Fat tolerance of cod
The purpose of this study was to investigate the effect of fat content in feed on the growth and cleaning of cod of different sizes. Knowledge of the nutritional needs of fish is a necessary prerequisite for the preparation of feed for them. Two-size cod (120 g and 600 g) were fed (in triplicate) for 12 weeks on feed containing 10.0%, 13.5%, 21.2%, 24.5% and 27.7% fats in dry matter. Different fat content did not affect growth (SGR), body mass index (CF), fillet utilization, liver fat content or fillet fat content. In the smaller fish, the feed index (FCR) decreased with increased fat in the feed. The feed fat did not affect the fat content of offal without liver in the smaller fish (120g) but in 600 g fish the fat in the intestines increased with increased fat content of the feed. The fat content did not affect the proportion of gutted weight of the total weight in the 600 g fish, but in the smaller fish the proportion decreased with increased fat in the feed. Liver ratio (HSI) in 600g fish was not dependent on the fat content of the feed, but there was a positive correlation between feed fat and HSI in the 120 g fish. This means that the fat tolerance of cod in terms of liver ratio depends on the size of the fish.
Detailed knowledge of the nutritional requirements of fish is essential for feed formulation. The aim of this research was to investigate the effects of different lipid content in diets for Atlantic cod of different size. Cod of two size groups (initial weight 120 grams and 600 grams) were fed, in triplicate, for 12 weeks diets containing 10.0%, 13.5%, 21.2%, 24.5% and 27.7% lipid in dry matter. Different lipid content in the diet did not affect growth (SGR), condition factor (CF), fillet yield, lipid content in liver or lipid content in fillet. In the smaller fish, FCR was reduced with increased diet lipid. The lipid content in the diet did not affect the lipid content of intestines in the 120 grams fish but in the 600 grams fish there was a positive correlation between lipid content in diet and intestines. Dietary lipid did not affect gutted weight (calculated as the percentage of round weight) in the 600 grams fish but in the 120 grams fish, the percent gutted weight decreased with lipid content of the diet. The Heposomatic index (HSI) in the 600 gram fish was not affected by the lipid content of the diet but dietary lipid content significantly affected the HSI in the smaller fish. This indicates that the lipid tolerance of Atlantic cod, with respect to the effect on HSI, is size dependent.
