FEED QUALITY RESTRICTION AND COMPENSATORY GROWTH IN GROWING SHEEP - FEED-INTAKE, DIGESTION, NITROGEN-BALANCE AND MODELING CHANGES IN FEED-EFFICIENCY

The effects of feed quality restriction on intake, digestion, nitrogen balance, feed conversion efficiency and performance were examined. A total of 56 crossbred Swifter (Flemish female x Texel male) male lambs born in March 1993 and weaned at approximate to 2-months old were fed grass straw (51 g crude protein (CP) per kg dry matter (DM)) ad libit um and 35 g kg(-0.75) d(-1) mixed concentrates (173 g CP kg(-1) DM). A t an age of approximately 3 months, animals were randomly divided into a restricted (R) and a control (C) group. Group R was restricted in f eed quality by withholding concentrates from 3-6 months of age. During restriction, the R animals lost weight and showed a slightly negative nitrogen (N) balance. Grass straw intake of the R animals gradually i ncreased to a level significantly higher (P < 0.001) than of the C ani mals. The R animals showed a significantly (P < 0.001) higher rumen re tention time (RRT). The shape of the growth curve changed by feed qual ity restriction. A model was developed to measure feed efficiency from the relation between cumulative feed intake and body weight. The feed efficiency was negative for R animals during restriction. After reali mentation, R animals were more efficient in converting feed to body we ight compared to C animals. The delay in growth after restriction was compensated during realimentation though with lower total feed consump tion. (C) 1997 Elsevier Science B.V.