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首页> 外文会议>奶牛营养与牛奶质量国际研讨会(ist International Symposium on Dairy Cow Nutrition and Milk Quality) >Nutritional Management of Dairy Cows During the Transition Period
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Nutritional Management of Dairy Cows During the Transition Period

机译：转型期奶牛的营养管理

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摘要

Dry period and transition nutritional strategies may be evaluated based on their influence on critical factors of 1) dry matter intake (DMI) around and after parturition, 2) subsequent milk production and composition, 3) degree of postpartal negative energy balance and body fat mobilization, 4) concentrations of energy-yielding compounds (triglycerides and glycogen) in liver, 5) calcium homeostasis, and 6) metabolic and ruminal adaptations to lactation. Obesity at calving is a well-known risk factor for health problems and suboptimal productive performance. Likewise, extreme under-nutrition may adversely affect postpartum outcomes. Based on the body of research conducted, feeding to approximately meet the requirements of cows for energy and protein (and of course other nutrients such as minerals and vitamins), without greatly exceeding energy requirements, is the approach most likely to achieve consistent success. This concept may be applied by several approaches and with varying dietary formulation, ranging from limit-feeding of moderate-energy diets to ad libitum feeding of high-roughage low-energy diets. Requirements for metabolizable energy for dry cows and first-gestation heifers are quite modest (ca. 100 MJ) and can be met with relatively low-energy diets. Conversely, diets high in maize silage or whole-crop cereals and supplemented with additional concentrates will result in an excess of energy intake relative to requirements, as cows do not regulate intake to meet energy needs over the short-term. Energy over-consumption leads to marked decreases in DMI leading up to calving. The accumulated evidence is that these higher energy diets fed during the dry period do not increase subsequent milk production or energy balance. Our laboratory has obtained data from several lines of evidence to indicate that overfeeding results in changes analogous to obesity, with poor DMI, substantial body fat mobilization, increased fat deposition in the liver, and, if severe, impairment of liver function. Providing a consistent balanced diet of high bulk that will limit total energy intake with ad libitum DMI minimizes the drop in DMI before calving. Data available to date indicate that these high-bulk diets, if formulated and fed to meet nutrient requirements of the cows, decrease body fat mobilization, blood ketones, and liver fat accumulation postpartum. Bulky feeds such as straw must be processed so that cows do not sort the total mixed ration (TMR). The conclusions here are in agreement with the biologically sensible concept of 'priming the system' for subsequent metabolic adaptations and production, rather than attempting to suppress these adaptations by high energy feeding during the dry period. Controlling energy intake to near the cows' requirements also is consistent with observations in other animals and humans. These concepts must continue to be evaluated under both research and field settings, particularly with regard to reproduction and longevity. On the basis of available scientific data as a whole, however, we conclude that requirements for energy (and other nutrients) should be met but not greatly exceeded during the dry period. Careful feeding management is critical to ensure that formulated nutrient intakes are actually achieved in practice. How do we feed cows during the dry period and transition period to prevent health problems and promote high productivity? Although researched for several decades, the topic remains controversial yet timely for several reasons. Continued increases in milk production per cow, and perhaps more importantly milk energy per cow, demand optimized nutrition to maintain this productivity while keeping cows healthy. As a result of continued selection for high productivity and high peak milk during early lactation, fertility of dairy cows continues to worsen (Garnsworthy and Webb, 1999; Mee, 2004; Pryce et al., 2004). Most of the health problems encountered by dairy cows during lactation occur at or shortly after calving. The incidence of these health problems may be impacted by prepartum nutrition. The feed industry has developed and marketed a large number of additives, products, and programs for dry cows. Many of these products have merit in certain circumstances, but many also are expensive products that carry the potential for overuse when not indicated (Overton and Waldron, 2004). Overall, then, the dry period and transition play a critical role in profitability of dairy farming.
机译：干旱期和过渡期营养策略可根据其对以下关键因素的影响来评估：1）分娩前后的干物质摄入（DMI），2）随后的牛奶生产和组成，3）产后负能量平衡程度和体内脂肪动员，4）肝脏中产生能量的化合物（甘油三酸酯和糖原）的浓度，5）钙稳态，6）代谢和瘤胃对泌乳的适应性。产犊时肥胖是健康问题和生产性能欠佳的众所周知的风险因素。同样，极端的营养不足可能会对产后结局产生不利影响。根据所进行的研究，在不大大超过能量需求的情况下，喂养大约能满足母牛的能量和蛋白质（当然还有其他营养物质，例如矿物质和维生素）的需求，是最可能取得持续成功的方法。可以通过几种方法和不同的饮食配方来应用该概念，范围从中度能量饮食的限饲到高粗饲料低能量饮食的随意饮食。干奶牛和头胎小母牛的代谢能需求非常适中（约100 MJ），并且可以通过相对低能的饮食来满足。相反，由于玉米不能调节摄入量以满足短期能量需求，因此相对于需求量而言，玉米青贮饲料或全谷类谷物中的高热量饮食会导致能量摄入过多。能源过度消耗会导致DMI显着下降，从而导致产犊。积累的证据表明，这些在干燥期间进食的高能量饮食不会增加随后的牛奶产量或能量平衡。我们的实验室已经从多条证据中获得了数据，这些数据表明，过度喂养会导致类似于肥胖的变化，DMI差，体内大量脂肪动员，肝脏中脂肪沉积增加以及严重的肝功能损害。随意提供高体重的均衡饮食，可以限制总能量摄入，而随意添加DMI可将产犊前DMI的下降降至最低。迄今可获得的数据表明，如果配制和饲喂满足母牛营养需求的这些高脂肪日粮，会减少人体脂肪动员，血酮和产后肝脂肪蓄积。必须处理大块的饲料（例如稻草），以免母牛不对总混合日粮（TMR）进行分类。这里的结论与为后续的代谢适应和生产“启动系统”的生物学上合理的概念相吻合，而不是试图通过在干旱时期通过高能量进食来抑制这些适应。将能量摄入控制在接近母牛的需求水平也与其他动物和人类的观察结果一致。这些概念必须继续在研究和田野环境下进行评估，尤其是在繁殖和寿命方面。但是，根据整体可得的科学数据，我们得出结论，应满足能量（和其他营养素）的需求，但在干燥期不要过多。仔细的喂养管理对于确保实际摄入配方营养至关重要。在干旱时期和过渡时期，我们如何喂养母牛以预防健康问题并提高生产力？尽管进行了数十年的研究，但由于多种原因，该主题仍然存在争议，但仍适时。每头母牛的产奶量持续增长，也许更重要的是每头母牛的产奶量不断增加，需要优化营养以维持这种生产力，同时保持母牛健康。由于在早期哺乳期间不断选择高生产率和高峰值牛奶，奶牛的生育能力继续恶化（Garnsworthy和Webb，1999； Mee，2004； Pryce等，2004）。奶牛泌乳期间遇到的大多数健康问题都在产犊时或产犊后不久发生。这些健康问题的发生可能会受到产前营养的影响。饲料工业已经开发并销售了大量用于干牛的添加剂，产品和程序。这些产品中的许多在某些情况下都有其优点，但许多价格昂贵的产品也有可能在未指明的情况下过度使用（Overton和Waldron，2004年）。总体而言，干旱时期和过渡期对奶牛场的盈利能力起着至关重要的作用。

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