Effects Of Different Processing Techniques On Feed Quality,growth Performance And Apparent Digestibility Of GIFT Tilapia

In this experiment,GIFT Tilapia was used as the research object to investigate the effects of different processing technologies on feed quality and growth performance of GIFT tilapia.Three experiments were set up: 1.Effect of pelleting temperature on feed quality and growth of GIFT tilapia;2.Effect of particle size on growth performance,ADC,and intestinal development of GIFT tilapia;3.ADC of GIFT tilapia to nutrients in extruded diet and sinking diet under low temperature conditions.The main results are as follows:1.The experiment was conducted at five different temperatures of 70�C,85�C,100�C,115�C,and 130�C,to investigate the effects of pelleting temperature e on the feed quality and the growth performance of GIFT tilapia(9.95�0.10)g.The results showed: With the increase of pelleting temperature,the hardness increased first and then decreased significantly(P<0.05).The gelatinization degree of starch was firstly increased then remained basically stable.And first the rate of dissolution loss decreased significantly(P<0.05),then keep it steady.The water content of 115�C group feed was significantly lower than that of the first three groups(P<0.05);Crude fat and most amino acid contents increased with the reduce of pelleting temperature,but there was no significant difference in crude protein content between the treatments(P>0.05).The weight gain rate of tilapia in the 130�C group was significantly lower than that in the 70�C,85�C,and 100�C groups(P<0.05).The feed coefficient of the tilapia in the 70�C group was significantly higher than that in the other groups(P<0.05).There was no significant difference in ADC of crude protein and crude fat between the five feeds of GIFT tilapia(P>0.05);ADC of essential amino acids decreased with the increase of pelleting temperature,and the 115�C group was significance lower than the 70�C group(P<0.05).In addition,the pelleting temperature increased,and the enzymatic activity of white matter in the guts of each group of G.tilapia was not significantly different(P>0.05);the activity of amylase and lipase decreased with the increase of pelleting temperature,and the 130�C group was significantly lower.In the 70�C group(P<0.05).The suitable pelleting temperature should be controlled between 85-100�C2.This experiment used 0.4mm,0.8mm,1.0mm,1.2mm,and 1.5mm sieves to smash the raw materials,then made pellet feeds to study the effect of different smashing sieve aperture on the growth performance,apparent digestibility and intestinal tissue structure of GIFT Tilapia(10.21�0.11)g.The result were as follows: As the size of the sieve aperture increased,the weight gain rate of GIFT Tilapia was decreased,while the feed coefficient and feeding rate were also increased,and the 1.5mm group was significance higher than the three group of 0.4,0.8 with 1.0mm(P<0.05).The sieve aperture had no significant effect on the nutritional composition of whole fish and muscle(P>0.05).There was no significant difference in ADC,lipase and amylase activity of GIFT tilapia(P>0.05),while the protease activity of 0.4mm was significantly higher than that of the other four groups(P<0.05).The villus height of the intestine of the 0.4mm and 0.8mm groups is well developed.Considering the comprehensive production considerations,the sieve aperture of the GIFT tilapia feed should be between 0.8-1.0mm.3.The two diets(extruded diet who making at a high temperature(135-150?)and sinking diet who making at a low temperature(80-90?)were fed to GIFT tilapia under 22? and 28? temperatures,to compare ADC of GIFT tilapia(54.21�0.47)g to ingredient of these two diets.Compared with the temperature 28�C,the weight gain rate,specific growth rate and feed coefficient significantly(P<0.05)decreased and the feeding rate was significantly(P<0.05)increased;It also significantly reduced ADC of GIFT tilapia to dry matter,crude protein and crude fat of the two diets(P<0.05);and There was no significant difference in ADC of EAA and TAA(P>0.05).The weight gain rate,specific growth rate was no significant difference between feeding extruded diet and sinking diet(P>0.05);and ADC of GIFT tilapia to crude protein,amino acids(except Phe)of two diets were not significantly(P>0.05)difference under the condition of low temperature(22�C).However,compared with sinking diet,the feeding rate,feed coefficient significantly(P<0.05)decreased.And ADC of GIFT tilapia to crude fat of extruded diet was significantly higher than that of sinking diet(P<0.05).In conclusion,compared with feeding sinking diet,feeding extruded diet had no significant difference in the growth,ADC of dry matter and crude protein of GIFT tilapia.However,it could significantly improve feed efficiency and ADC of crude fat under low temperature.