Betaine is a feed enhancer for juvenile grouper ( Epinephelus fuscoguttatus ) as determined behaviourally

摘要

ABSTRACT The present study aimed to determine if betaine can function as a feeding stimulant or feed enhancer for the juvenile grouper, Epinephelus fuscoguttatus through a behavioural experiment with video recording. Agar gel pellet was used as the medium to deliver the chemical test substances ?￠???? betaine (BET), amino acids mixture (AAM) and mixtures of 1:1, 1:2, 1:3, 1:4, 1:5 BET?￠????+?￠????AAM to the fish. The pure agar gel (PAG) and feed extract pellets were used as the negative and positive control, respectively. From the recorded videos, two parameters were observed: (I) the pellet was consumed or rejected [ A ] ?￠???? if consumed, recorded 1; if rejected, recorded 0, and (II) frequency of the pellet has been captured before it was consumed or rejected and ignored [ B ], and the preference index was calculated through [ A ]/[ B ]. The PAG pellet was totally rejected by the fish (index's value?￠????=?￠????0). The index's values of BET and AAM were 0.17?￠???????±?￠????0.39 and 0.19?￠???????±?￠????0.31 (mean?￠???????±?￠????SD), respectively. No significant difference was found among the index's values of PAG, BET and AAM pellets. However, the index's values of all BET?￠????+?￠????AAM pellets (1:1?￠????1:5) were very high (0.60?￠????0.90), and were significantly higher than those of the PAG, BET and AAM pellets. No significant difference was found among the index's value of 1:1, 1:2, 1:3 and 1:4 BET?￠????+?￠????AAM treatments. These results concluded that betaine is a feed enhancer for the E.????fuscoguttatus and little amount of betaine supplementation is sufficient to enhance the flavour of amino acids mixture.