| Exp.1 Effects of coarse buoyant supplementation on the buoyancy of feces,growth and intestinal health of Tilapia,Oreochromis niloticus×O.aureus The trial was conducted to evaluate the effects of positively buoyant dietary materials on growth,intestinal health,and fecal properties of tilapia,Oreochromis niloticus×O.aureus.The three buoyant materials with coarse particles(450-830 μm)were included in diets at 0(control),3,4 or 5%supplementation levels to feed tilapia juveniles(55.0 ± 1.0 g),and the growth,feed efficiencies,evacuation velocity,fecal floatability and intestinal histology were examined after 21 days feeding.In trial 1,the weight gain(WG)of the fish significantly decreased with the supplementation of 2%,3% cork,3% microball or 3% vermiculite(P<0.05),and the feed conversion ratio(FCR)was significantly increased by 3% cork and 3% vermiculite(P<0.05)when compared to the control.Cork-fed groups were observed to have more floating feces than microballand vermiculite-fed groups.Dietary cork significantly decreased the sinking velocity of diets and feces(P<0.05),but microball only decreased the sinking velocity of diets,and vermiculite(4%,5%)decreased the sinking velocity of feces(P<0.05).All buoyant materials supplemented groups showed lower WG and higher FCR than the control(P<0.05).The intestine evacuation velocity and villus height,crypt depth,muscle thickness of intestinal walls were decreased by the increasing buoyant materials in diets,and 5% microball group showed the lowest values among all groups.In conclusion,dietary cork,microball and vermiculite(3%-5%)negatively affect the growth performance and intestinal histology of tilapia,and diets with cork supplementation could decrease the density of feed and feces to produce floating feces.Exp.2 Effects of fine buoyant supplementation on the growth of Tilapia,Oreochromis niloticus×O.aureus The trial was conducted to evaluate the effects of fine buoyant supplementation on growth of tilapia,Oreochromis niloticus×O.aureus.Ten diets containing 0(control)1,2 or 3% fine particles(250-450 μm)of cork,expanded and vitrified microball,and expanded vermiculilite were fed to tilapia fry(5.0 ± 0.1 g)for 30 days to evaluate the effects on the growth and feeding efficiencies.The weight gain(WG)of the fish was significantly decreased by the supplementation of 2%,3% cork,3%microball or 3% vermiculite(P<0.05),and the feed conversion ratio(FCR)increased by 3% cork and 3% vermiculite(P<0.05)when compared to the control.In conclusion,dietary cork,microball and vermiculite(1%-3%)negatively affect the growth performance of tilapia.Exp.3 Effects of dietary cork,protease and guar gum on the buoyancy of feces,growth and intestinal health of Tilapia,Oreochromis niloticus×O.aureusThe present study was conducted to evaluate the effects of different particle size and level of dietary cork,and protease,guar gum supplementation on growth,intestinal health and fecal floatability of tilapia,Oreochromis niloticus×O.aureus.The cork with fine particles(30-40 mesh,0.45 mm-0.60 mm)and coarse particles(20-30 mesh,0.60 mm-0.83 mm)were included in diets at 0(control),2,3 or 4% supplementation levels,and175 mg/kg exogenous protease(P),3 g/kg guar gum(G)and 175 mg/kg protease + 3 g/kg guar gum(P+G)were supplemented in the 4% coarse particles diet,respectively.The diets were fed to tilapia with an initial body weight of 15.0 ± 0.5 g for 60 days.The weight gain,apparent digestibility coefficient of dry matter and crude protein(ADC of DM and CP)intestine evacuation velocity,protease and amylase activity trended to decrease and floating feces ratio increase with the increasing cork level from 2% to 4%in diets,and the WG of 3%,4% coarse groups and 4% fine group were8.81%,10.17% and 8.19% lower(P<0.05),and FCR was higher(P<0.05)than the control.At the same supplementation level,coarse particles groups had significantly higher floating feces ratio than fine particles groups.Villus height,muscular thickness and villus cross sectional area decreased with the increasing cork levels.The supplementation of protease in 4%coarse diet had higher WG(+7.2%),DM ADC,intestinal digestive enzyme activity,villus height,muscular thickness and villus cross sectional area(P<0.05),and lower FCR(-0.08)(P<0.10)than the 4% coarse diet.The supplementation of guar gum in 4% coarse diet significantly improved floating feces ratio(P<0.05).In conclusion,the floating feces ratio increased with increasing cork levels from 2% to 4%.The coarse particles produced more floating feces than fine particles,but showed more negative effect on the growth performance and intestinal histology.Dietary protease(175 mg/kg)could improve intestinal histology and growth performance,and the supplementation of guar gum(3 g/kg)could increase the floating feces ratio. |
