Digestibility measurements in juvenile tench [Tinca tinca (L.)] by using a continuous filtration device for fish faeces

Effective pond production of tench [Tinca tinca (L.)] requires the use of formulated diets. However, insufficient information is available regarding the nutrition of this species. Therefore, for the first time, the digestibility of macronutrients by tench was investigated using a sieving method of faeces collection and chromic oxide. A pelleted experimental diet rich in untreated wheat starch revealed the following mean apparent digestibility coefficients (ADCs):dry matter 77.2%, crude protein 89.4%, crude fat 94.3%,ash 30.5%, nitrogen-free extracts 78.2%, organic matter 83.3% and energy 85.1%. Generally, these ADCs indicate that the ability of tench to digest the macronutrients from pelleted feed correlates with reports of other fish species.However, the tench is more able to digest untreated wheat starch than are carnivorous and coldwater fish species. Compared with carp (Cyprinus carpio L.), the digestibility of untreated wheat starch is less in tench. The faeces sieving method as described in this paper is a useful procedure for further digestibility trials with tench. However, compared with the approach presented here, several adaptations are recommended, e.g. long adaptation times to the rearing facility, high stocking densities, usage of more waterproof food pellets and the addition of formalin to the collection pans.