肉牛常用蛋白质饲料的饲用价值评价及粗蛋白质有效降解率预测模型建立

Evaluation on Feeding Value and Establishing Prediction Model of Effective Degradability of Crude Protein of Commonly-Used Protein Feedstuffs for Beef Cattle

本试验旨在通过体外产气法和尼龙袋法对6种肉牛常用蛋白质饲料的饲用价值进行评定,探究体外产气量参数和发酵参数与粗蛋白质有效降解率(EDCP)之间的关系,并利用体外产气法建立饲料中EDCP的预测模型,为丰富我国蛋白质饲料营养价值数据库提供数据基础。试验利用体外产气法测定了棉籽粕、菜籽粕、豆粕、向日葵粕、啤酒糟和干酒糟及其可溶物(DDGS)的72 h动态产气量和体外发酵参数,并计算产气量参数;利用尼龙袋法测定了上述6种蛋白质饲料的蛋白质降解率,计算降解参数。结果表明:1)豆粕的产气量显著高于其他蛋白质饲料(P<0.05)。2)豆粕的24 h体外发酵液的总挥发性脂肪酸(TVFA)含量最高,氨态氮(NH_(3)-N)含量与向日葵粕相似(P>0.05);向日葵粕的24 h体外发酵液的pH显著高于其他蛋白质饲料(P<0.05)。3)向日葵粕的72 h蛋白质降解率及EDCP最高。4)EDCP与体外产气量参数相关关系不显著(P>0.05),但与发酵液pH和NH_(3)-N含量呈显著正相关(P<0.05),与乙酸含量和乙酸/丙酸值呈显著负相关(P<0.05)。5)采用pH、酸性洗涤纤维(ADF)含量和24 h产气量(GP_(24 h))作为预测因子预测EDCP,决定系数(R^(2))达到0.998(P<0.05),预测方程为:EDCP=-833.690+138.088pH-1.219ADF-0.689GP_(24 h)。由此可见,不同饲料之间的体外发酵和瘤胃降解特性差异较大,豆粕的体外发酵指标高于其他饲料,向日葵粕的EDCP高于其他饲料;在正常的pH范围内,采用pH、ADF含量和GP_(24 h)能准确预测EDCP。

The purpose of this experiment was to evaluate the feeding value of 6 common protein feedstuffs for beef cattle by in vitro gas production method and nylon bag method,explore the relationship between in vitro gas production parameters and fermentation parameters and the effective degradability of crude protein(EDCP),and establish the prediction model of EDCP in feedstuff by using in vitro gas production method,which provided the data base for enriching the nutrient value database of protein feedstuff in China.The 72 h dynamic gas production and in vitro fermentation parameters of cotton seed meal,rapeseed meal,soybean meal,sunflower meal,beer grains and distiller’s dried grains with solubles(DDGS)were determined by in vitro gas production method,and the gas production parameters were calculated.The protein degradability of the 6 protein feedstuffs were determined by nylon bag method,and the degradation parameters were calculated.The results showed as follows:1)the gas production of soybean meal was significantly higher than that of the other protein feedstuffs(P<0.05).2)The 24 h total volatile fatty acid(TVFA)content in in vitro fermentation broth of soybean meal was the highest,and the ammonia nitrogen(NH_(3)-N)content was similar to that of sunflower meal(P>0.05).The 24 h pH in in vitro fermentation broth of sunflower meal was significantly higher than that of the other protein feedstuffs(P<0.05).3)The 72 h protein degradation rate and EDCP of sunflower meal were the highest.4)The EDCP was not significantly related to in vitro gas production parameters(P>0.05),but it was positively correlated with pH and NH_(3)-N content in fermentation broth(P<0.05),and negatively correlated with acetic acid content and acetic acid to propionate ratio(P<0.05).5)The determination coefficient(R^(2))of EDCP reached 0.998(P<0.05)by using pH,acid detergent fiber(ADF)content and 24 h gas production(GP_(24 h))as predictors,and the prediction equation was EDCP=-833.690+138.088pH-1.219ADF-0.689GP_(24 h).It is concluded that the in vitro fermentation and rumen degradation characteristics of different feedstuffs are various,the fermentation indices of soybean meal and the EDCP of sunflower meal are higher than that of other feedstuffs;within the normal pH range,EDCP can be accurately predicted by pH,ADF content and GP 24 h.