Animal Production Research, MTT Agrifood Research Finland, FI-31600, Jokioinen, Finland.
J Dairy Sci. 2013 Jan;96(1):440-50. doi: 10.3168/jds.2012-5642. Epub 2012 Nov 3.
Accurate quantitative information on the fate of dietary protein in the rumen is central to modern metabolizable protein systems developed to improve the efficiency of nitrogen utilization in ruminants. An in vitro method was developed to estimate the rate of soluble rapeseed meal (Brassica rapa L.) protein (SRMP) degradation. Unlabeled and (15)N-labeled solvent-extracted rapeseed meal were incubated alone or as an equal mixture (125 mg of N/L) with buffered rumen contents and a mixture of carbohydrates formulated to provide a constant source of fermentable energy during the course of all incubations. Incubations were made over 0.33, 0.67, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 6.0, 8.0, and 10.0 h. Enrichment of (14)N and (15)N isotopes in total N of ammonia (AN), soluble nonammonia (SNAN), and insoluble (ISN) fractions liberated during incubations with test proteins was determined. A model with 4 pools that accounted for both intracellular and extracellular N transformations was used to estimate the rate of SRMP degradation. Parameter values used in the model were adjusted based on the size of A(14)N, A(15)N, SNA(14)N, SNA(15)N, IS(14)N, and IS(15)N pools, measured at different time points during incubations with buffered rumen fluid. The mean rate of N degradation for SRMP was estimated at 0.126 (SD 0.0499) h(-1). No substantive difference in the rate of protein degradation or microbial protein synthesis was observed during incubations of labeled and unlabeled substrates with rumen fluid. In conclusion, combined use of data from incubations of unlabeled and (15)N-labeled rapeseed protein with buffered rumen inoculum provided sufficient information to allow for estimation of parameter values in a complex dynamic model of soluble protein degradation. Results indicate the potential of the technique to evaluate the degradability of SNAN of other dietary protein sources and implicate ruminal escape of soluble rapeseed protein as an important source of amino acids in ruminants.
准确的定量信息关于饮食蛋白质的命运在反刍动物瘤胃是中央的对现代可代谢蛋白质系统开发改进氮气运用效率。 一种体外方法被开发估计可溶解的油菜籽粉(甘蓝型油菜 L.) 蛋白质(SRMP)退化的率。 未被标记的和(15)N 被标记的被溶解的菜籽油粕被孵化了单独或作为一个相等的混合物(125 毫克的 N/L) 与被缓冲的瘤胃内容物和混合物被公式化的碳水化合物提供一个恒定的可发酵的能量来源在孵育的整个过程中。 孵育被做了在 0.33, 0.67, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 6.0, 8.0, 和 10.0 h。 丰富(14)N 和(15)N 同位素在氨(AN)的总 N，可溶解的非氨( SNAN)，和不能溶解的(ISN)分数在孵育期间被解放与试验蛋白质被确定了。 一个模型与占细胞内和细胞外的 N 变革的 4 个水池一起使用估计 SRMP 退化的率。 用于模型的参量价值根据 A(14)N， A(15)N， SNA(14)N， SNA(15)N， IS(14)N， 和 IS(15)N 水池的大小调整了，被测量在孵育的不同的时间点期间与被缓冲的瘤胃流体。 估计的 SRMP 的 N 退化的卑鄙率是 0.126 (SD 0.0499) h(-1)。 在孵育期间没有在退化率或微生物蛋白质综合上的坚固区别观察了在未被标记的和被标记的基质的用途与瘤胃流体。 总之，对无标记的和(15)N 被标记的菜籽油粕的孵育的数据的联合用途与被缓冲的瘤胃接种物提供了充足的信息考虑到参量价值的估计在一个复杂的动态模型可溶解蛋白质退化。 结果表明技术的潜力评估SNAN 的可降解性其他饮食蛋白质来源和牵连可溶解的菜籽油粕的反刍动物的逃跑作为氨基酸的一个重要来源。
