Effects Of Protease,organic Acids (salts) On Growth,digestive Enzyme Activity And Apparent Digestibility Of Tilapia Oreochromis Niloticus×O.aureus And White Shrimp Litopenaeus Vannamei

Exp.1 Effects of Organic acid salts,protease and their combination in fish meal free diets on growth,digestibility and intestinal tissue structure of tilapia(Oreochromis niloticus × O.aureus)The present study was conducted to evaluate the effects of organic acid salts blend(OAB),protease-complex(Pr),and their combination(OAB+Pr)in fish meal free diets on growth,nutrient retention and digestibility of tilapia.Five diets were designed: a positive control(PC)diet containing 8% fish meal(FM),a negative control(NC)diet containing 0% FM and 10.4% meat and bone meal,and three other diets supplemented with OAB(922 mg/kg),Pr(175 mg/kg)and OAB+Pr(922mg/kg+175 mg/kg)to the NC diet.Tilapia with an initial body weight of 7.0 ± 0.2 g were fed the five diets for 9 weeks.The results showed that the growth performance,nutrient digestibility and retention of NC group had the lowest values among groups.Weight gain of fish fed the OAB and OAB+Pr diets were higher,and feed conversion ratio were lower(P<0.05)compared to those fed the NC diet,while no differences with those fed the PC diet.The digestibility of dry matter,crude protein,minerals and protein retention were improved in fish fed the OAB+Pr diet(P<0.05),but not in those fed OAB or Pr diet(P>0.05).There were no differences in whole body composition and lipid retention among the treatments(P>0.05).The supplementation of OAB and Pr alone or combined,significantly increased the villi height but not the width when compared to the NC group.It can be concluded that dietary supplementation of OAB+Pr in a fish meal free diet improves growth and nutrient digestibility in tilapia compared to those fed the fish meal free diet.Exp.2 Effects of partial replacement of fish meal with meat and bone meal by organic acids(salt)on growth,hepatopancreas and pancreatic digestive enzyme activity and apparent digestibility of white shrimp(Litopenaeus vannamei)The study was conducted to evaluate the effects of organic acid and protease in the diet where meat and bone meal partially replaces fish meal on growth,hepatopancreas digestive enzyme activity and apparent digestibility of white shrimp.The study used the diet containing 18% fish meal as positive control diet,and the diet containing 12% fish meal as negative control diet(6% fish meal was replaced by meat and bone meal,and microencapsulated lysine and microcapsule methionine to align it with the positive control group were added).Besides,2 g/kg citric acid,malic acid and sodium butyrate were supplemented in the negative control diet respectively.The white shrimp with an initial body weight of 4.6±0.05 g were fed the five groups of diets for 9 weeks.The results showed that the weight gain rate decreased by 11.4%(P<0.05)after the replacement of fish meal with meat and bone meal,the feed conversion ratio was increased by 0.19(P<0.05),and the dry matter digestibility was reduced by 10.31% and crude protein digestibility was decreased by 5.48%(P<0.05).The weight gain rates after the supplementation of citric acid and sodium butyrate increased by 7.47% and 6.49% respectively(P<0.05),the feed conversion ratio decreased by 0.15 and 0.11(P<0.05),and the digestive enzyme activity and apparent digestibility were only numerically improved that had no significant difference compared with the negative control group(P>0.05).What's more,the weight gain rate of the malic acid group increased by 1.7%(P>0.05),and the feed coefficient decreased by 0.07(P>0.05).In summary,after the partial replacement of fish meal with meat and bone meal,the diet where the 2g/kg citric acid and sodium butyrate were added significantly promoted the growth of white shrimp and improved the digestive enzyme activity and the apparent digestibility of nutrients.However,adding malic acid had no significant effect on growth,digestive enzyme activity and apparent digestibility of nutrients of white shrimp.Exp.3 Effects of partial replacement of fish meal with soybean meal by organic acids(salt)on growth,hepatopancreas and pancreatic digestive enzyme activity and apparent digestibility of white shrimp(Litopenaeus vannamei)The study was conducted to evaluate the effects of organic acid and protease in the diet where soybean meal partially replaces fish meal on growth,hepatopancreas digestive enzyme activity and apparent digestibility of white shrimp.The study used the diet containing 18% fish meal as positive control diet,and the diet containing 12%fish meal as negative control diet(6% fish meal was replaced by soybean meal,and microencapsulated lysine and microcapsule methionine to align it with the positive control group were added)was designed as the negative control diet.Besides,2 g/kg citric acid,malic acid and sodium butyrate were supplemented in the negative control diet respectively.The white shrimp with an initial body weight of 4.6 ± 0.05 g were fed the five groups of diets for 9 weeks.The results showed that the weight gain rate decreased by 10.59%(P<0.05)after the replacement of fish meal with soybean meal,the feed conversion ratio increased by 0.16(P<0.05),and the digestive enzyme activity and the apparent digestibility of nutrients only showed a numerical decrease(P>0.05).The weight gain rates after the supplementation of citric acid and sodium butyrate increased by 5.46% and 5.12% respectively(P<0.05),the feed conversion ratio decreased by 0.11 and 0.10(P<0.05),and the digestive enzyme activity and apparent digestibility were only numerically improved that had no significant difference compared with the negative control group(P>0.05).What's more,the weight gain rate of the malic acid group increased by 2.27%(P>0.05),and the feed coefficient decreased by 0.06(P>0.05).In summary,after the partial replacement of fish meal with soybean meal,the diet where the 2g/kg citric acid and sodium butyrate were added significantly promoted the growth of white shrimp and improved the digestive enzyme activity and the apparent digestibility of nutrients.However,adding malic acid had no significant effect on growth,digestive enzyme activity and apparent digestibility of nutrients of white shrimp.