Nagaraja T G, Galyean M L, Cole N A
Department of Animal Sciences and Industry, Kansas State University, Manhattan, USA.
Vet Clin North Am Food Anim Pract. 1998 Jul;14(2):257-77. doi: 10.1016/s0749-0720(15)30253-x.
Mortality from digestive diseases in feedlot cattle is second only to that from respiratory diseases. Acidosis and bloat are the major digestive disorders and are likely to continue because of ongoing attempts to improve the efficiency of beef production by feeding more grain and less roughage. Subacute acidosis is probably the most prevalent form of acidosis in feedlots and is difficult to diagnose because of the absence of overt clinical signs. Ruminal changes in subacute acidosis are not as dramatic as those in acute acidosis. Also, the subacute form is not severe enough to induce systemic acidosis. Ruminal acidosis is also a predisposing factor for many other ailments in feedlot cattle such as laminitis, polioencephalomalacia, sudden death syndrome, and liver abscesses. Control of acidosis is achieved largely by sound nutritional management. Antimicrobial compounds (i.e., ionophores and nonionophores), have become management tools to impart stability to ruminal fermentation, modulate feed intake, and control acidosis. Bloat in feedlot cattle can be of free gas or frothy type. Frothy bloat is more common but is rarely the reason for bloat deaths. The economic impact of bloat results mainly from decreased animal performance. The etiology of bloat is complex and is the result of interactions between three major groups of factors: animal, dietary, and microbial. Presently, an effective method to control frothy bloat in feedlot cattle is not available. Ionophore antibiotics, particularly monensin, have been shown to be effective in decreasing the incidence and severity of bloat in cattle.
饲养场肉牛消化系统疾病导致的死亡率仅次于呼吸系统疾病。酸中毒和瘤胃臌气是主要的消化紊乱疾病，由于人们持续尝试通过增加谷物喂食量、减少粗饲料量来提高牛肉生产效率，这些疾病可能会继续存在。亚急性酸中毒可能是饲养场中最普遍的酸中毒形式，由于缺乏明显的临床症状，很难诊断。亚急性酸中毒时瘤胃的变化不如急性酸中毒时那么显著。此外，亚急性形式的酸中毒程度不足以引发全身性酸中毒。瘤胃酸中毒也是饲养场肉牛许多其他疾病的诱发因素，如蹄叶炎、脑软化、猝死综合征和肝脓肿。酸中毒的控制主要通过合理的营养管理来实现。抗菌化合物（即离子载体和非离子载体）已成为管理工具，用于维持瘤胃发酵的稳定性、调节采食量和控制酸中毒。饲养场肉牛的瘤胃臌气可以是游离气体型或泡沫型。泡沫型瘤胃臌气更常见，但很少是导致瘤胃臌气死亡的原因。瘤胃臌气的经济影响主要源于动物生产性能下降。瘤胃臌气的病因复杂，是动物、饮食和微生物三大类因素相互作用的结果。目前，尚无有效方法控制饲养场肉牛的泡沫型瘤胃臌气。离子载体抗生素，特别是莫能菌素，已被证明可有效降低牛瘤胃臌气的发生率和严重程度。
