The aim of this study was to gain insight into how Nile tilapia (Oreochromis niloticus) regulate feed and energy
intake in response to diets low and high in starch and cellulose. It was hypothesized that high-starch diets
would reduce feed intake due to the effect of high blood glucose level, and that stomach volume may limit
feed intake of fish fed diets low in energy. Four experimental diets, low starch–no cellulose inclusion, high
starch–no cellulose inclusion, low starch–with cellulose inclusion, and high starch–with cellulose inclusion,
were formulated. The high-starch diets and diets with cellulose inclusion were 17.5% more energy-diluted
than the low-starch diets and diets without cellulose inclusion, respectively. Male tilapia were fed to apparent
satiation for six weeks. Feed and digestible energy intake of fish fed diets with cellulose inclusion increased
and decreased by 8.3% and 5.5%, respectively, compared to fish fed diets without cellulose inclusion. This
suggests the role of stomach volume in restricting feed consumption. Fish fed high-starch diets achieved only
0.5% more feed intake and 13.9% less digestible energy intake than fish fed low-starch diets. The lower
increase in feed intake and higher decrease in digestible energy intake offish fed high-starch diets than offish
fed diets with cellulose inclusion suggests that high blood glucose suppresses feed intake in Nile tilapia. An
alternative explanation for the differences in feed and digestible energy intake of fish fed different diets was
based on the fact that heat production was not influenced by starch nor cellulose-inclusion levels. Thus, under
satiation feeding, oxygen uptake capacity may determine feed and digestible energy intake infish rather than
blood glucose or stomach volume.