The present study evaluated the effects of a commercial soy lecithin‐containing bioemulsifier Lysomax® on growth performance, feed utilization, haematology, immune response and gut histology of adult Nile tilapia (Oreochromis niloticus) fed soybean meal‐based diets, containing plant oil as a lipid source. This emulsifier was incorporated into four isonitrogenous (30% cp), isocaloric (17.5 MJ/kg) test diets, at 0 (control), 0.3, 0.6 and 0.9 g/kg feed. The diets were fed to triplicate groups of adult Nile tilapia, reared in a closed recirculating indoor system, at a daily rate of 3% of fish live weight, twice a day for 60 days. Growth rates, feed utilization efficiency, digestive enzymes activities, blood parameters, liver function enzymes and immunological responses were all boosted (p < .05) with increasing supplemental Lysomax up to 0.3 g/kg diet, followed by a significant retardation (p < .05) at 0.6 and 0.9 levels. Muscle n‐6 and n‐3 polyunsaturated fatty acids (PUFA) and n3/n6 ratio were also increased with increasing Lysomax up to 0.3 level and then levelled off with further increase in dietary Lysomax. The highest length and width of the intestinal microvilli and goblet cell counts were also found in the fish fed on 0.3 g Lysomax/kg diet. However, the quadratic regression analyses of the obtained results indicated that the maximum performance occurred at about 0.45 g/kg of dietary Lysomax. These results suggest that lecithin‐containing bioemulsifier Lysomax® can play a significant role in feed digestion and absorption and improving fish performance and innate immune response. About 0.45 g/kg diet would be sufficient for best performance and health status of farmed Nile tilapia.

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he present study was carried out at the experiment farm of faculty of agriculture, Ain Shams University. The aim of this experiment was to evaluate the effect of inclusion of guar meal (G) as a partial or total replacement for soybean meal (SM) in broiler diet on production performance and carcass traits of Ross broiler chickens. At 7 days of age, 125 unsexed broiler chicks (Ross 500) were divided into 5 treatments (25 birds each). Each treatment contained 5 replicates of 5 chicks each. The experimental treatments were: control diet (100% soybean meal, SM), T1 (87.5% SM+12.5% G), T2 (75%SM+25%G), T3 (50% SM+50% G) and T4 (100% G). Results obtained could be summarized as follows: 1-Replacement SM with G in broiler chick diets had a significant effect on live body weight gain, feed intake and feed conversion ratio. 2-Chicks fed 100% G diets gave the lowest results in live body weight gain, feed consumption and feed conversion ratio. 3-Replacement SM with G in broiler chicks gave significant effect regarding slaughter parameters, carcass parts (%), digestive tract length (cm/100g BW), some bone traits and some blood parameters. 4-Broiler chicks fed diets containing different levels of G gave the lowest economic and relative efficiency values when compared with the control. Generally, using guar meal as a replacement for soybean meal at the tested levels in this study may not be beneficial under practical conditions and further research is needed to determine a more accurate level of inclusion of guar meal for better performance and carcass characteristics.