be taken as an indication that moderate under-nutrition causes no muscle wasting in reindeer calves, and the decreased availability of nitrogen is partially compensated for by adaptive decrease in protein degradation. Interestingly the adaptive change s in protein metabolism are equally well seen in the well-fed controls as i n the undernourished lichen-fed reindeer. (C) 2001 Elsevier Science Inc. Al l rights reserved.