Availability of protein and energy from three protein sources in hybrid sturgeon Acipenser guldenstadti × A. bester

The apparent digestibility coefficient (ADC) of three diet ingredients serving as protein sources for adult sturgeon Acipenser guldenstadti × A. bester was studied using an inert marker in the feed and collecting the faeces by stripping. Each experimental diet contained a different protein source, fishmeal, soybean meal and poultry meal, making up 50% of the total, the other 50% being reference diet (28% fishmeal, 9% poultry meal, 24% soybean meal, 26% wheat flour, 8% poultry oil plus 0.5% vitamins, egg yolk, guar and chromic oxide). The digestibility of protein from fishmeal was 81.0%, from soybean meal 81.9% and from poultry meal 64.6%. Energy digestibility tests gave the following results: fishmeal 13.0 kJ g^?1; soybean meal 12.1 kJ g^?1; and poultry meal 10.2 kJ g^?1. The differences in the ADC of various protein and carbohydrate sources are discussed.