Effect of dietary B-glucan on the growth performance of freshwater prawns Macrobrachium rosenbergii

Abstract

β-glucans are naturally occurring linear unbranched homopolysaccharides that contain only glucose, linked by glycosidic bonds, as structural components. Dietary β-glucan is found to enhance the growth and immunity of many animal species including a number of aquatic species. Giant freshwater prawn (Macrobrachium rosenbergii) culture has been developing rapidly over the last few years in Sri Lanka. One of the major constraints facing this industry is lack of a balanced commercial feed to obtain optimal body size in commercial culture systems. In this regard, β-glucan can be used as a growth promoter in freshwater prawn feed. However, up to now, there have been no studies on the use of β-glucan as a growth promoter in freshwater prawn farming. Thus, the present study was conducted to investigate the effect of dietary β-glucan derived from yeast on the growth performance of freshwater prawns.

Five different experimental feeds were prepared using supplements with different percentages of β-glucan (0, 0.1, 0.3, 0.5, 1% w/w). All five types of feed had the same composition except for the percentage of β-glucan. Feeding trials were conducted in duplicate in ten different fibre-glass tanks. Thirty post-larvae of M. rosenbergii with an initial body length of 9.0 mm were allocated to each treatment and fed with experimental feed twice a day for 19 weeks. The total body length of 26% prawns in each tank was measured at 5, 10, 15 and 19 weeks to calculate the growth rate. Statistical analysis showed that dietary β-glucan significantly (P < 0.05) increased the growth rate of giant freshwater prawns. The highest growth rate was achieved with 1% β-glucan. Further, the body length of prawns fed 1% β- glucan had a significant relationship (P < 0.05) with the age of prawns.

The present study concludes that dietary β-glucan significantly enhances the growth of fresh water prawns.