日粮阳阴离子负平衡对预防奶牛围产期产褥热的影响

摘要

奶牛在围产期需经历内分泌、营养、代谢及生理状态上的一系列变化以适应分娩及泌乳的起动.如果营养管理不能较好的满足这些变化,那么奶牛则面临着发生各种围产期疾病的威胁.产褥热是一种常见的营养代谢病,多发于高龄及高产奶牛.奶牛分娩和泌乳的起动造成低血钙症,而当从肠道吸收的和从骨骼中动用的钙不能完全补充从血液中动用的血钙量时,产褥热就会发生.而有效的预防措施是减少产褥热带来经济损失的最佳途径.其中最常用的有效预防方法之一是饲喂阴离子日粮,即使得日粮阳阴离子负平衡(DCAD).这主要是由于日粮负离子平衡引起奶牛轻微的代谢酸中毒,并激发对骨钙的动员和吸收.然而,饲喂阴离子日粮亦存在一些问题:主要是其适口性较差,故可能降低干物质采食量.因此对于阴离子日粮饲喂管理的监控则十分重要,而尿液pH提供了一种有效且相对准确的用来判定添加是否适当的标准.此外,还对近年来此领域相关的研究结果进行了论述和探讨,以便读者了解利用日粮负离子平衡预防围产期奶牛产褥热发生的相关知识.%During transition period,the dairy cow is undergoing numerous changes in endocrine,nutritional,metabolic,and physiological status as she prepares for calving and initiation of lactation.If nutritional management does not meet these challenges,the transition COW is at risk of developing a wide range of health problems soon after parturition.Milk fever is a common metabolic disorder in dairy cattle that generally affects older,high producing COWS.It strikes at the onset of lactation whenever a COW is unable to extract enough calcium from their bones and diet to replace the calcium lost to milk.Prevention is the most desirable means of reducing the economic losses occurring from milk fever.One of the most frequently used strategy for preventing milk fever is feeding acidifying rations(dietary cation-anion difference,DCAD).The addition of anionic salts helps create a negative dietary cation-anion difference(DCAD),which will make the blood of the cow slightly acidic.The response of the cow will be to mobilize and absorb more calcium in attempt to buffer the acid in her bloodstream,which can better prepare her for the time when calcium will be lost in milk.However,there are potential problems on feeding low level DCAD that need to be considered.The major problem encountered is they arc very unpalatable and can reduce dry matter intake.Therefore,it is necessary to closely monitor the close-up pen and precisely control the feeding.Urine pH of the COWS provides a cheap and fairly accurate gauge of the appropriate level of anion supplementation.Additionally,some recent publications and discussed their research results in this area was also reviewed,SO that help readers better understand applying low level DCAD in preventing milk fever in transition cows.