College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, P.R. China.
College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, P.R. China.
J Dairy Sci. 2020 May;103(5):4218-4235. doi: 10.3168/jds.2019-17194. Epub 2020 Feb 26.
Starch digestion in the small intestine in ruminants is relatively lower compared with that in monogastric animals, likely due to low pancreatic α-amylase secretion. Previous studies suggested that leucine could increase pancreatic α-amylase secretion in the small intestine of heifers cannulated with abomasal, duodenal, and ileal catheters. However, the surgical procedures probably have an effect on pancreatic function. Thus, we used rumen-protected leucine (RP-Leu) to explore its effect on small intestinal digestion of starch in calves without any surgery in 3 experiments. The first experiment was to explore whether RP-Leu could improve post-ruminal starch digestion in 5-mo-old calves (158 ± 19 kg body weight ± standard deviation). We found that RP-Leu did not affect rumen fermentation profile or whole-tract starch digestibility, but it increased blood glucose concentration and fecal pH and decreased fecal propionate molar proportion. Additionally, RP-Leu increased fibrolytic genera Ruminiclostridium and Pseudobutyrivibrio and decreased the amylolytic genus of Faecalibacterium. The second experiment compared RP-Leu and rumen-protected lysine (RP-Lys) for their effects on post-ruminal starch digestion in 6-mo-old calves (201 ± 24 kg body weight). The responses of blood glucose concentration, fecal pH, fecal propionate proportion, and starch digestibility to RP-Leu supplementation were similar to those observed in experiment 1. Cellulolytic family Ruminococcaceae and Bacteroidales BS11 gut group tended to be increased by RP-Leu. In contrast, RP-Lys showed no significant influence on the above measurements. The third experiment determined the interaction between RP-Leu and rumen-escape starch (RES) on the small intestinal digestion of starch in 8-mo-old calves (289 ± 26 kg body weight). An interaction between RP-Leu and RES levels was observed in fecal butyrate concentration and the relative abundance of family Bacteroidaceae, and genera Ruminococcaceae UCG-005 and Bacteroides. We found that RP-Leu tended to increase the abundance of fecal Firmicutes and decrease Spirochaetae. In conclusion, RP-Leu, but not RP-Lys, increased blood glucose concentration and decreased the amount of starch fermented in the hindgut in a RES dose-dependent manner, suggesting that RP-Leu might stimulate starch digestion in the small intestine.
反刍动物小肠中的淀粉消化率相对较低，这可能是由于胰腺 α-淀粉酶分泌较低。先前的研究表明，亮氨酸可以增加瘤胃、十二指肠和回肠导管插管小母牛的小肠胰腺 α-淀粉酶分泌。然而，手术程序可能会对胰腺功能产生影响。因此，我们在 3 个实验中使用包被亮氨酸（RP-Leu）来研究其对无手术小牛小肠淀粉消化的影响。第一个实验是探讨 RP-Leu 是否可以改善 5 月龄小牛（158±19kg 体重±标准差）的瘤后淀粉消化。我们发现，RP-Leu 不会影响瘤胃发酵特性或全肠道淀粉消化率，但会增加血糖浓度和粪便 pH 值，降低粪便丙酸摩尔比例。此外，RP-Leu 增加了纤维分解菌 Ruminiclostridium 和 Pseudobutyrivibrio 的数量，减少了淀粉分解菌 Faecalibacterium 的数量。第二个实验比较了 RP-Leu 和包被赖氨酸（RP-Lys）对 6 月龄小牛（201±24kg 体重）瘤后淀粉消化的影响。补充 RP-Leu 后，血糖浓度、粪便 pH 值、粪便丙酸比例和淀粉消化率的反应与实验 1 观察到的相似。纤维分解菌 Ruminococcaceae 和拟杆菌门 BS11 肠道群的数量有增加的趋势。相比之下，RP-Lys 对上述测量没有显著影响。第三个实验确定了 RP-Leu 和瘤胃逃逸淀粉（RES）在 8 月龄小牛（289±26kg 体重）小肠淀粉消化中的相互作用。在粪便丁酸浓度和拟杆菌科、Ruminococcaceae UCG-005 和 Bacteroides 属的相对丰度上观察到 RP-Leu 和 RES 水平之间的相互作用。我们发现，RP-Leu 倾向于增加粪便厚壁菌门的丰度，减少螺旋体菌门的丰度。总之，RP-Leu（而非 RP-Lys）以 RES 剂量依赖的方式增加血糖浓度并减少后肠发酵的淀粉量，表明 RP-Leu 可能刺激小肠淀粉消化。
