Comparitive Study On Channel Catfish And Grass Carp Fed Extruded Feed And Pelleted Feed With Differing Feeding Rates

Exp.1 Effects of different feeding rates of extruded and pelleted feeds on growth,nutrient retention and serum biochemical indices in channel catfish(Ictalurus Punctatus)The present study was conducted to investigate the effects of different feeding rates of extruded and pelleted feeds on growth,nutrient retention and serum biochemical indices in channel catfish.The two feeds were designed with the same formula(containing 30.8% crude protein and 5.3% crude lipid),and were fed to eight treatments of fish(pelleted feed with a satiation of 100%,90%,80%,70% and extruded feed with a satiation of 100%,90%,80%,70%)with triplicate cage per treatment(20 fish per cage)for 10 weeks.The results indicated that weight gain(WG)of the eight groups were 371.1%,328.1%,302.1%,281.1% and 370.5%,334.0%,311.0%,285.3%,respectively;the feed conversion ratio(FCR)of the eight groups were 1.43,1.46,1.41,1.32 and 1.44,1.43,1.37,1.30,respectively.Channel catfish fed extruded and pelleted feeds showed no significant difference in feed intake.The fish fed extruded and pelleted feed with the same feeding rate showed no significant differences in growth performance,whole-body composition and nutrient retention(P>0.05).In both extruded and pelleted feeds,weight gain(WG),feed conversion ratio(FCR),intraperitoneal fat ratio(IFR),whole-body lipid content,lipid retention(LR)and serum triglyceride(TG)content significantly decreased(P<0.05),while protein retention(PR)increased from 35.9% to 39.7% in extruded feeds and from 35.3% to 39.4% in pelleted feeds with the decrease of feeding rate from satiation(100%)to 70% of satiation(P<0.05).The condition factor(CF)and serum glucose(Glu)content showed no significant difference in extruded feeds(P>0.05),but the two indicators tended to decrease as feeding rate decreased in pelleted feeds(P<0.05).The above results demonstrated that channel catfish fed extruded feed had the similar growth to that fed pelleted feed with the same formula.Channel catfish fed pelleted and extruded feeds showed no significant difference in feed intake.The utilization of protein and feed could be improved by the reduced feeding rate from 100% to 70% of satiation.Exp.2 Effects of different feeding rates of extruded and pelleted feeds on growth,nutrient retention and digestive enzymes activities in grass carp(Ctenopharyngodon idellus)The present study was conducted to investigate the effects of different feeding rates of extruded and pelleted feeds on growth,nutrient retention and digestive enzymes activities in grass carp.The two feeds were designed with the same formula without fish meal inclusion(containing 30.3% crude protein and 3.6% crude lipid),and were fed to eight treatments of fish(pelleted feed and extruded feed with a satiation of 100%,90%,80% and 70%,respectively)with triplicate cage per treatment(15 fish per cage)for 10 weeks.The results indicated that weight gain(WG)of the eight groups were 423.4%,376.2%,344.5%,288.8% in extruded groups and 455.0%,409.3%,365.7%,311.4% in pelleted groups,respectively;the feed conversion ratio(FCR)of the eight groups were 1.51,1.50,1.48,1.54 and 1.41,1.40,1.39,1.43,respectively.Grass carp fed pelleted and extruded feeds showed no significant difference in feed intake(P>0.05).At the same feeding rate,fish fed extrude feed showed higher WG,protein retention(PR),lipid retention(LR)and lower FCR than those of fish fed pelleted feed(P<0.05).In both pelleted and extruded feeds,WG,intraperitoneal fat ratio(IFR),LR kept decreasing,but FCR decreased firstly,and then increased with the decrease of feeding rate(P<0.05).The group of 80% satiation showed the lowest FCR and the highest PR in both extruded and pelleted feeds.In the composition of whole-body and liver,crude lipid content decreased as the feeding rate decreased(P<0.05),but there was no significant differences in crude protein content among all treatments(P>0.05).Lipase activity in foregut tended to increase,but protease and amylase activities increased firstly,then decreased with the decrease of feeding rate(P<0.05).The above results indicated that grass carp fed extruded feed had higher values of WG and nutrient retention than those of fish fed pelleted feed with the same fish meal-free formula.There was no significant difference in feed intake between pelleted and extruded feeds,and grass carp showed the highest feed utilization at the feeding rate of 80% satiation in both extruded and pelleted feeds.Exp.3 Comparitive study on extruded and pelleted feeds of grass carp(Ctenopharyngodon idellus)with or without fish meal inclusionThe present study was conducted to investigate the effects of extruded and pelleted feeds with or without fish meal inclusion on the growth,nutrient retention and digestive enzymes activities of grass carp(Ctenopharyngodon idellus).Two feeds,a fish meal included feed(containing 2% fish meal)and fish meal free feed(fish meal was totally substituted by soybean meal),were designed and processed with pelleting and extruding,respectively.A total of four treatments were designed with fish meal free pelleted feed,fish meal free extruded feed,fish meal included pelleted feed and fish meal included extruded feed.The four feeds were fed to grass carp with an initial weight of 47.0±0.2 g for 10 weeks.In fish meal free feeds,the weight gain(WG)of fish fed extruded feed was increased by 7.46% and feed conversion ratio(FCR)was decreased by 0.11,when compared with the fish fed pelleted feed(P<0.05).In fish meal included feeds,fish fed extruded feed had similar WG and FCR to the fish fed pelleted feed(P>0.05).In pelleted feeds,the fish fed fish meal included feed had significantly higher WG(+4.18%),protein efficiency ratio(PER),protein retention(PR),lipid retention(LR)and lower FCR(-0.06)than the fish fed fish meal free feed(P<0.05);In extruded feeds,there was no significant difference in WG,FCR,PER and PR between fish meal included feed and fish meal free feed(P>0.05),but the former had a significantly higher LR than the latter(P<0.05).In both pelleted and extruded feeds,the activity of amylase in foregut of fish fed fish meal included feed was significantly higher than that of fish fed fish meal free feed(P<0.05);In pelleted feeds,the protease activity in foregut of fish fed fish meal included feed was significantly higher than that of fish fed fish meal free feed(P<0.05),but there was no significant difference in protease activity between the two extruded feeds(P>0.05).The activity of lipase in foregut showed no significant differences among all the treatments(P>0.05).The above results indicated that grass carp fed extruded feed had higher WG and better feed utilization than the fish fed pelleted feed without dietary inclusion of fish meal.With the inclusion of 2% fish meal in diet,grass carp fed the extruded feed or pelleted feed,present the similar WG and feed utilization.The inclusion of 2% fish meal in pelleted feed,but not in extruded feed,could improve the growth performance of grass carp.