Department of Animal Science, College of Animal Science and Technology, Southwest University, Beibei, Chongqing400715, P. R. China.
Animal. 2020 Sep;14(9):1876-1884. doi: 10.1017/S1751731120000786. Epub 2020 Apr 16.
Beef cattle are often fed high-concentrate diet (HCD) to achieve high growth rate. However, HCD feeding is strongly associated with metabolic disorders. Mild acid treatment of grains in HCD with 1% hydrochloric acid (HA) followed by neutralization with sodium bicarbonate (SB) might modify rumen fermentation patterns and microbiota, thereby decreasing the negative effects of HCD. This study was thus aimed to investigate the effects of treatment of corn with 1% HA and subsequent neutralization with SB on rumen fermentation and microbiota, inflammatory response and growth performance in beef cattle fed HCD. Eighteen beef cattle were randomly allocated to three groups and each group was fed different diets: low-concentrate diet (LCD) (concentrate : forage = 40 : 60), HCD (concentrate : forage = 60 : 40) or HCD based on treated corn (HCDT) with the same concentrate to forage ratio as the HCD. The corn in the HCDT was steeped in 1% HA (wt/wt) for 48 h and neutralized with SB after HA treatment. The animal trial lasted for 42 days with an adaptation period of 7 days. At the end of the trial, rumen fluid samples were collected for measuring ruminal pH values, short-chain fatty acids, endotoxin (or lipopolysaccharide, LPS) and bacterial microbiota. Plasma samples were collected at the end of the trial to determine the concentrations of plasma LPS, proinflammatory cytokines and acute phase proteins (APPs). The results showed that compared with the LCD, feeding the HCD had better growth performance due to a shift in the ruminal fermentation pattern from acetate towards propionate, butyrate and valerate. However, the HCD decreased ruminal pH and increased ruminal LPS release and the concentrations of plasma proinflammatory cytokines and APPs. Furthermore, feeding the HCD reduced bacterial richness and diversity in the rumen. Treatment of corn increased resistant starch (RS) content. Compared with the HCD, feeding the HCDT reduced ruminal LPS and improved ruminal bacterial microbiota, resulting in decreased inflammation and improved growth performance. In conclusion, although the HCD had better growth performance than the LCD, feeding the HCD promoted the pH reduction and the LPS release in the rumen, disturbed the ruminal bacterial stability and increased inflammatory response. Treatment of corn with HA in combination with subsequent SB neutralization increased the RS content and helped counter the negative effects of feeding HCD to beef steers.
肉牛通常以高浓度日粮（HCD）喂养以实现高生长速度。然而，HCD 喂养与代谢紊乱密切相关。用 1%盐酸（HA）对 HCD 中的谷物进行轻度酸化处理，然后用碳酸氢钠（SB）中和，可能会改变瘤胃发酵模式和微生物群，从而降低 HCD 的负面影响。因此，本研究旨在探讨用 1%HA 处理玉米并随后用 SB 中和对 HCD 喂养肉牛的瘤胃发酵和微生物群、炎症反应和生长性能的影响。18 头肉牛被随机分配到三组，每组饲喂不同的日粮：低浓度日粮（LCD）（精料：粗饲料=40：60）、HCD（精料：粗饲料=60：40）或基于处理过的玉米的 HCD（HCDT），HCDT 的精料与粗饲料的比例与 HCD 相同。HCDT 中的玉米在 1%HA（wt/wt）中浸泡 48 小时，HA 处理后用 SB 中和。动物试验持续 42 天，适应期为 7 天。试验结束时，收集瘤胃液样品以测量瘤胃 pH 值、短链脂肪酸、内毒素（或脂多糖，LPS）和细菌微生物群。试验结束时采集血浆样品，以测定血浆 LPS、促炎细胞因子和急性期蛋白（APP）的浓度。结果表明，与 LCD 相比，由于瘤胃发酵模式从乙酸盐向丙酸盐、丁酸盐和戊酸盐转变，HCD 具有更好的生长性能。然而，HCD 降低了瘤胃 pH 值，增加了瘤胃 LPS 的释放以及血浆促炎细胞因子和 APP 的浓度。此外，HCD 降低了瘤胃中的细菌丰富度和多样性。玉米处理增加了抗性淀粉（RS）的含量。与 HCD 相比，HCDT 的饲喂降低了瘤胃 LPS，改善了瘤胃细菌微生物群，从而减少了炎症并改善了生长性能。总之，尽管 HCD 的生长性能优于 LCD，但 HCD 的饲喂促进了瘤胃 pH 值的降低和 LPS 的释放，扰乱了瘤胃细菌的稳定性并增加了炎症反应。用 HA 处理玉米并随后用 SB 中和增加了 RS 的含量，并有助于抵消 HCD 对肉牛的负面影响。
