Blood, ensiled or frozen, as feed for salmonids

Abstract

Blood from the slaughtering of cattle was tested as a protein source in moist diets for large rainbow trout ( Salmo gairdneri Richardson) and salmon ( Salmo salar L.). The blood was used in its natural form. In the first experiment the blood was preserved by acid, and in the second experiment it was preserved by freezing or by acid. The control diet contained fish or fish offal and binder meal. In the test diets blood replaced half the amount of raw fish or fish offal which represented nearly 20% of the protein in the feed. Unlike frozen blood, blood silage did not cause pellet consistency problems. No negative effects with respect to weight increase, health, body composition or organoleptic properties of the fish were observed when blood was used in the diet or when formic acid was used as preservative instead of freezing the fresh commodity. The apparent digestibility of blood protein exceeded 97% and was not significantly affected by the various methods of preservation.