影响鱼粉胃蛋白酶消化率的因素之探讨

鱼粉消化率是鱼粉含有可被动物体消化吸收的蛋白质含量的真实反映,是评价鱼粉质量的重要指标。本文讨论了原料鱼的新鲜度、鱼粉生产工艺、贮藏时间、脂肪含量、氨基酸组成等对鱼粉胃蛋白酶消化率的影响,并对本研究的进一步工作做了讨论。     

Evidence of genotype–diet interactions in the response of rainbow trout (Oncorhynchus mykiss) clones to a diet with or without fishmeal at early growth

This study examined the genetic variability and genotype × diet interactions during early growth (initial mean body weight 1.2 g) among seven heterozygous clones of rainbow trout, Oncorhynchus mykiss. The clones were hand-fed a diet containing either fishmeal or plant proteins during a 49-day trial divided into two periods (P1, 26 days, and P2, 23 days). Weight, variation of weight within clone, feed intake, feed efficiency and mortality were calculated for both periods.There was a highly significant effect of diet and of clone for all traits at both periods, except for feed efficiency and mortality at P1. Highly significant interactions between diet and clone were also recorded for all these traits, except for mortality at P1. The occurrence of genotype × diet interactions when feeding juvenile rainbow trout with an all plant-protein diet indicates that a highly performing genotype on a fishmeal diet may perform poorly when fed a plant-protein diet. Interactions were found for the two major determinants of growth, i.e. feed intake and feed efficiency, showing that the dietary response differs according to the genotype. Monitoring of the within-clone variability of weight showed that a plant-based diet is likely to enhance the overall phenotypic variance in a population, whatever its initial genetic variability.     

鱼粉的胃蛋白酶消化率及其影响因素的研究

利用胃蛋白酶法对国产鱼粉的消化率进行了测定，得出国产鱼粉特级品的消化率在90％以上，一级品在88％以上，二级品在85％以上。与进口鱼粉相比，国产鱼粉质量已有了很大提高，但还存在一定差距。另对鱼粉存放时间、VBN值、VA值对消化率的影响做了初步探讨。     

对几种鱼粉质量的检测与分析

为了解新疆部分地区鱼粉市场的质量情况，以自制鱼粉为参照，对4种市场销售的鱼粉进行了粗蛋白质、粗灰分、粗脂肪、粗纤维和钙、磷含量的分析。结果显示：所检验的4种鱼粉粗蛋自质含量均明显低于自制鱼粉和国家三级标准要求，最低者只达到26％左右；4种鱼粉的粗灰分含量均高于自制鱼粉，其中有2种鱼粉粗灰分含量高于国家三级标准，最高者达44％；一种鱼粉粗脂肪含量高于国家三级标准和自制鱼粉粗脂肪含量，达21％左右；检测鱼粉粗纤维含量均高于自制鱼粉，其中有3种粗纤维含量高于国家三级鱼粉标准。结论：①综合4种鱼粉的检测结果，判断这4种鱼粉均为劣质鱼粉。②对鱼粉进行定性判断时，鱼粉粗灰分含量和蛋白质含量指标具有较高的灵敏度。     

微波–干灰化混合消解和原子荧光光度法测定鱼粉中总砷

采用微波–干灰化混合消解法进行前处理,原子荧光光度法测定鱼粉中的总砷含量。结果显示,样品经微波消解、干灰化、原子荧光分光光度法分析,加标回收率为96.8%~103.6%,相对标准偏差为2.4%,检出限为0.1μg/L;采用CNAS能力验证鱼粉样品,微波–干灰化混合消解法总砷测定结果与中位值一致。研究表明,微波–干灰化混合消解法能减少前处理过程中砷(As)因高温或消解不完全导致的损失,使鱼粉中的各种形态的As完全转化为无机砷离子,方法重现性好、准确可靠,是测定鱼粉中的总砷含量理想的前处理方法,也可以用于砷形态比较复杂的食品、饲料等样品中总砷的测定。     

