肉羊精料可代谢蛋白质预测模型的建立

目的 在通过概略养分或可消化养分建立肉用绵羊常用精饲料可代谢蛋白质（metabolic protein, MP）的预测模型,为动物日粮的科学配置提供依据。方法 试验选用14月龄,平均体重为（49.27±3.12）kg的安装有永久性瘤胃瘘管的杜寒杂交1代肉用羯羊6只,采用尼龙袋法和改进三步体外法测定10种精饲料的瘤胃有效降解率、瘤胃非降解蛋白质（undegraded dietary protein, UDP）及UDP小肠消化率;另外选用10只体况健康、平均体重（47.43±4.41）kg的杜寒杂交成年公羊分11期进行消化代谢试验,设11个处理组,其中1个基础饲粮组和10个试验饲粮组,试验组饲粮分别由高粱、玉米、大麦、小麦、燕麦、菜籽粕、花生粕、棉籽粕、豆粕及玉米酒糟（distillers dried grains with solubles, DDGS）等替换基础饲粮中羊 草、玉米和豆粕,每个处理10个重复,每个重复1只羊,每期饲喂20 d,其中预试期15 d,正试期5 d。试验羊提前打好耳号,使用伊维菌素进行驱虫,单栏饲养。由于各组饲粮营养成分存在差异造成采食量不同,在预饲期观察并确定最低组的采食量作为限喂量,每天饲喂两次,分别于8:00、16:30饲喂,每次饲喂600 g,自由饮水。采用全收粪尿法测定养分表观消化率和尿嘌呤衍生物法（purine derivative,PD）测定微生物合成蛋白质（microbial synthetic protein, MCP）,通过养分含量或可消化养分建立MP的预测模型。试验数据采用SAS 9.1中的NLIN程序计算a、b、c值和直线回归与多元回归程序分析建立MP估测模型,单因素方差分析（one-way ANOVA, LSD）进行显著性检验结果 饲料的粗蛋白质（CP）瘤胃降解率和UDP小肠消化率均因饲料种类不同而异,高蛋白饲料的CP瘤胃降解率和UDP小肠消化率较高,10种精饲料的CP瘤胃有效降解率的范围在43.71%—60.87%之间,UDP小肠消化率的范围在80.10%—92.86%之间,其中燕麦饲料的瘤胃有效降解率显著高于其他9种饲料 (P＜0.001),而其UDP小肠消化率显著低于其他9种饲料 (P＜0.001);饲粮组成不同,各营养物质的表观消化率不同;瘤胃可降解蛋白质与瘤胃非降解蛋白质比例的变化,不会对全消化道养分的表观消化率产生显著影响;本研究中10种饲料的MP与DP的比例范围在50.96%—62.33%之间,基于饲粮CP（%）含量预测可消化蛋白质（DP,%）的模型是DP=0.895×CP-2.663（R ²=0.994,n=10,P＜0.001）;基于养分含量（%）和可消化养分（%）建立的MP（g·kg ^-1 DM）预测模型分别是：MP=5.323×CP-14.374 (R ²=0.994,n=10,P＜0.001)和MP=5.899×DP+2.077 (R ²=0.984,n=10,P＜0.001)。 结论 饲粮中的粗蛋白质含量与可消化蛋白质存在强相关性;饲粮中概略养分含量和可消化养分与MP存在相关性,可以通过饲粮概略养分含量或可消化养分比较准确地估测精饲料的MP值。

Establishment of a Prediction Model of Metabolizable Protein of Concentrate for Mutton Sheep

【Objective】 The aim of this study was to establish a predictive model of metabolizable protein (MP) of concentrates, which is commonly used in feedstuffs of sheep by nutrient or nutrient digestibility. 【Method】 Six 14-month-old Dorper (♂) × thin-tailed Han sheep (♀) sheep with an average body weight of (49.27±3.12) kg fitted with a permanent rumen fistula were selected and used in testing effective degradation rate, rumen undegraded dietary protein (UDP) and intestinal digestibility of UDP by nylon bag method and three-step modified in vitro method. Ten healthy Dorper × thin-tailed Han ram with an average body weight of（47.43±4.41）kg were selected and used in 11 treatment groups including one basic diet group and 10 experimental groups（The Chinese wildrye hay, corn and soybean meal of basic diet were replaced by sorghum, corn, barley, wheat, oat, rapeseed peanut, cottonseed, soybean and DDGS.), respectively. Each period lasted for 20 d (15 d for adaptation and 5 d for trial period). The experimental sheep were prefixed with ear numbers, dewormed with ivermectin, and feed a single column. Due to the differences in the nutrient composition of each group of feeding foods, the amount of feeding in the lowest group was observed and determined during the adaptation as the limit of feeding, fed twice a day, at 8:00 and 16:30, respectively. Feed 600 g, free drinking water. Each ram is a replicate and all rams were used to determine the apparent digestibility of nutrients and microbial synthetic protein (MCP) using the urinary purine derivative method. The MP predictive model was established using proximal analysis of nutrient contents or nutrient digestibility. Using NLIN program in SAS 9.1 to calculate a, b, c values and linear regression and multivariate regression program analysis, MP estimation model was established, and the single factor variance analysis(one-way ANOVA, LSD) was significantly tested. 【Result】 The results showed that the rumen digestibility and digestion rate of CP in different concentrates were different, and CP degradability and intestinal digestibility of UDP of high protein diet were higher. The effective degradation rate of CP rumen in 10 kinds of feed ranged from 43.71% to 60.87%, and intestinal digestibility of UDP ranged from 80.10% to 92.86%. The effective degradation rate of rumen in oat feed was significantly higher than that of other feeds (P＜0.001), while intestinal digestibility of UDP was significantly lower than that of other feeds (P＜0.001). The diets had different composition and apparent digestibility of different nutrients. The digestion and absorption sites of dietary protein did not affect the apparent digestibility of nutrients. The ratio of MP to DP of 10 feeds in this study ranged from 50.96% to 62.33%, The digestible protein (DP, %) prediction model established by dietary CP (%) content was：DP=0.895×CP-2.663 (R ²=0.994, n=10, P＜0.001); The MP (g·kg ^-1 DM) prediction model established by nutrient contents (%) and apparent nutrient digestibility (%) were: MP=5.323×CP-14.374 (R ²=0.994, n=10, P＜0.001) and MP=5.899×DP+2.077 (R ²=0.984, n=10, P＜0.001).【Conclusion】Digestible protein had a strong relationship with crude protein in diet. The nutrient content and nutrient digestibility in diets were correlated with the presence of MP, and the MP values of concentrate feed could be estimated more accurately by the nutrient and nutrient digestibility in diets.