Physical And Chemical Properties Of Different Processed Feedstuffs And Their Effects On Growth Performance

This study using the two factor interaction design, the crude protein content were 28% and 33%, processing was set to soft pellets, hard pellets and extruded pellets process. Fish meal and casein were used as dietary protein sources to produce the extruded feeds, pelleted feeds and soft pellet feeds at two protein levels( 28% and 33%). Then, properties of these diets were measured. And a 60-day growth experiment was conducted in a recirculated filtered rearing system to research the effects of different produced feeds on growth performance, digestive enzyme activities and body composition of average intial body weight(16.24±0.03g) of Tilapia. The results were as follows:1.Under the same crude protein level of pellet,hardness of soft pellet was smallest of all pellets, hardness of hard pellet was biggest of all pellets,hardness of extruded pellet was between between that of hard pellet and soft pellet feed(P<0.05).2.Compared with the extruded feed, the expansion ration and gelatinization of soft pellet were lower than those of extruded pellet and hard pellet(P<0.05), the sinking speed was faster than that of extruded pellet and hard pellet( P<0.05), the leaching ratio was higher than those of extruded pellet and hard pellet(P<0.05);expansion ration, sinking speed, leaching ratio and gelatinization of hard pellet were all between those of soft pellet and extruded pellet.3.Growth experiment suggested that,the weight gain and specific growth rate of Tilapia in feeding soft pellet were significantly higher than Tilapia in feeding extruded pellet(P<0.05),those of hard pellet were between soft pellet and extruded pellet.These results suggested that different processing technology had a significantly effect on growth speed of Tilapia(P<0.05), and soft pellet was the best of all.4.Under 28% crude protein, feed conversion ratio of hard pellet was significantly low than that of extruded pellet(P<0.05); feed conversion ratio of soft pellet was between that of hard pellet and extruded pellet(P>0.05);protein efficiency rate of extruded pellet was significantly higher than that of hard pellet(P<0.05), protein efficiency rate of soft pellet was between that of hard pellet and extruded pellet, and had no significantly difference withhardpellet and extruded pellet(P>0.05).But under 33% crude protein, feed processing had no significantly effect on feed conversion ratio and protein efficiency rate(P>0.05). These results suggested that different processing technology had a significantly effect on feed conversion ratio and protein efficiency rate under low dietary protein level(P<0.05), and feed conversion ratio of hard pellet was the best of all. But under high dietary protein level,different processing technology had no significantly effect on feed conversion ratio and protein efficiency rate.5. Under 28% crude protein, dry matter apparent digestibility and crude protein apparent digestibility of hard pellet were significantly higher than those of soft pellet and extruded pellet(P<0.05); about lipid apparent digestibility of soft pellet was significantly higher than that of hard pellet(P<0.05); But under 33% crude protein, different processing technology had no significantly effect on nutrient apparent digestibility(P>0.05).These results suggested that different processing technology had a significantly effect on nutrient apparent digestibility under low dietary protein level(P<0.05), and hard pellet was the best of all.But under high dietary protein level, different processing technology had no significantly effect on nutrient apparent digestibility(P>0.05).6. Under 28% crude protein, intestinal mucosae activities of extruded pellet was significantly higher than hard pellet( P<0.05);Under 33% crude protein, amylase activities in hindgut and liver of extruded pellet were significantly higher than those of soft pellet(P<0.05).The above stated results suggested, different processing technology had a significantly effect on growth of Tilapia. Mainly considering the growth performance, it was concluded that suitable feed should be feed containing28% crude protein and extruded at room temperature.