The low salinity conditions in which Asian sea bass are usually grown allow them to grow quickly, but they also pose challenges. Two trials on young sea bass showed that yeast hydrolysate supplementation improved the growth performance of these fish.
Saccharomyces yeast hydrolysate is produced by strong acid hydrolysis, which effectively breaks down the yeast cell wall and converts its molecules into biologically active forms. In particular, the decrease in molecular size and the increase in molecular solubility lead to an increase in the bioavailability of gut microbes and intestinal mucosal immune cell receptors. The feed supplement used in the research is an epibiotic, a beneficial product derived from microorganisms, without any live microorganisms, and its biologically active molecules can be used for interaction. Recent research shows its benefits for Asian sea bass.
In cooperation with the Agricultural University of Thailand, two experiments were carried out at the University Contract Research Farm in Nakhon Pathom Province, Thailand to study the effect of adding yeast hydrolysate (Progut) to the diet on the performance of Asian sea bass (Lates calcarifer). The experiment was carried out in earthen ponds under low salinity conditions, which are common commercial production conditions for sea bass in Thailand.
In experiment 1, juvenile fish with an average weight of 13 grams were allocated to 12 cages, each with 30 fish, with a density of 5 fish/m3. The three diet treatments tested were a commercial type of control feed and the same feed with 0.15% or 0.30% feed additives. Four duplicate cages were randomly assigned to each diet. These fish were fed 3-5% of their body weight 3 times a day for 8 weeks (Figure 1). The fish's feed intake, weight gain, feed conversion ratio (FCR) and mortality were measured. At the end of the study, blood samples were taken from 5 fish in each cage for analysis of several immune-related variables. The length of intestinal villi was also measured from the same fish.
Figure 1-Experiment 1: Progut 0.15% and 0.30% 8-week juveniles.
In experiment 2, the starting weight of growing Asian sea bass was about 270 grams (+23 grams), and they were allocated to 20 cages, each with 10 fish, with a density of 5 fish/m3. There are 4 dietary treatments in the study, a commercial type of control feed and the same feed supplemented with 0.10%, 0.15% or 0.20% Progut. Five duplicate cages were randomly assigned to each treatment. Feed the fish 3 times a day, 3 – 5% of body weight for 12 weeks (Figure 2). The fish's feed intake, weight gain, FCR and mortality were measured. At the end of the study, blood samples were taken from 2 fish in each cage for analysis of several immune-related variables. The length of intestinal villi from the same fish was also measured.
Figure 2-Experiment 2: Fish was supplemented with 0.10%, 015% and 0.20% Progut for 12 weeks.
In the 8-week growth period of Experiment 1, the addition of yeast hydrolysate significantly increased the average daily weight gain of fish by 36%, and fish feed consumption increased by 28% on average (Table 1). In this study, yeast hydrolysate supplementation did not affect FCR or survival rate. The white blood cell count was the lowest in the group that received the higher dose components. Other measured immune parameters did not show significant differences between treatments.
The average intestinal villi length of the foregut was higher in the group receiving yeast hydrolysate than in the control group (Table 1).
In Experiment 2, the addition of Progut to the diet of growing sea bass under commercial field conditions significantly improved growth and FCR (Table 2). During the trial period, the effect of supplements on these performance parameters is increasing and is statistically significant during the 8 to 12 weeks of the trial. The survival rate of all treatment groups was 100%. In all fish groups fed Progut, superoxide dismutase (SOD) tends to be higher (p=0.068). As an antioxidant, SOD converts harmful superoxide radicals into oxygen and hydrogen peroxide.
In the 0.15 – 0.20% dose group, the activity of antimicrobial lysozyme was numerically higher. The other measured blood parameters did not differ between treatments. The average intestinal villi length of the foregut in the group receiving the product was higher than that in the control group.
These two trials have shown that yeast hydrolysate supplements can improve the feed intake and growth performance of Asian sea bass. In the growing fish, a significant increase in the feed conversion rate was observed, and the extent of the effect increased at the end of the study.
Judging from the effect on the length of intestinal villi and the enzyme SOD and lysozyme activity, the improved growth performance of yeast hydrolysate supplements may be mediated by its positive effects on intestinal morphology, immunity and killing pathogens.
In short, adding 0.1 – 0.2% of Progut can improve the growth performance of Asian sea bass, which may be beneficial to immunity and intestinal morphology.
Hebei Shuntian biotechnology Co.,Ltd.
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