The third international symposium on tilapia in aquaculture

The adaptation of fish to a new feed was monitored for the first week of experiments by measuring variations in the apparent digestibility coefficient (ADC) of dry matter, nitrogen and organic matter. Three series of experiments were conducted on nine different feeds and one reference feed. Each feed was distributed to two batches of animals. Each batch comprised 15 fish (87 more or less 4 g) for the first experiment, and 20 fish (177 more or less 3 g) for the second and third experiments. Feces were collected every 12 hours (0800 and 1700) before each distribution of feed. The influence of the day/night cycle on digestibility was measured by comparing feces excreted by day with those excreted by night. ADC values obtained during the first day of distribution were significantly lower than those obtained over the following days. There was no difference between day and night in the ADCs of nitrogen and organic matter, except for the first meal. However, a slight difference between day and night in the ADC of dry matter does persist beyond the second day. To determine the ADC of a feed, the first collection of feces must occur at least 24 hours after the first distribution of feed. If fish are fed several times per day, it is best to use the aggregate of feces excreted in each 24-hour period to estimate a practical value for the different ADCs. The ADCs of dry matter, proteins (nitrogen) and organic matter were determined for several by-products available in Côte d'Ivoire : fish meal, maize meal, cassava meal, copra cake, soy cake and cotton cake. (Résumé d'auteur