Feed quality restriction and compensatory growth in growing sheep: development of body organs

The effects of feed quality restriction and the consequent compensatory growth on body organ development was measured in 56 crossbred Swifter (Texel male x Flemish female) male lambs born in March 1993 and weaned at approximate to 2 months of age. The ration was gradually changed to an experimental diet of grass straw (51 g crude protein (CP) per kg dry matter (DM)) ad libitum and 35 g kg(-0.75) d(-1) of mixed concentrate (173 g CP per kg DM). At 3 months of age, animals were randomly assigned to a restricted (R) or a control (C) group. Group R was subjected to feed quality restriction by withholding concentrates from 3-6 months of age. A serial slaughtering procedure was used to determine changes in body organ weights. At the beginning of the experiment eight lambs, thereafter every 3 weeks four lambs (two per group), and finally eight lambs (four per group) were slaughtered. Growth was modelled using a linear function. Estimated parameters clearly indicated reduced growth during feed quality restriction and compensation during realimentation. The carcass showed an earlier effect of restriction and realimentation compared to body weight (BW). Non-carcass components showed a delay in growth after restriction but had a similar trend to BW after realimentation. At the end of the experiment, the weight of the small intestine was higher in R group (P < 0.05). No differences (P > 0.05) were observed for other organs between groups. In general, early maturing parts (head, feet and visceral organs) have high priority for use of the available nutrients in the blood stream and are affected less than the late maturing parts by feed quality restriction. After realimentation, the responses are mainly related to their reactions during restriction, i.e., the organs which are most affected and have the greatest reduction, respond quicker than those which are less affected. (C) 1998 Elsevier Science B.V. All rights reserved.