Survival and growth of first-feeding common carp larvae fed artificial diets containing soybean protein concentrate

In recent years, much progress has been made in the rearing of common carp larvae fed only with artificial diets. Such diets based on yeast and beef liver have also been used with success with larvae of several other species such as whitefish, sturgeon and grayling. A preliminary study was made in an attempt to evaluate the potential use of soybean protein concentrate (SPC) in such larval diets. Five experimental diets were formulated and compared with the control diet (C) containing yeast (Protibel, France) and beef liver as protein sources: 4 diets (K1 to K4) containing 20% yeast and 55% SPC, with 5% of either fish soluble protein concentrate (CPSP), squid powder or soy lecithin, and another diet (K5) containing 70% SPC and 10% CPSP. All experimental diets contained cod liver oil (5%), mineral and vitamin mix (5% each) and sodium alginate (3%). Diet K1 was comparable with diet K2 but contained only 2% of the vitamin mixture as against 5% in the latter. Two hundred carp larvae were grown in each of 12 different tanks at a water temperature of 24 plus or minus 1 degree C over a period of 21 days (photoperiod 16L/8D). They were fed the different diets using automatic feed dispensers over the light hours of the day. Another duplicate group was fasted. At the end of the 21-day trial, survival was best in the control group (96%) followed by those fed diet K3 containing 20% Protibel, 55% SPC and 5% soy lecithin. All other dietary treatments led to poor survival (15-45%) and to very low growth rates. Growth performance was worst with diet K5 containing SPC alone. Final body weight of the larvae fed the control diet over 21 days was 170 mg, while in the rest of the groups this was below 40 mg (diet K4). Decrease in the level of incorporation of vitamin mix led to a significant reduction in growth and survival. Soyprotein concentrate cannot be utilized in larval diets without proper supplementation with sulfur amino acids like methionine; soybean lecithin has a beneficial effect on larval survival.