Abstract
AbstractCurrently, studies reporting the digestibility of carbohydrates, starch and especially non‐starch polysaccharides (NSP) in fish are scarce. Carbohydrate digestibility in the diet is largely dependent upon carbohydrate composition (starch vs. NSP). NSP are often considered to be indigestible and thus of no nutritional value. The present study reviews carbohydrates in fish feed, distinguishing between total carbohydrate, starch and NSP. Besides a qualitative approach, a meta‐analysis was performed, compiling available data from digestibility studies on tilapia. Our meta‐analysis confirms the negative effect of NSP on performance (FCR) and nutrient digestibility (crude protein, fat and energy). However, an average NSP digestibility of 24.3% was calculated in 95 cases. Out of these 95 cases, 88% of them showed a positive NSP digestibility. NSP digestibility was shown to contribute to energy digestibility. The digestion of NSP in fish is associated with fermentation in the gut, producing beneficial volatile fatty acids that are rapidly absorbed by the colonic lumen. Therefore, in diet formulation, digestibility and thus energy originating from NSP should be taken into consideration because NSP contribute to the energy needs of fish, here tilapia. Besides being an energy source, specific types of NSP may have immune‐modulating and prebiotic effects and may be increasingly added to fish feed as modulators of fish health. We suggest that NSP is potentially (partly) digested by a wide range of fish species, especially by warm‐water species with a long gut adapted to feeding on plant matter, as these factors favour gut fermentation.
Highlights
Many studies have been performed with tilapia (Oreochromis spp.), comparing digestibility across a wide range of plant ingredients used as substitutes for dietary fishmeal and oil
The large differences in CHO digestibility between studies are mainly attributed to the dietary inclusion level of non-starch polysaccharides (NSP), because NSP is poorly digested compared to starch
The presented metaanalysis allows us to assume that NSP digestibility occurred in many tilapia studies (88%)
Summary
Many studies have been performed with tilapia (Oreochromis spp.), comparing digestibility across a wide range of plant ingredients used as substitutes for dietary fishmeal and oil These studies use a reference diet with a particular percentage of plant ingredients, such as soya bean meal; linseed meal; canola meal; cottonseed meal; sunflower meal; wheat middlings; corn gluten; rice bran; barley; and rye (Sintayehu et al 1996; Degani et al 1997; Schneider et al 2004; Ko€pru€cu€ & O€ zdemir 2005; Gaber 2006; Dong et al 2010; Obirikorang et al 2015). A more recent study using Nile tilapia by Haidar et al (2016) showed a digestibility between 41% and 73%, depending on the feeding level, for a diet enriched with dried distillers grains with solubles from wheat (DDGS)
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