Abstract
The present study conducted at 10.21±0.27°C water temperature in freshwater recirculating aquaculture systems (RAS) to observe the temporal variations in the digestive enzyme activities including pepsin, trypsin, amylase and lipase of Black Sea salmon (Salmo labrax). Seventh filial generation (F7) of Black Sea salmon (Salmo labrax) with average initial weights of 69.85±10.08 g were by hand fed three times daily until apparent satiation. At the end of the 75-day trial the samples were dissected that reached a weight of 179.17±31.08 g at 45th minute, 3rd, 6th, 12th, 24th, 36th, 48th, 72nd and 96nd hours post feeding. In all enzyme groups, the third hour after feeding was recorded as the time when the highest levels were observed. However, enzyme activities decreased gradually as the time after feeding was prolonged. In the nutrition studies to be conducted at a suboptimal temperature in RAS, gut sampling of Black Sea salmon can be taken at 3rd hour after feeding. For a better understanding of digestive enzyme activity for this species, however, different sections of the digestive system should be comprehensively monitored including different temperature conditions.
Highlights
The digestive system of fish covers the region from mouth to anus
In the nutrition studies to be conducted at a suboptimal temperature in recirculating aquaculture systems (RAS), gut sampling of Black Sea salmon can be taken at 3rd hour after feeding
Our study demonstrated that trypsin, pepsin, amylase, and lipase enzymes increased from 45th minute to 3rd-hour post feeding, but decreased after 3rd hour
Summary
The digestive system of fish covers the region from mouth to anus. This anatomical structure is usually divided into headgut, foregut, midgut and hindgut (Floris, 2010). Chemical digestion of feeds starts in the foregut and continues in the midgut, even the midgut is where absorption takes place (Banan Khojasteh, 2012). Fish increase feed efficiency by digesting nutrients in the feed with the help of digestive enzymes (Shabana et al, 2019). The degradation of nutrients in the alimentary canal of fish is mostly dependent on the enzymes present (Hani et al, 2018).
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