基于随机森林的鱼粉蛋白近红外定量分析

基于近红外(NIR)光谱技术,采用随机森林(RF)回归方法测定饲料鱼粉的蛋白含量。考虑到RF模型的随机性,通过调试决策树数量(ntree)和分裂变量数目(nsv)来进行模型优选;利用基尼系数(G)的下降量来判断近红外波长变量的建模重要性,进而为鱼粉蛋白的NIR分析优选信息波长,以提高NIR定量分析精度。根据统计学原理,选择具有较低计算复杂度的等效最优模型。优选的RF模型构建471个决策树,需要随机的103个波长变量进行树节点分裂,同时通过计算节点分裂前后G的平均下降量来选择52个近红外信息波长进行定标校正,得到等效最优的校正模型,校正均方根偏差和校正相关系数分别为3.970%和0.943;经过独立的预测集样品对最优RF模型进行检验,预测均方根偏差为5.271%,预测相关系数为0.906,说明RF回归结合G系数的波长优选能够有效地提高NIR光谱应用于鱼粉蛋白定量的预测能力。     

Replacement of Fishmeal by Single Cell Protein Derived from Yeast Grown on Date (Phoenix dactylifera) Industry Waste in the Diet of Nile Tilapia (Oreochromis niloticus) Fingerlings

Isonitrogenous and isocaloric diets (32% protein, 4.3 Kcal/g) were formulated to replace fishmeal by single cell protein (SCP) from two yeasts, Saccharomyces cerevisiae and Candida utilis, grown on date (Phoenix dactylifera) processing waste in diets for two size groups (avg 15.39 g and 25.14 g) of juvenile Nile tilapia (Oreochromis niloticus). A control diet (T₁) with fishmeal and six experimental diets (S1, S2, and S3 with S. cerevisiae, and C1, C2, and C3 with C. utilis) each containing 11.6%, 23.2%, and 34.2% yeast as SCP were prepared to replace 25%, 50%, and 75% of fishmeal, respectively. Tilapia fed on the control and experimental diets (S1, S2, C1, C2) with 25% and 50% replacement of fishmeal showed better growth and feed utilization. Fish fed on diets S3 and C3 (75% fishmeal replacement) had significantly (p < 0.05) poorer growth suggesting that yeast SCP can replace up to 50% of fishmeal in juvenile tilapia diets.     

蚕蛹在水产动物营养中的应用研究

随着水产养殖的集约化,作为传统蛋白源的鱼粉供应有限、价格高涨,使得我国优质蛋白源短缺问题日益突出,严重影响着我国水产养殖业的长远发展。我国是一个蚕桑大国,蚕蛹资源丰富,同时蚕蛹具有蛋白含量高、氨基酸平衡等优点,适宜作为水产饲料中鱼粉的优质替代物。目前已有少量研究关注蚕蛹在水产饲料中的应用,效果各不相同,具体机制有待研究,本文就其在水产饲料中的应用综述如下。     

鱼粉中氨基酸近红外光谱定量分析

收集了145个鱼粉样本,应用偏最小二乘（PLS）方法,建立了鱼粉中17种氨基酸和总氨基酸NIRS定标模型。天冬氨酸、蛋氨酸、赖氨酸、苏氨酸、谷氨酸、甘氨酸、丙氨酸、缬氨酸、异亮氨酸、亮氨酸、苯丙氨酸、精氨酸、脯氨酸和总氨基酸的化学分析值与NIRS预测值的决定系数R^2都达到0．87以上,相对标准差均小于10％,相对分析误差均大于3;酪氨酸的决定系数R^2为0．8678,相对标准差为8．65％,相对分析误差为2．77;组氨酸、丝氨酸和半胱氨酸的决定系数R。分别为0．9005、0．7436和0．3541,相对标准差分别为14．19％、17．85％和33．85％,相对分析误差分别为2．96、1．98和1．04。结果表明,利用近红外光谱分析技术能够较准确地检测鱼粉中14种氨基酸;酪氨酸只能进行粗略估测;组氨酸、丝氨酸和半胱氨酸难于进行实际检测。