Effects of increasing the dietary lipid levels on the growth performance, body composition and digestive enzyme activities of the teleost pejerrey (Odontesthes bonariensis)

• The increase of dietary lipids affected the growth performance of pejerrey.
• Muscle fatty acid composition was differentially regulated by dietary lipids.
• High dietary lipid levels negatively affected specific digestive enzyme activities.
• Dietary lipid contents of approximately 10% might support the growth of pejerrey.

The present study aimed at determining the growth performance, body composition and digestive enzyme activities of pejerrey (Odontesthes bonariensis) juveniles fed with graded levels of dietary lipids: 6% (L6), 10% (L10) and 25% (L25). Following a 14-week growth trial, weight increase decreased in group L6. The protein productive value increased in groups L10 and L25, whereas group L10 showed the highest lipid productive value. Hepatosomatic and mesenteric fat indexes decreased in group L6. Body protein content decreased with the increase in dietary lipids (L6 > L10 > L25); whereas body lipid content, and nitrogen and energy retentions were the lowest in group L6. The muscle fatty acid composition was differentially regulated by the diets except EPA, DHA and n-3 PUFA contents. The total n-6 PUFA decreased in group L6. The n-3 PUFA tended to accumulate in the muscle of the fish; group L10 exhibiting the lowest accumulation rate. The total activity of neutral lipase was stimulated in group L25 whereas the specific activity of pancreatic lipase decreased in this same group. While group L6 showed the lowest total activity of alkaline proteases, group L10 showed the highest total activity of trypsin. A decrease in the specific activity of amylase in group L25 followed the decrease in dietary starch. In summary, 25% of dietary lipids did not have additional stimulatory effects on the digestive proteases activity compared to 10%, but negatively affected pancreatic lipase and trypsin activities. Moreover, the decrease of the latter in group L25 suggests that approximately 10% of dietary lipids might support the growth of pejerrey juveniles reared in captivity.