淀粉预糊化对中华鳖生长和饲料利用的影响

Effects of starch pre-gelatinization on growth performance and feed utilization of Chinese soft-shelled turtle(Pelodiscus sinensis)

探讨生淀粉替代预糊化淀粉对中华鳖(Pelodiscus sinensis)生长和饲料利用的影响。试验设计了等氮、等能、等淀粉含量,不同生淀粉替代预糊化淀粉比率(0%、33%、67%和100%)的4种饲料,测定了各试验组稚鳖的摄食率、生长速度、消化率、体组成。结果显示,各试验组稚鳖的特定生长率、肝体指数、脏体指数、鳖体组成、饲料干物质、蛋白质和脂肪的消化率均无显著差异;随着生淀粉替代预糊化淀粉比率的增高,摄食率逐渐增加,蛋白质效率逐渐降低;生淀粉完全替代预糊化淀粉,饲料系数显著增高。研究结果表明,中华鳖对生淀粉具有较高的利用能力,饲料淀粉预糊化可以增加稚鳖的饲料利用率,但是对生长性能没有影响。

Carbohydrate is considered the least expensive form of dietary energy for animals.The ability of farmed fish to use dietary carbohydrates as an energy source is generally lower than that of terrestrial livestock.The relative efficiency of dietary carbohydrate utilization by fish has been associated with dietary carbohydrate level,molecular complexity and the technological treatments applied.Starch is the main source of dietary carbohydrate in aquafeed,and pre-gelatinization is a widely used method to improve the starch utilization.Many researches showed that gelatinized starch is more significant in carnivores to improve feed digestion and utilization.However,some experiments reported that total gelatinization of diet starch would not has positive effect on the growth of some fish.Chinese soft-shelled turtle（Pelodiscus sinensis）is carnivore,which was reported had low ability to use dietary carbohydrates.Pre-gelatinized starch is used universally in Chinese turtle diet now,but the ability to use raw starch is still unknown.This experiment was conducted to evaluate if starch pre-gelatinization could increase the growth and feed utilization of P.sinensis.Four test diets were designed with adding the same level of cassava starch（20%）,but different replacement ratio of pre-gelatinized starch by raw starch（0%,33%,67% and 100%）.Nutritional compositions of four test diets were similar,with about 46% protein,9% fat and 16kJ/g energy.The feeding experiment lasted for 7weeks.Chinese turtles with initial average body mass of 6.5g were fed twice a day at（30±1）℃.The feeding rate,specific growth rate,feed conversion ratio,protein efficiency ratio,viscera-somatic index,hepatosomatic index,nutrient digestibility,and body composition of turtle were analyzed.Differences in specific growth rate,viscera-somatic index,hepatosomatic index,digestibility of dry mass,protein and fat of Chinese turtle fed different diets were all insignificant（P 0.05）.However,starch pregelatinization affected feeding rate,feed conversion ratio and protein efficiency ratio.Feeding rate increased with the replacement ratio of pre-gelatinized starch by raw starch,and protein efficiency ratio decreased linearly.Feeding rate of turtle fed diet 1was significantly higher than those fed diet 3and 4.Protein efficiency ratio of turtle fed diet 1and2 were both significantly lower than those fed diet 3and 4,differences in protein efficiency ratio of the groups between diet 1and 2and between diet 3and 4were both insignificant.Feed conversion ratio increased significantly with the total replacement of pre-gelatinized starch by raw starch.Feed conversion ratio of turtle fed diet 1and 2were both significantly higher than those fed diet 3and 4.Contents of body water,protein,fat,ash and energy of turtle fed different diets were all different insignificantly.Those results indicate that Chinese turtle has a good ability to use raw starch,and the growth performance of P.sinensis is not affected by starch pre-gelatinization,but feed utilization can be enhanced.Since the price of pregelatinized starch is higher than that of the raw starch,the raw cassava starch can be used and totally replace the pre-gelatinized cassava starch in the Chinese turtle diet.