26 Feed Technology
A mix of free amino acids enhances growth, digestive enzyme activities, fillet composition, antioxidant and immune responses of juvenile Nile tilapia The dietary supplementation in feeds showed better growth parameters and biomass as well as feed conversion ratio reduction demonstrating how the mix acts as a sustainable and efficient feed ingredient By Pierrick Kersanté, Eakapol Wangkahart and Guillaume Le Reste
F
ree amino acids are efficient key nutrients which can improve aquatic species farming performances. More than 60 studies were recently conducted by BCF Life Sciences (France) in partnership with research centres, universities and farms. Most of them underline positive effects of Kera-Stim®50, a natural mix of free amino acids (MFAA) on zootechnical parameters for shrimp (Le Reste et al., 2019).
effects on the digestive enzyme activities. Amylase, protease and lipase in fish intestine were significantly increased with the use of MFAA. Antioxidative status of fish was measured by determination of non-specific immune enzymes in fish serum: superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GRD).
Complementary works conducted in partnership with Concepto Azul-Incabiotec, Peru, underline positive effects of this MFAA on survival under bacteriological and viral challenges for shrimp (Kersanté et al., 2021). In addition, numerous applications in shrimp farms underline positive effects of this MFAA supplementation on feed not only during normal conditions but also in the case of outbreaks of white faeces, a reduced impact of this syndrome and a faster recovery.
Results show significantly higher activity levels. We also observed significant improvements of innate immune response of fish serum such as lysozyme (LZM), myeloperoxidase (MPO) and catalase (CAT) activities. It is noteworthy that, in correlation with growth performances, MFAA supplementation on feed generates significant higher levels of the digestive, antioxidative and innate immune response enzymatic activities of Nile tilapia. We recently published these research results in the journal Aquaculture (Wangkahart et al., 2022).
With these positive observations and to better identify MFAA effects on antioxidant and immune responses for fish, we conducted a trial in partnership with Mahasarakham University, Thailand. Here, 450 healthy tilapia juveniles were randomly allocated to cages, at 30 fish per cage and three replicates per treatment. Animals were fed a control and four treatment diets; (control+0.25% (MFAA0.25), control+0.50% (MFAA0.50), control+0.75% (MFAA0.75) and control+1.00% (MFAA1.00) for 8 weeks with application of the MFAA into the pellet mix. MFAA supplementation of the feed significantly influenced zootechnical performances, with increase of growth parameters, biomass and feed conversion ratio (FCR) reduction. In regard to these parameters, we noted positive July/August 2022 AQUA Culture Asia Pacific
Animal husbandry and feeding protocol
The 450 healthy tilapia juveniles (Oreochromis niloticus), 4.76 ± 0.05g initial weight (IW) were purchased from Mahasarakham province, Thailand. The fish were acclimatised to laboratory conditions in circular fibreglass tanks for 2 weeks, in the aquarium of the Division of Fisheries, Mahasarakham University. During this period, fish were fed with a commercial diet containing 32% crude protein and 4% fat (Charoen Pokphand Foods, Thailand). After acclimatisation, fish were allocated to 15 floating cages (2x1.5x1.5m) in five triplicate groups at a stocking density of 30 fish per cage, in an open circulatory freshwater system.
