Apparent digestibility of proteinaceous feed ingredients from animal and plant origin for two tropical species snubnose pompano Trachinotus blochii and mangrove red snapper Lutjanus argentimaculatus

Apparent digestibility coefficients (ADC) of protein and energy in a selection of ingredients of animal origin and plant origin were determined for snubnose pompano (Trachinotus blochii) and mangrove red snapper (Lutjanus argentimaculatus). Apparent digestibility coefficients (ADCs) were determined using a reference diet with yttrium oxide as an inert marker and test diets that contained 70 % of basal mash and 30 % of the feed ingredient being evaluated. Snubnose pompano and mangrove red snapper with an initial average body weight of 733.1 ± 92.3 g and 386.7 ± 37.7 g respectively, were fed with the diets for a period of 7 days before collecting faecal samples. The fish were sedated, and faeces were carefully stripped. The faecal samples, ingredient samples, and the diets were subjected to chemical analysis to determine the content of yttrium, protein (nitrogen) and energy. Diet apparent digestibiltiy coefficients (DADC) were determined, and these DADC values were used to derive the ingredient apparent digestibiltiy coefficients (IADC) using the diet substitution approach methodology. Ingredient protein digesitbilities ranged from 82.9 % to 112.3 % in snubnose pomano and were typically higher for soybean meal (Sparos Lda), whereas in mangrove red snapper the ingredient protein digestibilities ranged between 52.1 % and 99.9 % and were typically higher for corn gluten meal (Arabian Agricultural Services Company, ARASCO). Ingredient energy digesitbilities for snubnose pompano ranged from 55.2 % to 115.6 % and were typically highest for wheat gluten (National Aquaculture, NAQUA), whereas ingredient energy digestibilities ranged between 40.3 % and 93.3 % in manrove red snapper and were typically higher for fishmeal (United Marine Products, UMP). In comparison between the two species, the analysis revealed a weak correlation in both diet and ingredient digestibilities for protein and energy. Consequently, the use of digestibility data within species at the same trophic level necessitates a prior assessment when other factors are involved.