PDF(Pubmed)
Abstract：
This review paper provides an in-depth analysis of three critical metabolic diseases affecting dairy cattle such as subacute ruminal acidosis (SARA), ketosis, and hypocalcemia. SARA represents a disorder of ruminal fermentation that is characterized by extended periods of depressed ruminal pH below 5.5-5.6. In the long term, dairy herds experiencing SARA usually exhibit secondary signs of the disease, such as episodes of laminitis, weight loss and poor body condition despite adequate energy intake, and unexplained abscesses usually 3-6 months after an episode of SARA. Depressed milk-fat content is commonly used as a diagnostic tool for SARA. A normal milk-fat test in Holstein dairy cows is >4%, so a milk-fat test of <3% can indicate SARA. However, bulk tank testing of milk fat is inappropriate to diagnose SARA at the herd level, so when >4 cows out of 12 and <60 days in milk are suspected to have SARA it can be considered that the herd has a problem. The rapid or abrupt introduction of fresh cows to high-concentrate diets is the most common cause of SARA. Changes in ruminal bacterial populations when exposed to higher concentrate rations require at least about 3 weeks, and it is recommended that concentrate levels increase by no more than 400 g/day during this period to avoid SARA. Ketosis, a prevalent metabolic disorder in dairy cattle, is scrutinized with a focus on its etiological factors and the physiological changes leading to elevated ketone bodies. In total mix ration-fed herds, an increased risk of mastitis and reduced fertility are usually the first clinical signs of ketosis. All dairy cows in early lactation are at risk of ketosis, with most cases occurring in the first 2-4 weeks of lactation. Cows with a body condition score ≥3.75 on a 5-point scale at calving are at a greater risk of ketosis than those with lower body condition scores. The determination of serum or whole blood acetone, acetoacetate, beta-hydroxybutyrate (BHB) concentration, non-esterified fatty acids (NEFA), and liver biopsies is considered the best way to detect and monitor subclinical ketosis, while urine or milk cowside tests can also be used in on-farm monitoring programs. Concentrations >1.0 mmol/L or 1.4 mmol/L blood or serum BHB are considered diagnostic of subclinical ketosis. The standard threshold used for blood is 1.2 mmol/L, which corresponds to thresholds of 100 mcmol/L for milk and 15 mg/dL for urine. Oral administration of propylene glycol (250-400 g, every 24 h for 3-5 days) is the standard and most efficacious treatment, as well as additional therapy with bolus glucose treatment. Hypocalcemia is a disease of adult dairy cows in which acute hypocalcemia causes acute to peracute, afebrile, flaccid paralysis that occurs most commonly at or soon after parturition. Dairy cows are at considerable risk for hypocalcemia at the onset of lactation, when daily calcium excretion suddenly increases from about 10 g to 30 g per day. Cows with hypocalcemia have a more profound decrease in blood calcium concentration-typically below 5.5 mg/dL. The prevention of parturient paresis has been historically approached by feeding cows low-calcium diets during the dry period. Negative calcium balance triggers calcium mobilization before calving and better equips the cow to respond to the massive calcium needs at the onset of lactation. Calcium intake must be limited to <20 g per day for calcium restriction to be effective. The most practical and proven method for monitoring hypocalcemia is by feeding cows an acidogenic diet for ~3 weeks before calving. Throughout the review, emphasis is placed on the importance of early diagnosis and proactive management strategies to mitigate the impact of these metabolic diseases on dairy cattle health and productivity. The comprehensive nature of this paper aims to serve as a valuable resource for veterinarians, researchers, and dairy farmers seeking a deeper understanding of these prevalent metabolic disorders in dairy cattle.
摘要：
本文对影响奶牛亚急性瘤胃酸中毒(SARA)等三种关键代谢病进行了深入分析,酮症,和低钙血症.SARA代表瘤胃发酵的病症,其特征在于瘤胃pH低于5.5-5.6的抑制时间延长。从长远来看,经历SARA的奶牛群通常表现出疾病的继发症状，比如椎板炎的发作，尽管摄入足够的能量，但体重减轻和身体状况不佳，和无法解释的脓肿通常在SARA发作后3-6个月。降低的乳脂含量通常用作SARA的诊断工具。荷斯坦奶牛的正常乳脂测试>4%，因此，<3％的乳脂测试可以表明SARA。然而,牛奶脂肪的散装罐测试不适合在群体水平上诊断SARA，因此，当牛奶中12天和<60天的>4头牛被怀疑患有SARA时，可以认为牛群有问题。将新鲜奶牛快速或突然引入高浓缩日粮是SARA的最常见原因。当暴露于较高浓度的口粮时，瘤胃细菌种群的变化需要至少约3周，并且建议在此期间浓缩物水平增加不超过400g/天,以避免SARA。酮病,奶牛普遍存在的代谢紊乱,重点审查其病因和导致酮体升高的生理变化。在总混合日粮饲喂的牛群中，乳腺炎的风险增加和生育能力下降通常是酮症的第一个临床症状。所有泌乳早期的奶牛都有酮症的风险，大多数病例发生在泌乳的前2-4周。产牛时身体状况评分≥3.75的奶牛比身体状况评分较低的奶牛患酮症的风险更大。血清或全血丙酮的测定，乙酰乙酸酯,β-羟基丁酸酯（BHB）浓度，非酯化脂肪酸（NEFA），肝活检被认为是检测和监测亚临床酮症的最佳方法，而尿液或牛奶整流罩测试也可用于农场监测计划。浓度>1.0mmol/L或1.4mmol/L血液或血清BHB被认为是亚临床酮症的诊断。用于血液的标准阈值为1.2mmol/L，这相当于牛奶的阈值为100mcmol/L，尿液的阈值为15mg/dL。口服丙二醇（250-400g，每24小时3-5天)是标准和最有效的治疗方法，以及额外的治疗与推注葡萄糖治疗。低钙血症是成年奶牛的一种疾病，其中急性低钙血症引起急性至急性，afebrile,最常见于分娩时或分娩后不久的弛缓性麻痹。奶牛在泌乳开始时存在相当大的低钙血症风险,当每日钙排泄突然从每天约10克增加到30克。低钙血症的奶牛的血钙浓度下降幅度更大，通常低于5.5mg/dL。从历史上看，在干旱时期通过饲喂低钙饮食来预防产妇轻瘫。负钙平衡在产牛之前触发钙动员，并更好地使母牛在泌乳开始时对大量钙需求做出反应。钙摄入量必须限制在每天<20g，才能有效限制钙。监测低钙血症的最实用和行之有效的方法是在产牛之前给奶牛喂食产酸饮食约3周。在整个审查过程中，重点放在早期诊断和积极管理策略的重要性，以减轻这些代谢疾病对奶牛健康和生产力的影响。本文的全面性旨在为兽医提供宝贵的资源，研究人员,和奶农寻求对奶牛中这些常见的代谢紊乱有更深入的了解。
