Abstract. Mohammed FA, Yousif RA, Hilal FM, Adam RA, Ahmed TK. 2020. The effect of dietary methionine levels on growth, feed conversion and protein retention efficiency of Nile Tilapia (Oreochromis niloticus) fingerlings. Nusantara Bioscience 12: 21-27. A 49 days feeding trial was conducted to evaluate growth, feed utilization and body composition of Nile tilapia Oreochromis niloticus (4.30±0.01 g), fed five isonitrogenous (32 g 100 g-1 crude protein) and isoenergetic (14.51 kJ g-1 Gross energy) practical diets and five levels of methionine supplementation (0.5, 1, 1.5, 2 and 2.5 g 100 g-1). The experimental design was completely randomized with five treatments and three replicates. Fish were stocked in triplicate groups of 20 fish held in 70 L flow-through tanks (water volume 55 L) and fed twice daily (08:00 am and 04:30 pm) to apparent satiation. When absolute weight gain (AWG; g fish-1), feed conversion ratio, protein deposition (g fish-1) and protein retention efficiency (%) data were subjected to second-degree polynomial regression analysis 95% of the plateau of the above parameters was achieved at dietary methionine concentrations between 1.4-1.5 g 100 g-1 dry diet or 0.09-0.10 g methionine kJ-1 GE. Corresponding to 4.4-4.7 g 100 g-1 of the dietary protein. Based on these results, dietary methionine requirement for Nile tilapia Oreochromis niloticus is recommended 1.4-1.5 g 100 g-1 diet.

The present study deals with the estimation of gill surface area for orange spotted grouper (Epinephelus coioides) collected from Iraqi marine water, north west Arabian Gulf. In the laboratory, fishes were separated in to five different length groups ranging from 200-325 mm and weight range of 108.8-582.2g. Absolute and relative total gill surface area (GSA) were estimated for 33 fish from different lengths. Statistical analysis of results revealed that there were significant differences (P<0.05) between total length of gill filaments (TFL) in different length groups, while there were no significant differences (P>0.05) between secondary lamellae (Bl) in different length groups. Statistical analysis showed also that there were significant differences (P<0.05) between secondary lamellae numbers (N) in some length groups.Statistical analysis of results showed significant differences (P<0.05) between absolute surface area of most different length groups, and also significant differences (P<0.05) between relative surface area of different length groups except group of 276-300 mm with group of 301-325 mm. Results showed positive relationship between absolute surface area and length groups with significant correlation, and negative relationship between relative surface area and length groups with significant correlation (-0.989).It seemed that the factor L had a direct effect on the values of absolute respiratory area and Fish weight had an inverse effecte on the the relative area of the gills.

he aim of this work is to study the effects of cereal type (corn or wheat-based diets), and multicarbohydrase enzyme supplementation to broiler diets containing recommended, intermediate (-100) or low (-150) Kcal/kg ME energy levels and their interactions on broiler performance, protein and energy efficiency ratios, nutrient digestibility, carcass traits and some blood measurements. A total of 480, seven day-old unsexed Cobb500 broiler chicks of 160 g average body weight were randomly divided into eight experimental treatments and three replicates per treatment group. The experiment consisted of 3 growing phases {starter (7-14 d), grower (15-28 d) and finisher (29-42 d)}. Diets were formulated to contain 21, 19 and 18 % protein levels and 2988, 3083 and 3176 kcal/kg ME during the starter, grower and finisher phases, respectively. During each growing phase, each group was fed on one of the following experimental diets: corn-soybean based diet without supplementation(C), wheat-soybean based diet without supplementation (W), corn-soybean based diet supplemented with enzymes cocktail at level of 50 g/ 100 kg diet (C+), wheat-soybean based diet supplemented with enzymes cocktail at level of 50 g/ 100 kg diet (W+), low energy (100 kcal) corn-soybean based diet supplemented with enzymes cocktail at level of 50 g /100 kg diet (LC100+), low energy (-100 kcal) wheat-soybean based diet supplemented with enzymes cocktail at level of 50 g /100 kg diet (LW100+), low energy (150 kcal) cornsoybean based diet supplemented with enzymes cocktail at level of 50 g /100 kg diet (LC150+) or low energy (-150 kcal) wheatsoybean based diet supplemented with enzymes cocktail at level of 50 g /100 kg diet (LW150+). The carbohydrase enzymes cocktail supplement supplied per 1 g, 3000 U α-galactosidase, 5000 U βmannanase 2500 U xylanase, 1500 U βglucanase and 1000U cellulose. The obtained results could be summarized as follows: birds fed the corn-based diets had overall superior weight gain, feed consumption, feed conversion ratio, nutrient digestibility and protein and energy conversion ratio compared with those fed the wheat-based diets. Enzyme cocktail supplementation to corn or wheat based diets improved all tested parameter cited above. No significant differences were found between the low ME enzymes supplemented diets (L100+ and L150+) and their respective control groups for body weight gain during the overall period. Enzymes supplementation to low energy diets compensate for lowering energy level by increasing feed consumption. Birds fed corn based diets or enzyme supplemented diets, irrespective of cereal type, had significantly high blood plasma glucose level. On the other hand, neither cereal type nor enzyme supplementation had a significant effect on blood plasma total proteins and total lipids. Chicks fed corn based diet improved EPEI (European production efficiency index) by 18.21 % compared to those fed wheat based diet and enzyme supplementation to corn or wheat based diets improved significantly EPEI and the improvement was mor...