Effect of ration size and feeding frequency on growth,feed utilization,body composition and some haematological characteristics of juvenile snapper,Lutjanus johnii (Baloch,1792)

The effect of ration size and feeding frequency on growth rate,feed utilization efficiency,body composition and haematological characteristics of juvenile snapper,lutjanus johnii (body weight 27.1-140.0 g) were examined. fish were maintained in recirculating system (rearing tanks of 0.28 m3,water temperature 27°c) and fed with a test diet (protein 40%,lipid 18.4% and energy 321.0 kcal 100 g-1 dry diet) at six ration levels of 2.0,2.5,3.0,3.5,4.0 and 4.5% body weight per day (bw d-1) for four feeding frequencies per day. each ration level and feeding frequency was randomly assigned to three tanks of fish with 10 fish per tank for 75 days. significantly higher weight gain,specific growth rate and feed conversion efficiency were observed at ration level from 2.5 to 4.5% bw d-1 and feeding frequency of three to four times daily (p< 0.05). broken-line regression on weight gain yielded an estimated ration requirement of 2.45% bw (y = 0.52 - 0.007(r - xlr),r = 2.45 ± 0.33) with 2.9 times daily (y = 0.41 - 0.005(r - xlr),r = 2.99 ± 0.21). there were no significant (p>0.05) differences in protein efficiency and retention of protein and energy among treatments. digestibility of protein,lipid and energy was significantly (p<0.05) higher at 2.0 to 2.5% bw d-1 and three to four meals daily. the moisture,protein and ash contents of fish whole body,muscle,liver and viscera were not significantly (p>0.05) affected by either ration level or feeding frequency. the highest lipid contents of whole body,liver and viscera were observed in fish at ration levels from 2.5 to 4.5% bw d-1 and feeding frequency of three to four times daily. the muscle lipids decreased significantly (p<0.05) with increasing feeding frequency,whereas that of liver increased. the cholesterol level,plasma triglycerides and haematocrit values remained similar (p>0.05) among the fish fed on different ration level and feeding frequency. total plasma lipids of fish fed 2.5% bw d-1 showed the maximum level which statistically differed (p<0.05) only from that of fish fed 2.0% bw d-1 while total plasma lipids were similar in fish receiving one to four meals daily. the condition factor,viscerosomatic index,hepatosomatic index and mesenteric fat index were significantly (p< 0.05) higher in fish at ration levels from 2.5 to 4.5% bw d-1 and feeding frequency of three to four times daily. these results suggest that under similar culture conditions,the optimum ration level and feeding frequency of the juvenile snapper (from initial weight of 27.1 to 140.0 g) are 2.5% bw d-1 and three times daily,respectively. copyright 2015 zoological society of pakistan.