Dietary influences on product quality in African catfish (Clarias gariepinus)

In this trial a full-sib family of Clarias gariepinus was raised under standard conditions in a warmwater recirculation system. The fish were divided into two experimental groups of 1200 individuals each and were raised in separate tanks. The groups were fed two experimental diets differing in crude protein (group I 40% and group II 52% DM) and crude fat (group I 8% and group II 13% DM). Gross energy was 21.3 and 22.1 MJ/kg. Slaughtering of 100 fish per group (50 males, 50 females) took place after two experimental periods. Besides the significant effect of the diets on body weight and size, a higher degree of corpulence was observed in group II. Tissue and organ percentages were not influenced, except a higher intestinal fat deposition in intensively fed fish. This group also showed a higher carcass weight. More expressed differences between both feeding alternatives were observed in physical and chemical flesh quality criteria. In group I texture of flesh was firm and water-binding-capacity was significantly increased in group II. The appearance of the filet was affected by the diet. Intensively fed catfish showed a tendency to a lighter and more yellowish colour. The chemical composition of the flesh indicated a significant increase of dry matter caused by higher protein and fat contents in this group. A strong influence of sex and fattening age on inner and outer product quality was evident. High fat and protein content of the diet has a certain influence on product quality in African catfish. It can be concluded that there is a clear effect of diet on quantitative criteria with a tendency to higher slaughtering yields in intensively fed catfish.