ABSTRACT

The feeding of high-concentrate diets commonly results in lowered pH and ruminal dysbiosis which cause shifts in uptake dynamics of short-chain fatty acids (SCFA) and altered epithelial function. Therefore, the current study evaluated the effect of dietary polyunsaturated fatty acids (PUFA) on ruminal fermentation products, gene expression in the ruminal epithelium and the associated changes in ruminal microorganisms in lambs fed a high-concentrate diet. Twenty-six Afshari lambs adapted to a high-concentrate diet during a completely randomised design were fed with a basal diet supplemented with 100 g oil supplement (OS; 60 g sunflower oil and 40 g fish oil) for 10 (OS10), 20 (OS20) and 30 (OS30) d, respectively (n = 6). Lambs with no oil supplementation (OS0, n = 8) were considered as control and slaughtered at d 0 of the experiment, and the remaining lambs were slaughtered at 10, 20 and 30 d on feed. After slaughter, ruminal digesta was collected for evaluating fermentation and microbial community. Ruminal papillae were taken for assessment of epithelial gene expression. Compared with OS0 lambs, supplemental PUFA in OS30 lambs tended to decrease total SCFA concentration with decreased acetic and increased propionic acid concentrations. Acetate:propionate ratios were decreased and ruminal pH was increased in OS20 and OS30 lambs compared to OS0. All groups with included OS had decreased concentrations of iso-valeric and valeric acids compared to OS0. Relative mRNA abundance of monocarboxylate transporter isoforms 1 and 4, insulin-like growth factor binding protein 3, sterol regulatory element-binding proteins 1 and 2 decreased with increasing OS duration. The relative abundance of 3-hydroxy-3-methylglutaryl-CoA synthase 1 mRNA transcript was higher for OS10 and OS20 lambs relative to OS0 lambs. OS20 and OS30 showed a decrease of lipopolysaccharide binding protein mRNA expression compared with OS0. Feeding supplemental PUFA decreased Ciliate protozoa and increased Butyrivibrio fibrisolvens in OS20 and OS30 lambs, whereas Megasphaera elsdenii was increased in OS30 lambs. In conclusion, combined supplementation of sunflower and fish oil to a high-concentrate diet affects the ruminal microbial community with prominent decreases in ruminal ciliate protozoa and increases in B. fibrisolvens and M. elsdenii. These results lead to a more stabilised ruminal pH and a fermentation shift towards more propionate generation. Consideration of nutrients digestion will help to fully understand the benefits of feeding PUFA with a high-concentrate diet.

摘要

饲喂高浓度日粮通常会导致 pH 值降低和瘤胃生态失调，从而导致短链脂肪酸 (SCFA) 摄取动态的变化和上皮功能的改变。因此，目前的研究评估了日粮多不饱和脂肪酸（PUFA）对瘤胃发酵产物、瘤胃上皮基因表达的影响，以及饲喂高浓度日粮的羔羊瘤胃微生物的相关变化。26 只在完全随机设计期间适应高浓度日粮的 Afshari 羔羊在 10 (OS10)、20 (OS10) 和 20 ( OS20) 和 30 (OS30) d，分别为 ( n = 6)。未添加油的羔羊 (OS0, n= 8) 作为对照，在实验的第 0 天屠宰，其余的羔羊在第 10、20 和 30 天喂食。屠宰后，收集瘤胃食糜用于评估发酵和微生物群落。取瘤胃乳头评估上皮基因表达。与 OS0 羔羊相比，OS30 羔羊中补充 PUFA 倾向于降低总 SCFA 浓度，同时降低乙酸和增加丙酸浓度。与 OS0 相比，OS20 和 OS30 羔羊的醋酸盐：丙酸盐比率降低，瘤胃 pH 值增加。包含 OS 的所有组的iso浓度均降低-与OS0相比，戊酸和戊酸。单羧酸转运蛋白亚型 1 和 4、胰岛素样生长因子结合蛋白 3、甾醇调节元件结合蛋白 1 和 2 的相对 mRNA 丰度随着 OS 持续时间的增加而降低。相对于 OS0 羔羊，OS10 和 OS20 羔羊的 3-羟基-3-甲基戊二酰辅酶 A 合酶 1 mRNA 转录物的相对丰度较高。与 OS0 相比，OS20 和 OS30 显示脂多糖结合蛋白 mRNA 表达降低。饲喂补充 PUFA 可减少OS20 和 OS30 羔羊的纤毛虫原生动物并增加溶解丁酸弧菌，而Megasphaera elsdenii在 OS30 羔羊中增加。总之，向高浓度日粮中联合补充向日葵和鱼油会影响瘤胃微生物群落，瘤胃纤毛虫原生动物显着减少，B. fibrisolvens和M. elsdenii 增加。这些结果导致瘤胃 pH 值更稳定，发酵转向更多的丙酸生成。考虑营养物质的消化将有助于充分了解用高浓度饮食喂养 PUFA 的好处。