Palatability of Protein Hydrolysates from Industrial Byproducts for Nile Tilapia Juveniles

SIMPLE SUMMARY: Aquaculture is highlighted as one of the most important activities to generate food with a sustainable character. Developing the production chain as a whole is considerably challenging, especially aiming to sustain its constant growth, thus studies regarding alternative feeds are required in order to meet the nutritional demands of this species. The protein ingredients are responsible for the larger share of this cost at 40–70% of the total expenses, and among protein sources, fishmeal is the most used in fish feeds. Improving the use of these byproducts (e.g., from poultry and swine productions) by adopting optimizing technologies represents an environmental, economic, and social alternative. In this sense, this study aimed at determining the palatability of protein hydrolysates made of swine liver, swine mucosa, poultry byproducts, and feathers for Nile tilapia juveniles. Protein hydrolysates increased the final consumption of pellets in comparison to fishmeal and provided the highest palatability index without altering the feeding behavior. Protein hydrolysates from byproducts from the industry of poultry and swine can be used in a sustainable way in diets for Nile tilapia juveniles in replacement of fishmeal. ABSTRACT: This study was performed with the aim of determining the palatability of diets containing poultry and swine protein hydrolysates for Nile tilapia. Five experimental diets were made with a 5% inclusion level of fishmeal (FPE), poultry protein hydrolysate (PHF), liquid swine hydrolysate (PHS), feather protein hydrolysate (PHP), and swine mucosa hydrolysate (PHM). Five juveniles (2.81 ± 0.17 g) were placed in 10 L aquariums and fed five times a day after a raffle of offered diets. In each feeding throughout the day, 30 pellets were offered per fish. The experimental design was completely randomized, with five replicates per day. A three-minute footage period was established for each feeding with a digital camera. The following feeding behaviors were observed: time to capture the first pellet, number of pellet rejections, number of approaches without capturing the pellet, and number of consumed pellets. No observed parameters presented significant differences (p > 0.05). PHF provided a palatability index of 12.27%, while PHM had an index of 9.33%, PHF of 8.77%, and PHP of 7.74%. Both diets PHS and PHM increased the final consumption of pellets in comparison to FPE by more than 10%, despite the absence of a significant effect.