Dietary Lactosucrose Affects Calcium Content in Scales of Juvenile Red Sea Bream Pagrus major under Artificial Rearing

Abstract

Some dietary oligosaccharides increase bone calcium content, often depending on hind- gut fermentation of the saccharide in mammals. Dietary lactosucrose, an indigestible and ferment- able oligosaccharides, also stimulates osteogenesis in mammals. This sugar is also fermented by gut microbes of a teleost, red sea bream Pagrus major. However, we do not know the effect of this sugar on the calcium metabolism of teleosts. If dietary lactosucrose affects calcium metabolism in the fish, calcium content in the bone or scales should be modified by this saccharide. Therefore, we tested the effect of dietary lactosucrose on calcium content of vertebrae and scales in red sea bream under artificial rearing for four months. Since the lactosucrose product we added to the diet included 57% lactosucrose and 20% lactose, we added a lactose-fed group to elucidate the influence of lactosucrose by itself. Fish fed lactosucrose had lower body weight gain than those fed control or lactose diet. Fish fed lactosucrose had greater calcium content in scales than did control fish. However, fish fed lactose had greater vertebral calcium and indifferent scale calcium when com pared with control fish. The above results suggest that dietary lactosucrose, but not the associated lactose, increased calcium concentration in scales. It is likely that indigestible and fermentable sac harides such as lactosucrose increase calcium retention in the hard tissue not only in mammals but also in marine teleosts.