Understanding chemical sensitivity and preference of grouper to Amino Acids for aquafeed development

• Main Authors: Rossita Shapawi, Gunzo Kawamura, Lim, Leong Seng
• Format: Research Report
• Language: English
• Published: Universiti Malaysia Sabah 2013
• Subjects: SH Aquaculture. Fisheries. Angling
• Online Access: https://eprints.ums.edu.my/id/eprint/24576/1/Understanding%20chemical%20sensitivity%20and%20preference%20of%20grouper.pdf; https://eprints.ums.edu.my/id/eprint/24576/

Grouper aquaculture is expanding but most grouper farmers are challenged by high cost of feed input due to the dependency on the expensive fish meal. Soybean meal (SBM) has high potential to replace fish meal but at high inclusion levels, diets palatability is affected. The use of suitable feeding stimulant (via gustation) or attractant (via olfaction) in non-fish meal based diets might be able to Increase feed Intake. Amino adds and betaine are rommonly used as feeding stimulant and attractant in aquaculture feeds. Unfortunately, little Is known about the specific response of grouper to these substances. The present study aimed to investigate the chemical responses In the grouper (Epinephelus fuscoguttatus) to feeding stimulant and attractant and evaluate its potential to promote the intake on SBM-based diets through an electrophysiology (Experiment 1), two behavioural (Experiments 2 & 3) and a feeding experiments (Experiment 4). In experiment 1, cysteine was determined as the most sensitive amino add to the olfaction of grouper, followed by lysine and arginine at the concentration of 10·3 M through electro-olfactogram analysis. The threshold level of cysteine was also determined at 10·5 M. Experiment 2 was carried out to ronfirm the results of Experiment 1 through behavioural study. Cysteine yielded the highest frequency in both the swimming and food searching activities, indicating its suitability as food attractant. In this experiment, It was realized that olfaction may not play a very critical role In cultured grouper because they are visual feeder and food are always provided by the farmers. Besides, the decision In food ingestion is mediated by gustation. Consequently, identification of feeding stimulant Instead of attractant Is more appropriate for the cultured grouper. Therefore, Experiment 3 was ronducted to study the taste effect of betalne and the preference for amino adds In tiger grouper using video rerording and agar gel pellet as the delivery medium. It was determined that betaine functions best as a feed enhancer In grouper. Betaine Itself has low palatability but It enhanced the flavour of the amino. acids mixture (also low In palatability) and Improved the Intake of the agar gel pellet by the fish. Interestingly, only small amount of betalne was required to enhance the flavour of the amino adds mixture (betalne: amino adds mixture 1:4). Among all the amino adds tested, only amino add A was properly ingested by the fish. The fish aa:eptance for the amino acid A did not change with growth. In fact, the taste sensitivity for amino add A Improved with the size of fish. In experiment 4, an 8-week feeding trial was conducted to evaluate the potential of betaine and mixture of the selected amino acids to promote Intake of SBM-based diets In the grouper. Although the best performance was achieved by the fish fed control diet, supplementation of betaine and the amino adds mixture improved the feed intake and growth In fish fed SBM·based diets. The optimum supplementation level of betaine was also determined at 1.0% based on the higher feed Intake and fish growth In this treatment In addition, another two feeding experiments (Experiments 5 and 6) were <Dnclucted to further testify the effect of amino acid and feeding stimulant supplementations to promote feed Intake of grouper on SBM·based diet In Experiment s, fermented soybean ( tempeh -TMP) was used to replace SBM, and found that the optimum indusion level of TMP was 40%, which was sllghtly higher than SBM (30%). Ash fed diet with 40% TMP protein generally attained less enteritis than those fed SBM-based diet but the feed intake was low. In Experiment 6, supplementations of feeding stimulant and essential amino adds were found to Improve the feed Intake, growth performance and feed utilization of grouper fed TMP-based diet, although the optimum supplementation level of feeding stimulant remained to be determined because the source and quality of soybean product can Influence the diets palatability. In conclusion, narrow chemical sensitivity to spectrum of amino adds In the grouper is observed. The findings of the study suggest that the issue with low palatability In SBM-based diets In grouper aquaculture can be solved by the use of species-specific attractant and stimulant