## 4 Discussion  
The intestinal nutrient uptake is highly dependent upon the interaction between digestive secretions and the condition of the absorptive surface [52]. We show here that flaxseed meal supplementation had beneficial effects in the duodenum and the jejunum morphology, characterised by a significant increase in villus height, probably leading to increased nutrient adsorption. Absorptive efficiency is controlled by the characteristics of the intestinal absorptive surface [53]. Morphologically, crypt depth and intestinal villus length are indicative of the intestinal absorptive capacity. High intestinal villus length triggers an increase in the mucosal surface area, which, in our study, may be due to the PUFA composition of flaxseed meal, as previously reported [54]. Digestion mediates the relation between animals and their environment [55]. Indeed, the digestive system's efficiency in extracting energy from nutrients is influenced by hydrolysis rates, fermentation and absorption digesta retention times, and the gastrointestinal tract's surface area and volume [56]. The enterocyte membrane-bound enzymes hydrolyze food molecules that arrive in the small intestine [57] from the upper digestive segments [56]. Increased effectiveness of birds' endogenous enzymes allows for the gel forms characteristic of soluble fibers to be broken down more efficiently, hence improving starch, protein, fat, and amino acid digestibility [58; 35]. Amylase acts on starch, catalyzing hydrolysis of the \(\alpha\) 1-4 glycosidic bond, generating maltose as an end product and thereby improving its digestibility. In our study, the activity of alpha-amylase was increased in the duodenum and jejunum when compared to that for the control group. This could be due to the important content of linoleic acid in the flaxseeds, a potent activator of amylase secretion by pancreatic acinar cells [59]. On the other hand, oleic and linoleic acids showed an important inhibitory action against \(\alpha\)-glucosidase activity [60]. This could explain the decrease in maltose activity in the duodenum, even as the villus length increased. In the jejunum, this enzymatic activity was higher in the E group as compared to control one, this being correlated with the greater villus length. Probably due to the high secretion of amylase, its activity in the duodenum was also inhibited to a certain extent, but it remained a little bit higher than that in the control group. The other brush border disaccharidase, i.e., invertase, which catalyzes the hydrolysis of the \(\alpha\) 1-2 glycosidic bond between an \(\alpha\) glucose unit and a \(\beta\) fructose one, showed increased activity in both analyzed intestinal segments, suggesting a direct correlation between the enzyme molecules and the increasing length of the villi in the E group compared to the control group. Trypsin is a proteolytic enzyme that hydrolyses protein and peptides and accounts for most peptidase activity of the brush border membrane [56]. In our study, there was no significant variation of trypsin activity in the duodenum and jejunum in group E compared to the control group. Our results regarding this enzyme activity were in agreement with those of [PERSON] et al. [61], showing that the free fatty acid content does not interfere with its pancreatic secretion and/or activity. Lipids are the main energy source for broilers [62] and enter the duodenum intact. The presence of food in this part of the intestine stimulates the secretion of cholecyst, triggering the contraction of the gall bladder and exocrine pancreas secretion. In the presence of bile acids, micelles are formed, which are probably composed mainly of PUFA. Lipase acts at the lipid-water interface of micelles, being stabilized by coliage [63]. According to our data, there was no significant difference between the lipase specific activity levels in the E and control groups.