Comparison of the effects of the prebiotics (Bio-Mos^® and β-1,3-D-glucan) and the customised probiotics (Pseudomonas synxantha and P. aeruginosa) on the culture of juvenile western king prawns (Penaeus latisulcatus Kishinouye, 1896)

Abstract

The present study investigated the effects of dietary immunostimulants on the growth, survival and immune responses of juvenile western king prawns (Penaeus latisulcatus). The immunostimulants used were two prebiotics Bio-Mos^® and β-1,3-D-glucan and two customised probiotics Pseudomonas synxantha and P. aeruginosa. The prawn juveniles (4.63 ± 0.39 g) were fed the formulated feed (control), supplemented with Bio-Mos^® at 0.5%, β-1,3-D-glucan at 0.2% and a combination of two probiotics (10⁵ CFU/mL at 50:50 v/v) at 20 mL/kg for 84 days of culture. The specific growth rate (SGR), survival and food conversion ratio (FCR) were higher in the prawns fed the immunostimulants than in the control. Although no significant effects on the SGR, survival and FCR were found when the prawns were fed either any prebiotics or probiotics, the higher survival was observed in the prawns fed the probiotics, while the higher SGR and lower FCR were observed in the prawns fed β-1,3-D-glucan, which had the most influence in increasing the surface structure of the prawn intestines. The healthier prawns showed the higher total haemocyte count (THC), the lowest clotting time and lowest bacterial load in the haemolymph when they were fed the probiotics. Continuous supplementation with the immunostimulants to the prawns for 84 days showed considerable improvement in the growth, survival and immune response of the prawns.

Introduction

The western king prawn, Penaeus latisulcatus, is one of the most popular species in the Indo-West Pacific region (Dore and Frimodt, 1987). Recent studies on the cultivation of this species have been undertaken in Australia by Sang and Fotedar, 2004a, Sang and Fotedar, 2004b, Prangnell and Fotedar, 2005, Prangnell and Fotedar, 2006, Prangnell (2007), Hai et al., 2007, Hai et al., 2009. As the regular use of antibiotics and chemicals as preventative and curative measures for disease leads to drug-resistant bacteria and harmful effects on the environment (Bachère, 2000, Bachère, 2003), alternatives to antibiotics and chemicals to improve the quality and sustainability of aquaculture production have been seen as desirable (Rengpipat et al., 1998, Meunpol et al., 2003, Vaseeharan and Ramasamy, 2003, Li et al., in press). The use of immunostimulants such as prebiotics and probiotics has been considered (Bachère, 2003).

Both prebiotics Bio-Mos^® and β-1,3-glucan are two commercially available products, derived from the cell wall of yeast Saccharomyces cerevisiae (Couso et al., 2003, Waldroup et al., 2003), in which Bio-Mos^® were recently applied in the animal husbandry industry and have shown promise in suppressing enteric pathogens and modulating the immune response of chickens and turkeys (Iji et al., 2001, Valancony et al., 2001, Waldroup et al., 2003, Kocher et al., 2005). Bio-Mos^® also enhanced the growth and FCR of early weaned pigs (Davis et al., 2000) and pig productivity (Maribo, 2003). There are a few publications on the use of Bio-Mos^® on chickens and pigs, but no reports of its effectiveness have been found in the culture of western king prawns. In addition, β-1,3-glucan has successfully enhanced resistance against bacterial and viral infections (Sung et al., 1998, Chang et al., 2003, López et al., 2003), used for preventing or reducing animal mortalities (Couso et al., 2003), and has been proven to modulate the activity of phagocytes and other components of the innate immune system in both fish and mammals (Di Luzio, 1985, Robertsen et al., 1994). The influence of glucans on the immune function and disease resistance in fish has been reviewed (Sakai, 1999), but the effect of β-1,3-D-glucan on western king prawns has not been investigated.

Probiotics are used as water additives or as feed supplements (Moriarty, 1998, Skjermo and Vadstein, 1999). Previous applications of probiotics have proved beneficial to the host by improving growth, survival and health (Moriarty, 1998, Skjermo and Vadstein, 1999). Our previous studies demonstrated that P. synxantha and P. aeruginosa are potential probiotics for use in the culture of western king prawns (Hai et al., 2007, Hai et al., 2009).

This study was conducted on juvenile western king prawns to compare the effects of the two commercially available prebiotics Bio-Mos^®, β-1,3-glucan and the previously customised probiotics Pseudomonas synxantha and P. aeruginosa (Hai et al., 2007) using the physiological response (SGR, survival, probiotic load in the intestine, haemolymph clotting time, surface structures of the intestines) and the immune response (the THC, hyalinocytes (HC), semi-granulocytes (SGC) and granulocytes (GC), and bacterial load in the haemolymph) of the prawns.