Isoenergetic Replacement of Fat by Starch in Diets for African Catfish (Clarias gariepinus): Effect on Water Fluxes in the Gastro Intestinal Tract

Abstract

The effect of an isoenergetic replacement of dietary fat by starch, on chyme characteristics and water fluxes in the gastro intestinal tract (GIT) was assessed. Adult African catfish (Clarias gariepinus) were fed a starch (SD) or fat (FD) diet and groups of fish were dissected at 2, 5 and 8 h after the consumption of a single meal. Chyme was collected quantitatively and was analysed for osmolality and dry matter (DM) content. Postprandial water fluxes were calculated, while using yttrium oxide (Y2O3) as an inert marker to account for the absorption of DM along the GIT. The largest differences in chyme characteristics between diets were observed in the stomach and decreased towards subsequent compartments. A high initial osmotic pressure was measured in the stomach for both diets (up to 498±2 mOsm kg−1) and was likely the driver for the endogeneous water influx to this compartment. Large additions of water were recorded to the stomach and proximal intestine for both diets and absorption of water took place in the mid- and distal intestine. Interestingly, the dietary treatment had an impact on water balance in the stomach and proximal intestine of the fish, but not in the mid- and distal intestine. A strong complementary relationship suggested that 59% of the water fluxes in the proximal intestine could be explained by previous additions to the stomach. Therefore, a higher dietary inclusion of starch led to a shift in water additions from the proximal intestine to the stomach. However, the sum of water additions to the GIT was not different between diets and was on average 6.52±0.85 ml water g−1 DM. The interactions between osmoregulation and digestion, in the GIT of fed freshwater fish, deserve further attention in future research.

The source of dietary non-protein energy affectsin vivoprotein digestion in African catfish (Clarias gariepinus)

“…The results for chyme DM content have been previously reported (Harter et al . ). A significant ( P < 0.05) diet effect on chyme viscosity was observed in the stomach and distal intestine, but not in the mid‐intestine.…”

“…The obtained results on the postprandial water fluxes in the GIT of African catfish are discussed in more detail by Harter et al . (). Results suggest that animals fed FAT had a higher average chyme DM in the stomach ( P < 0.002) compared to STARCH.…”

“…The results obtained on some of the performed measurements have been previously published in Harter et al . (), which addressed the kinetics of water fluxes along the GIT in response to dietary macronutrient composition. The present study focuses on the effect of NPE source on CP digestion.…”

Factors affecting the quantity and quality of faecal waste in striped catfish

“…Leenhouwers et al (2007b) showed a decrease in faecal dry matter with increasing dietary viscosity as a result of replacing different ingredients in African catfish and that influenced the removal of the faeces. In addition, there are some studies (Leenhouwers et al, 2007a;Harter et al, 2013) which observed that the variation in the characteristics of chyme related to the faecal characteristics.…”

“…Also, the requirement for water for fat emulsification may play a role, since viscous substances are known to bind water. However in Nile tilapia (Amirkolaie et al, 2006), African catfish (Harter et al, 2013) and also in striped catfish (Tran-Tu et al, 2019, submitted article) it has been shown that the viscosity of the chyme increase as it passages towards the distal intestine.…”