■畜牧业青贮饲料使用不当引起的乳酸摄入过多对瘤胃发酵有不利影响,如瘤胃酸中毒。D-乳酸在瘤胃上皮细胞中的吸收和代谢速度慢于L-乳酸,使D-乳酸更容易积累并诱发瘤胃酸中毒。因此,本试验旨在通过体外系统研究饲粮D-乳酸水平对肉牛瘤胃发酵的影响及其作用机制。
■本实验采用单因素随机试验设计,5天适应,3天样本采集。使用三种治疗(n=8/治疗):(1)D-LA(0.3%),含0.3%的基础发酵底物(干物质,DM基础)D-乳酸;(2)D-LA(0.75%),含0.75%(DM基础)D-乳酸的基础发酵底物;和(3)D-LA(1.2%),含1.2%(DM基础)D-乳酸的基础发酵底物。
■随着日粮D-乳酸水平的增加,总天然气的日产量,氢气和甲烷,以及乙酸盐的瘤胃浓度,丙酸盐,丁酸盐,异丁酸,戊酸盐,异戊酸,总挥发性脂肪酸和D-乳酸增加(p<0.05),但瘤胃pH值和乙酸盐/丙酸盐比值降低(p<0.05)。基于Bray-Curtis距离的主坐标分析表明,增加日粮D-乳酸水平可显著影响瘤胃细菌群落结构(p<0.05)。但对瘤胃真核生物群落结构无显著影响(p>0.05)。NK4A214_group,ruminococus_gauvreaii_group,真细菌_氧化还原_基团,大肠杆菌志贺氏菌,D-LA(1.2%)组(p<0.05)富含Marvinbryantia和Entodinium,D-LA(0.3%)组中WCHB1-41,vadinBE97,梭状芽胞杆菌_sensu_stricto_1,厌氧菌和反刍动物富集(p<0.05)。瘤胃微生物组成的变化影响瘤胃代谢,主要集中在糖胺聚糖的生物合成(p<0.05)。
■总的来说,饲喂D-乳酸含量高的全株玉米青贮不能诱发瘤胃酸中毒,膳食D-乳酸代谢为挥发性脂肪酸增加了肉牛的能量供应。然而,它还增加了肉牛中瘤胃CH4的排放和机会性病原体大肠杆菌-志贺氏菌的相对丰度。细菌和大肠杆菌志贺氏菌的相对丰度可能受糖胺聚糖的影响,反映了瘤胃微生物与代谢产物之间的相互作用。
UNASSIGNED: Excessive intake of lactate caused by improper use of silage in animal husbandry has adverse effects on rumen fermentation, such as rumen acidosis. The speed of absorption and metabolism of D-lactate in rumen epithelial cells was slower than that of L-lactate, making D-lactate more prone to accumulate and induce rumen acidosis. Therefore, this study was conducted to explore the effects of dietary D-lactate levels on rumen fermentation of beef cattle and its mechanism in an in vitro system.
UNASSIGNED: This experiment was adopted in single-factor random trial design, with 5 days for adaptation and 3 days for sample collection. Three treatments (n = 8/treatment) were used: (1) D-LA (0.3%), basal fermentation substrate with 0.3% (dry matter, DM basis) D-lactate; (2) D-LA (0.75%), basal fermentation substrate with 0.75% (DM basis) D-lactate; and (3) D-LA (1.2%), basal fermentation substrate with 1.2% (DM basis) D-lactate.
UNASSIGNED: With the dietary D-lactate levels increased, the daily production of total gas, hydrogen and methane, as well as the ruminal concentrations of acetate, propionate, butyrate, isobutyrate, valerate, isovalerate, total volatile fatty acid and D-lactate increased (p < 0.05), but the ruminal pH and acetate/propionate ratios decreased (p < 0.05). Principle coordinate analysis based on Bray-Curtis distance showed that increasing dietary D-lactate levels could significantly affect the structure of rumen bacterial community (p < 0.05), but had no significant effect on the structure of rumen eukaryotic community (p > 0.05). NK4A214_group, Ruminococcus_gauvreauii_group, Eubacterium_oxidoreducens_group, Escherichia-Shigella, Marvinbryantia and Entodinium were enriched in D-LA (1.2%) group (p < 0.05), as well as WCHB1-41, vadinBE97, Clostridium_sensu_stricto_1, Anaeroplasma and Ruminococcus were enriched in D-LA (0.3%) group (p < 0.05). Changes in the composition of ruminal microorganisms affected rumen metabolism, mainly focus on the biosynthesis of glycosaminoglycans (p < 0.05).
UNASSIGNED: Overall, feeding whole-plant corn silage with high D-lactate content could not induce rumen acidosis, and the metabolization of dietary D-lactate into volatile fatty acids increased the energy supply of beef cattle. However, it also increased the ruminal CH4 emissions and the relative abundance of opportunistic pathogen Escherichia-Shigella in beef cattle. The relative abundance of Verrucomicrobiota and Escherichia-Shigella may be influenced by glycosaminoglycans, reflecting the interaction between rumen microorganisms and metabolites.