Beijing Key Laboratory for Dairy Cow Nutrition, College of Animal Science and Technology, Beijing University of Agriculture, Beijing, China.
Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China.
J Anim Physiol Anim Nutr (Berl). 2018 Apr;102(2):421-428. doi: 10.1111/jpn.12749. Epub 2017 Jun 13.
This study was conducted to evaluate the effects of replacing alfalfa hay with rice straw (RS) or corn stover (CS) on amino acid (AA) profiles of gastrointestinal digesta in lactating cows. Eighteen lactating dairy cows were randomly assigned to one of three groups (n = 6) and fed identical concentrate and corn silage with different forages on dry matter basis: (i) 23% alfalfa hay and 7% Chinese wild rye hay (AH); (ii) 30% CS; and (iii) 30% RS. After the 14-week feeding, a total of 18 cows were slaughtered to collect digesta from four representative organs, including rumen, omasum, duodenum and jejunum. The AA profiles of ruminal microbial fraction were similar among the treatments, except for greater Arg in cows fed RS than in cows fed AH or CS. Most of the analysed AA changed under different diets. Significant differences were found among the microbial fraction, rumen fluid and rumen digesta, with greater essential AA in digesta than in microbial fraction or rumen fluid and greater essential AA in microbial fraction than rumen fluid. Significant differences in individual AA profiles of digesta and relevant fluid were found across the four representative digestive tract parts, including rumen, omasum, duodenum and jejunum, showing much lower Leu proportion in CS and RS than in AH in duodenal fluid. In summary, ruminal microbes may prefer using essential AA, rather than non-essential AA. The AA profile of ruminal microbes was constant except for Arg. The AA composition of digesta across the four digestive tracts changed dramatically, which indicated differences in the ability and efficiency of AA absorption. The lower duodenum absorbable Leu proportion in cows fed CS or RS indicated the shortage of Leu in CS or RS diets, which might also restrict the balanced AA absorption.
本研究旨在评估用稻草（RS）或玉米秸秆（CS）替代紫花苜蓿干草对泌乳奶牛胃肠道消化液氨基酸（AA）谱的影响。18 头泌乳奶牛随机分为 3 组（每组 6 头），根据干物质基础，用相同的精料和玉米青贮料喂养不同的饲草：（i）23%紫花苜蓿干草和 7%中国野生黑麦草（AH）；（ii）30% CS；和（iii）30% RS。在 14 周的饲养后，共有 18 头牛被屠宰，以收集来自四个代表性器官（瘤胃、网胃、十二指肠和空肠）的消化液。除了 RS 组奶牛的 Arg 高于 AH 组或 CS 组外，瘤胃微生物区系的 AA 谱在处理间相似。在不同的日粮下，大多数分析的 AA 发生了变化。在微生物区系、瘤胃液和瘤胃消化液之间发现了显著差异，消化液中的必需 AA 多于微生物区系或瘤胃液，微生物区系中的必需 AA 多于瘤胃液。在四个代表性的消化道部位（瘤胃、网胃、十二指肠和空肠）的消化液和相关液体的 AA 谱中发现了显著差异，在十二指肠液中，CS 和 RS 组的 Leu 比例明显低于 AH 组。总之，瘤胃微生物可能更喜欢使用必需 AA，而不是非必需 AA。除了 Arg，瘤胃微生物的 AA 谱是恒定的。四个消化道的消化液 AA 组成发生了显著变化，这表明 AA 吸收的能力和效率存在差异。CS 或 RS 组奶牛十二指肠可吸收 Leu 比例较低，表明 CS 或 RS 日粮中 Leu 不足，这也可能限制 AA 的平衡吸收。
