Effects of protein or energy restriction with subsequent realimentation on performance parameters of carp ( Cyprinus carpio L.)

Abstract

The influence of a limited crude protein or energy supply followed by an adequate supply was investigated and compared to continuous feeding of carp over a live weight range of 150–440 g for various performance parameters. Throughout the trial the control group (treatment C) was given a feed containing 18.8 kJ gross energy/g fresh matter (FM) and 38.8% crude protein in the FM at a level of 2% of the live weight. During the restriction phase (up to 250 g live weight) either the crude protein supply was reduced by about 30% with constant energy supply (treatment P), or the gross energy supply was reduced by about 37% with constant crude protein supply (treatment E). In the realimentation phase all carp were fed as the control group. In the phase of the protein restriction and during realimentation this group (P) digested the feed less well than the carp of the control group. Digestibility was somewhat improved as a result of the energy restriction. The restricted protein or energy supplies clearly slowed the growth (duration of the restriction phase 49 (P) and 47 days (E) in comparison to 35 days (C)), but only in treatment P could an increased feed expenditure per g gain be observed. In the realimentation phase the carp of treatments P (42 days) and E (41 days) showed similar weight gains to the control carp (42 days). No compensatory growth effect occurred. Treatment E, however, tended to improve feed expenditure. As compared to the control group, the carp under protein restriction had carcasses richer in dry matter, fat and energy. After energy restriction the carcasses were poorer in dry matter, fat and energy, but richer in protein than the control carp. In the course of realimentation, the differences, especially between treatments P and C, diminished, but the carcasses of treatment P carp were still fattiest. The carcasses of treatment E fish contained least fat, even after realimentation.