Tian Yujia, Zhang Xuewei, Huang Rongcai, Yu Peiqiang
Department of Animal Science, College of Animal Science and Veterinary Medicine, Tianjin Agricultural University, Tianjin 300384, China.
State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
Asian-Australas J Anim Sci. 2019 Feb 7;32(9):1381-1388. doi: 10.5713/ajas.18.0829. Print 2019 Sep.
The aims of this study were to reveal the magnitude of the differences in protein structures at a cellular level as well as protein utilization and availability among soybean meal (SBM), canola meal (CM), and rapeseed meal (RSM) as feedstocks in China.
Experiments were designed to compare the three different types of feedstocks in terms of: 1) protein chemical profiles; 2) protein fractions partitioned according to Cornell Net Carbohydrate and Protein System; 3) protein molecular structures and protein second structures; 4) special protein compounds-amino acid (AA); 5) total digestible protein and energy values; 6) in situ rumen protein degradability and intestinal digestibility. The protein second structures were measured using FT/IR molecular spectroscopy technique. A summary chemical approach in NRC model was applied to analyze truly digestible protein.
The results showed significant differences in both protein nutritional profiles and protein structure parameters in terms of α-helix, β-sheet spectral intensity and their ratio, and amide I, amide II spectral intensity and their ratio among SBM, CM and RSM. SBM had higher crude protein (CP) and AA content than CM and RSM. For dry matter (DM), SBM and CM had a higher DM content compared with RSM (P < 0.05), whereas no statistical significance was found between SBM and CM (P = 0.28). Effective degradability of CP and DM did not demonstrate significant differences among the three groups (P > 0.05). Intestinal digestibility of rumen undegradable protein measured by three-step in vitro method showed that there was significant difference (P = 0.05) among SBM, CM and RSM, which SBM was the highest and RSM was the lowest with CM in between. NRC modeling results showed that digestible CP content in SBM was significantly higher than that of CM and RSM (P < 0.05).
This study suggested that SBM and CM contained similar protein value and availability for dairy cattle, while RSM had the lowest protein quality and utilization.
本研究旨在揭示在中国作为饲料原料的豆粕（SBM）、菜籽粕（CM）和油菜籽粕（RSM）在细胞水平上蛋白质结构差异的程度以及蛋白质利用率和可利用性。
设计实验以比较三种不同类型的饲料原料在以下方面：1）蛋白质化学特征；2）根据康奈尔净碳水化合物和蛋白质系统划分的蛋白质组分；3）蛋白质分子结构和蛋白质二级结构；4）特殊蛋白质化合物——氨基酸（AA）；5）总可消化蛋白质和能量值；6）瘤胃原位蛋白质降解率和肠道消化率。使用傅里叶变换红外（FT/IR）分子光谱技术测量蛋白质二级结构。应用NRC模型中的综合化学方法分析真可消化蛋白质。
结果表明，在α-螺旋、β-折叠光谱强度及其比值以及酰胺I、酰胺II光谱强度及其比值方面，SBM、CM和RSM在蛋白质营养特征和蛋白质结构参数上均存在显著差异。SBM的粗蛋白（CP）和AA含量高于CM和RSM。对于干物质（DM），SBM和CM的DM含量高于RSM（P < 0.05），而SBM和CM之间未发现统计学差异（P = 0.28）。三组之间CP和DM的有效降解率未显示出显著差异（P > 0.05）。通过三步体外法测定的瘤胃未降解蛋白质的肠道消化率表明，SBM、CM和RSM之间存在显著差异（P = 0.05），其中SBM最高，RSM最低，CM介于两者之间。NRC模型结果表明，SBM中可消化CP含量显著高于CM和RSM（P < 0.05）。
本研究表明，SBM和CM对奶牛的蛋白质价值和可利用性相似，而RSM的蛋白质质量和利用率最低。
