Evaluation of protein and lipid ingredients through in vitro digestibility for tropical gar (Atractosteus tropicus) juveniles

Tropical gar (Atractosteus tropicus) is an ecologically, culturally, economically, and scientifically important species. Therefore, it is essential to know the available resources to design feeds for the culture of this species. This study evaluated the in vitro digestibility of meals and oils commonly used in aquaculture, using crude extract of the stomach and intestines of A. tropicus juveniles. We used the pH stat titration system to determine the degree of hydrolysis (DH%), the concentration of amino acids released (mg g of [meal.sup.-1]), and the speed of hydrolysis (SH%) of various animal and vegetable ingredients. The relative digestibility of each protein ingredient was calculated using bovine hemoglobin for acid digestion and Hammersten bovine casein for the alkaline phase as reference ingredients (100% digestibility). For lipid ingredients, fish oil was used as a reference. The highest relative digestibility for protein ingredients was observed with fish, crustaceans, beef, poultry meat and offal, and beef blood meals. The best lipid SH was observed with soybean lecithin and cod liver, soybean, olive, maize, and canola oils. It is possible to use a wide variety of terrestrial animal proteins and vegetable oils for manufacturing a diet for A. tropicus rearing.