In commercial shrimp farming, feeding is one of the main costs. On the other hand, slow localization and ingestion of pellets by the shrimp lead to nutrient leaching and uneaten feed, causing a reduction in diet’s nutritional quality and environmental contamination . The attractability and palatability of commercial feeds can be improved through additives containing specific chemosensory cues that can be rapidly recognized and initiate ingestion by the shrimp . Shrimp feeding behaviour can play an important role in the assess ment of these novel sensory feed additives . Therefore , the development of automated protocols using tracking technologies is beginning to gain attention as an important tool for monitoring behaviours associated to feeding . The objective of this study was to evaluate shrimp feeding response to a commercial feed additive (Luctamax FPE AQUA, Lucta S.A.) via an automated video tracking software , benchmarking with diets of variable levels of attractability and palatability .
Litopenaeus vannamei juveniles (5.50 ± 2.20 g) were sourced to assess behaviour and feed intake responses to three control diets; basal (BC; without additives), negative ( NC; BC + 0.07M Quinine-HCl) and positive ( PC; BC + 3% Krill Meal) controls, and two diets containing the functional palatability enhancer (FPE) at two different concentrations , BC + 0.1% (FPE 0.1) and BC + 0.2% (FPE 0.2) . Non-moulting and 24-hours fasted shrimp were individually video recorded during 20 min, in consecutive days . Rectangular test arenas (78 x 20 x 20 cm; L x W x H) were equipped with a chamber where shrimp were acclimated 10 min before starting the recording, and a feeding area at the other end where 0.5 g of one of the test diets was dispensed. A video camera was setup directly above the test arena to record the entire system. Thirty-four v ideos were recorded for each test diet and analysed using EthoVision XT 17. A set of behavioural units were analysed by the software, generating metrics related to the attractability and palatability of each test diet . Besides , uneaten pellets were collected at the end of each recording and compared to the initial number for feed intake assessment. Statistical analysis was done by Generalized Linear Mixed Model, considering diet as a fixed factor and shrimp ID as random factor.
The PC and FPE 0.2 diets showed enhanced palatability, indicated by increase d time spent on the feeding area (Fig. 1a ), and attractability levels , suggested by reduced exploratory activity around the test arena, in comparison with the other diets . A n increased number of pellets eaten was also found in PC and FPE diets (Fig. 1b) . Results from this study highlight the improvement of attractability and palatability levels using 0.2% Luctamax FPE AQUA as a feed additive in L. vannamei diets and the feasibility of implementing automated shrimp feeding behaviour protocols for the industry.