Lyu Zhiqian, Wang Li, Wang Jinrong, Wang Zhenyu, Zhang Shuai, Wang Junjun, Cheng Jinlong, Lai Changhua
State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, No. 2 Yuanmingyuan West Road, Beijing, 100193 China.
INRA-Agrocampus, UMR PEGASE1348, Saint-Gilles, 35000 Rennes, France.
J Anim Sci Biotechnol. 2020 Oct 8;11:99. doi: 10.1186/s40104-020-00505-7. eCollection 2020.
Dietary fiber can be fermented in gut of pigs and the end products of fermentation were short-chain fatty acids (SCFA). The SCFA had positive effects on gut bacteria and host immune system. In addition, SCFA can provide a part of available energy for pigs. However, there were limited reports on the relationship between dietary fiber, gut bacteria, and energy metabolism. Therefore, this study investigated how dietary fiber and enzyme addition impacted energy metabolism by acting on the microbial community and SCFA.
Wheat bran (WB) was added to the corn-soybean meal-based diet at the levels of 12% and 27%, and oat bran (OB) at 15% and 36%. One of each diet was supplemented with or without 5000 U/kg feed of xylanase, so a total of 10 diets were allotted to 60 growing pigs (initial body weight: 27.2 ± 1.2 kg) using a randomized complete block design. The experiment was conducted in 10 consecutive periods using 6 similar open-circuit respiration chambers. Each pig was used for one 20-day period. During each period, six pigs were allowed 14 d to adapt to the diets in metabolic cages followed by 6 d (from d 15 to d 20) in respiration chambers to measure heat production (HP).
Pigs fed 36% OB diets had greater ( < 0.05) nutrient digestibility and net energy (NE) values compared to those fed 27% WB diets. Apparent digestibility coefficients of dry matter (DM) and crude protein (CP) were lower ( < 0.05) in pigs fed 27% WB diets compared with those fed 12% WB diets. Enzyme addition improved ( < 0.05) the NE values (11.37 vs. 12.43 MJ/kg DM) in diets with 27% WB. Supplementation of xylanase did not affect NE values for basal diets, OB diets and 12%WB diets. Compared with diets with 36% OB, pigs fed 27% WB-based diets excreted more total SCFA, acetate and propionate (expressed as g/kg feed DM) in fecal samples of pigs ( < 0.05). Pigs in the WB diets had greater proportion of phylum Bacteroidetes while phylum Firmicutes were greater in pigs fed OB diets ( < 0.05). Pigs fed WB diets had greater ( < 0.05) abundance of Succinivibrio and which were associated with fiber degradation and SCFA production.
Our results indicated diets supplied by high level of OB or WB promote the growth of fiber-degrading bacteria. The differences in fiber composition between WB and OB led to differences in nutrient digestibility and bacterial communities, which were ultimately reflected in energy metabolism. Enzyme supplementation improved nutrient digestibility as well as NE values for 27% WB diets but not for other diets, which indicated that effects of enzyme were related to type and level of dietary fiber in diets.
膳食纤维可在猪的肠道中发酵，发酵终产物为短链脂肪酸（SCFA）。SCFA对肠道细菌和宿主免疫系统有积极作用。此外，SCFA可为猪提供一部分可利用能量。然而，关于膳食纤维、肠道细菌与能量代谢之间关系的报道有限。因此，本研究探讨了膳食纤维和酶的添加如何通过作用于微生物群落和SCFA来影响能量代谢。
将麦麸（WB）以12%和27%的水平添加到基于玉米-豆粕的日粮中，燕麦麸（OB）以15%和36%的水平添加。每种日粮中的一种添加或不添加5000 U/kg饲料的木聚糖酶，因此使用随机完全区组设计将总共10种日粮分配给60头生长猪（初始体重：27.2±1.2 kg）。实验在10个连续周期内使用6个类似的开路呼吸室进行。每头猪用于一个20天的周期。在每个周期中，6头猪先在代谢笼中用14天适应日粮，然后在呼吸室中用6天（从第15天到第20天）测量产热（HP）。
与饲喂27% WB日粮的猪相比，饲喂36% OB日粮的猪具有更高（P<0.05）的养分消化率和净能（NE）值。与饲喂12% WB日粮的猪相比，饲喂27% WB日粮的猪干物质（DM）和粗蛋白（CP）的表观消化率系数较低（P<0.05）。添加酶提高了（P<0.05）含27% WB日粮的NE值（11.37对12.43 MJ/kg DM）。添加木聚糖酶对基础日粮、OB日粮和12% WB日粮的NE值没有影响。与含36% OB的日粮相比，饲喂基于27% WB日粮的猪在粪便样本中排泄的总SCFA、乙酸盐和丙酸盐更多（以g/kg饲料DM表示，P<0.05）。WB日粮组猪的拟杆菌门比例更高，而饲喂OB日粮的猪厚壁菌门比例更高（P<0.05）。饲喂WB日粮的猪中与纤维降解和SCFA产生相关的琥珀酸弧菌和另一种菌的丰度更高（P<0.05）。
我们的结果表明，高水平的OB或WB提供的日粮促进了纤维降解细菌的生长。WB和OB之间纤维组成的差异导致了养分消化率和细菌群落的差异，最终反映在能量代谢上。添加酶提高了含27% WB日粮的养分消化率以及NE值，但对其他日粮没有影响，这表明酶的作用与日粮中膳食纤维的类型和水平有关。
