Apparent Digestibility Of 17 Raw Materials By Largemouth Bass(Micropterus Salmoides)

The apparent digestibility of animal protein ingredients and plant protein ingredients based on extruded processing by largemouth bass were examined using ingredient substitution and yttrium oxide as the inert marker.The reference diet was mainly composed of Peru anchovy fishmeal as the only protein source and tapioca which only contains starch to avoid the interaction between different raw materials.Each raw material was tested at 30%inclusion and feces were collected using manual stripping method.The main results including two parts.Part 1: Animal protein ingredients included four sources of fishmeal(Peru anchovy fishmeal,China sardine fishmeal,China anchovy fishmeal,China mackerel fishmeal),four sources of poultry by-product(poultry by-product meal,poultry carcasses meal,hydrolyzed feather meal,spray-dried granulated inedible egg product)and two sources of potential alternative animal protein ingredients(defatted Tenebrio molitor larvae meal,hydrolysates of stickwater and soybean).The results indicated that ADCs of dry matter,energy and crude protein of animal protein ingredients by largemouth bass had great variability which ranged from 67.0%-96.4%,75.6%-98.6% and 72.0%-95.3%,respectively.The ADCs of spray-dried granulated inedible egg product was significantly higher than other animal ingredients,while hydrolyzed feather meal and defatted Tenebrio molitor larvae meal were significantly lower than all animal protein ingredients.The ADCs of four sources of fishmeal,poultry by-product meal,poultry carcasses meal and hydrolysates of stickwater and soybean were quite similar,which ranges from 77.4%-86.2%,81.8%-94.4% and 84.7%-88.9%,respectively.Digestibility of dry matter and energy were highly positively correlated(r=0.93).ADCs of amino acids reflected the crude protein digestibility of these raw materials and ranged from70.7%-94.9%.With the exception of China mackerel fishmeal and Peru anchovy fishmeal,other fishmeal and poultry by-product meal and poultry carcasses meal had no significant differences in ADCs of phosphorous,but all of them had lower digestibility of phosphorous(37.2%-61.7%).Part 2: Plant protein ingredients included soybean products(46%soybean meal,soy protein concentrate,fermented soybean meal TB,fermented soybean meal YH)and cottonseed products(cottonseed meal,degossypolled cottonseed protein TY,degossypolled cottonseed protein JL).The results indicated that the ADCs of dry matter and energy in plant protein ingredients by largemouth bass had a wide variability,which ranged from 55.0%-78.0% and 67.0%-84.8%,respectively.The ADCs of dry matter and energy of soybean protein concentrate and 46% soybean meal had no significant difference with Peru anchovy fishmeal,but the ADCs of dry matter and energy in other plant ingredients were significantly lower(P < 0.05).Digestibility of dry matter and energy were highly positively correlated(r=0.95).All plant proteins were well digested compared with Peru anchovy fishmeal,recording protein ADCs between 83.1%-96.5% and the soybean products had higher protein digestibility than fishmeal and cottonseed product.ADCs of amino acids of plant ingredients were highly consistent and reflected the crude protein ADCs of these raw materials(r=0.93).In conclusion,with the exception of hydrolyzed feather meal and defatted Tenebrio molitor larvae meal,largemouth bass were efficient at digesting nutrients and energy from animal protein ingredients,especially for spray-dried granulated inedible egg product.However,the use of phosphorous should be pay attention.As for the plant protein ingredients,the ADCs of dry matter and energy of soy protein concentrate and 46% soybean meal had no significant difference with Peru anchovy fishmeal while the ADCs of protein were higher.ADCs of other plant protein ingredients were significantly lower than Peru anchovy fishmeal.In addition,the same reference diet with a batch of fish were used in two experiments.Therefore,ANOVA was used to examine whether there was any difference between the respective ADCs of the reference diet in two experiments.The results showed there was no significant difference between two ADCs of reference diets.Hence,the ADCs of animal and plant protein ingredients were evaluated together.The results indicated that largemouth bass were more efficient at digesting animal protein ingredients than plant ingredients.Spraydried granulated inedible egg product had the highest ADCs among all ingredients which almost was complete digested.Poultry by-product meal,poultry carcasses meal,four sources of fishmeal,hydrolysates of stickwater and soybean,soy protein concentrate and 46%soybean meal also were well digested but were lower than spray-dried granulated inedible egg product.ADCs of crude protein and amino acids of hydrolyzed feather meal and defatted Tenebrio molitor larvae meal had no significant differences with soy protein concentrate and46% soybean meal,but ADCs of dry matter and energy was significantly lower(P< 0.05).While fermented soybean meal TB,fermented soybean meal YH,cottonseed meal,degossypolled cottonseed protein TY and degossypolled cottonseed protein JL were lowset at digestibility.The poor digestibility of hydrolyzed feather meal,defatted Tenebrio molitor larvae meal and plant protein ingredients excepted for soy protein concentrate and 46%soybean meal in this study indicated that these raw materials should not be used in a large proportion in largemouth bass diets.While four sources of fish meal,poultry by-product meal,poultry carcasses meal,spray-dried granulated inedible egg product,hydrolysates of stickwater and soybean,soy protein concentrate and 46% soybean meal can be used as efficient and high-quality protein ingredients for largemouth bass.