This study investigated the effects of diet supplementation
with poly-b-hydroxybutyrate (PHB) on growth performance, digestive enzyme activity, lipid metabolism, mineral
uptake and bacterial challenge of the rainbow trout fry
(initial weight: 111.3 13.7 mg) during a 6-week experimental period. In the experimental set-up, the commercial
diet of rainbow trout fry was replaced with 0.5%, 1% and
2% PHB. The results of our work showed that the replacing of diets with PHB in experimental treatments decreases
the weight of rainbow trout fry during the first 2 weeks
before significantly increasing final weight at the end of the
6-week period. PHB also improved digestive enzyme activity in experimental treatments. The highest total protease,
pepsin activity and pancreatic enzyme secretion were
observed with the 0.5% PHB treatment. A higher concentration of Na and K was observed in the whole body of
the fry fed on 1% and 2% PHB-supplemented diets.
Enhanced survival rates occurred in all groups of fry after
bath exposure to Yersinia ruckeri compared to rates in
those fed the control diet. Our results suggest that the diet
supplemented with PHB may improve growth performance,
digestive enzyme activity and the functioning of the
immune system. These positive effects could be considered
for new applications in aquaculture.
