Abstract
The digestibility of beef tallow and various hydrogenated fish oils with different melting points (mp.) was determined with carp and rainbow trout. The experiment was also conducted to see the effects of fish size and water temperature on the digestibility of these lipids.
The digestibility of hydrogenated fish oils was found to be affected by their mp. and increased as mp. decreased. Whereas the digestibility of dietary protein was as high as 98% without regard to that of lipids. The hydrogenated oils of mp. 53°C was significantly low in digestibility in both carp and rainbow trout, especially in the fish weighting less than 10g. On the other hand, the beef tallow and the hydrogenated fish oil of mp. 38°C were effectively utilized by both the fish, more than 70% in digestibility regardless of the fish size and water temperature, indicating that these lipids are available as a dietary energy source without any adverse effects on fish growth, feed conversion, or survival, when they are used with some marine lipids to provide the necessary level of essential fatty acids.
