Effect of protein on the post-ingestive response of tilapia fed encapsulated diets

Abstract

Two experiments were carried out with Nile tilapia (Oreochromis niloticus) to assess whether protein concentration influences post-ingestive signaling and the ability of fish to modulate protein intake from a practical diet. The animals were fed three types of encapsulated diet: control, cellulose-based diet (CD) = 0% protein; diet with 25% crude protein (D25); and diet with 42% crude protein (D42). In the first experiment, 20 fish were divided into two groups, one being fed CD and D25 and the other fed CD and D42. In the second experiment, 15 tilapia were fed D25 and D42. In the first experiment, the two groups of tilapia consumed more capsules containing D25 (62.83%) and D42 (55.54%), and the animals that received D25 noticed the difference between the capsules more quickly (7 days of the experiment) than did those that received D42 (11 days). In the second experiment, there was a preference for capsules containing D25, compared to D42, which was demonstrated after 23 days of the experiment. The animals adjusted both the amount of crude protein ingested daily (31.86%) and the rate of daily feed consumption to biomass (1.36%). Tilapia can select the diet that best meets their nutritional needs, adjusting the protein ingested and feed consumed.