To reduce prevalence of liver abscesses in finishing beef steers, we must evaluate the possibility of pathogens originating from the hind gut as well as the rumen. We hypothesized that pathogens promoting liver abscess formation are located throughout the gut, and increased dietary roughage levels could improve gut integrity over time. Two hundred sixty-three crossbred beef steers (BW = 258 ± 29 kg) were used in a randomized complete block design with 7-8 hd/pen (8 pens/treatment) using a 2 × 2 factorial treatment structure. Steers received steam-flaked corn-based diets with 5 or 15% corn stalk (CS) inclusion (dry matter basis, DMB) and with (TYL) or without (NTYL) tylosin (7.9 g/T; DMB). Half of the pens in each treatment remained on feed for the entire experiment duration (Exp 1) whereas the remaining half were designated for serial slaughter (Exp 2). Steers were fed each day at 0700 h for an average of 220 d (heavy block = 175 d, light block = 233 d). For Exp 2, eight steers were slaughtered on d 0 to obtain initial tissue samples and thereafter one pen/treatment was slaughtered every 56 d. During serial slaughter, dorsal and ventral sac rumen tissue samples were collected for histopathological evaluation along with ruminal, ileal, and colonic tissues for bacterial isolation. Data were analyzed using mixed models; pen was the experimental unit for performance outcomes and individual animal was the experimental unit for bacterial isolation and histopathological data. No interaction (P ≥ 0.40) between tylosin and CS inclusion was detected for ADG or final BW. Interactions were detected for DMI and G:F; both outcomes were similar when tylosin was included in the diet, however both outcomes differed notably without tylosin. Perimeter and length of ventral rumen papillae decreased (P ≤ 0.01) as DOF increased. In contrast, dorsal rumen papillae perimeter and length increased through d112 and then decreased through d231. Corn stalk inclusion rate did not affect the incidence of bacterial species isolated from the ruminal (P = 0.38), ileal (P > 0.15), or colonic (P > 0.37) epithelial tissues. Cattle consuming the TYL diets tended to have decreased (P = 0.06) presence of ileal Fusobacterium necrophorum subsp. necorphorum and increased (P = 0.07) rates of ruminal Salmonella enterica compared to NTYL. Prolonged consumption of a finishing diet, regardless of CS or TYL inclusion, seemed to be the major source of change in rumen epithelial tissue morphology.

为了减少牛肉肥育过程中肝脓肿的发生率，我们必须评估病原体来自后肠和瘤胃的可能性。我们假设促进肝脓肿形成的病原体遍布整个肠道，随着时间的推移，增加膳食粗饲料水平可以改善肠道完整性。263 头杂交牛肉（体重 = 258 ± 29 公斤）被用于随机完整区组设计，7-8 hd/栏（8 栏/处理）使用 2 × 2 因子处理结构。阉牛接受蒸汽压片玉米日粮，其中包含 5% 或 15% 的玉米秸秆 ( CS )（干物质基础，DMB）和（TYL）或不包含（NTYL）) 泰乐菌素 (7.9 g/T; DMB)。每个处理中的一半围栏在整个实验期间保持饲料（实验 1），而剩余的一半被指定用于连续屠宰（实验 2）。公牛每天在 0700 小时喂食平均 220 天（重块 = 175 天，轻块 = 233 天）。对于实验 2，在第 0 天屠宰八头公牛以获得初始组织样本，此后每 56 天屠宰一圈/处理。在连续屠宰期间，收集瘤胃背侧和腹侧囊组织样本进行组织病理学评估，同时收集瘤胃、回肠和结肠组织进行细菌分离。使用混合模型分析数据；pen 是性能结果的实验​​单元，个体动物是细菌分离和组织病理学数据的实验单元。无交互（对于 ADG 或最终 BW，检测到泰乐菌素和 CS 包含之间的P ≥ 0.40。检测到 DMI 和 G:F 的相互作用；当饮食中包含泰乐菌素时，这两种结果相似，但不使用泰乐菌素时，两种结果显着不同。周长和腹侧瘤胃乳头长度减少（P为DOF增加≤0.01）。相比之下，背侧瘤胃乳头周长和长度在 d112 期间增加，然后在 d231 期间减少。玉米秸秆包含率不影响从瘤胃（P  = 0.38）、回肠（P > 0.15）或结肠（P > 0.37）上皮组织中分离出的细菌种类的发生率。食用 TYL 日粮的牛倾向于减少（P  = 0.06）回肠的存在坏死梭杆菌亚种。necorphorum和增加（P  = 0.07）瘤胃率肠沙门氏菌相比NTYL。无论是否添加 CS 或 TYL，长期食用精加工日粮似乎是瘤胃上皮组织形态变化的主要来源。