Protein sparing effects of energy sources in diets of fishes

Abstract

Studies on Protein sparing effects of carbohydrate and lipid were carried out in Clarias gariepinus (African catfish) fingerlings (2.50 – 8.32 ±0.04g) and Oreochromis niloticus (Nile Tilapia) fingerlings (8.05 ±0.05g). Three sources of carbohydrate (corn starch, corn fibre and glucose D) and lipid (groundnut oil, palm oil and fish oil) and a protein source (Fishmeal) were formulated and fed to the two species of fish (Catfish and Tilapia) in feeding trials that spanned 8 weeks for each of the experiment. The lipid (L) and protein (P) were in ratios designated as 10L:40P, 15L:35P and 20L:30P for lipid based diets and C5:30P, C10:25P and C20:20P for carbohydrate based diets for C. gariepinus. The tilapia diets consist of 15L:25P, 10L:30P, 5L:35P and C10:30P, C30:25P, C50:20P for both the lipid and carbohydrate sources. There were significant differences (P<0.05) among the treatments for the two species in their mean weight gains (MWG), specific growth rates (SGR), feed conversion ratios (FCR), protein efficiency ratios (PER) and apparent net protein utilizations (ANPU) which resulted in protein sparing of various non-protein sources fed. In C. gariepinus, glucose and corn starch spared protein at 20 and 10 % inclusion levels thereby lowering the crude protein inclusion levels to 20 and 25 % respectively from 30%. The groundnut oil and palm oil also spared protein at 20 and 15 % lowering crude protein from 40 % to 30 and 35 % respectively. Corn starch was found to spare protein for growth in O. niloticus, at 30 % thereby lowering crude protein inclusion level to 25 % from 30 %; while, fish oil was found to spare protein better than other lipid sources at 10 % inclusion level, reducing the crude protein level to 30 % from 35 %. The derived digestible protein sparing effects of digestible carbohydrate in C. gariepinus was found to be 9.78 : 16.77 digestible glucose : digestible protein instead of the gross diet fed (20 : 20) glucose : protein ratio and 4.28 : 20.95 corn starch instead of 10 : 25 carbohydrate/protein (C/P) ratio fed. The derived digestible lipid sparing effects of digestible protein in C. gariepinus was found to be 16.80 : 25.22 ratio for groundnut oil instead of 20 : 30 gross diet fed and 12.87 : 29.52 palm oil instead of 15 : 35 gross diet fed. In O. niloticus, the derived digestible corn starch that spared digestible protein was found to be 12.72 : 19.75 instead of the gross 30 : 25 C/P ratio fed. However, the fish oil that spared protein in O. niloticus was found to be 8.45 : 25.36 as derived instead of the 10 : 30 L/P ratio fed. From the study, the protein sparing effects of carbohydrate and lipid in the two species of fish tested revealed protein sparing effects of non-protein sources for energy thereby expending available protein for growth.