Optimal concentrations of lysine, methionine, and threonine in milk replacers for calves less than five weeks of age
Optimal concentrations of lysine, methionine, and threonine in milk replacers for calves less than five weeks of age
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DOI：
10.3168/jds.2007-0610
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发表时间：
2008-06-01
影响因子：
3.5
通讯作者：
Tanan, K. G.
中科院分区：
文献类型：
--
作者：
Hill, T. M.;Bateman, H. G., II;Tanan, K. G.
未明确定义小于5周龄的哺乳替代犊牛和饲喂牛奶的犊牛的AA需要量，并且已在使用5 - 20周龄牛奶饲喂犊牛的有限数量的研究中进行了估计。这4项研究的目的是研究补充含24 - 28%粗蛋白（CP;来自乳源）和17%脂肪的赖氨酸、蛋氨酸和苏氨酸的牛奶添加剂的效果，以估计小于5周龄小牛的最佳需求量。荷斯坦公牛犊（最初3和4日龄，43 +/- 1 kg体重，BW）自由采食18% CP（饲喂）启动剂，并在31至32日龄断奶（28天研究）。小牛被圈养在不加热的窗帘式育儿室中。在研究1中，基于3种CP浓度（24、26和28% CP）的组合饲喂6种牛奶添加剂处理，每种添加或不添加赖氨酸和蛋氨酸。在研究2和3中，饲喂26% CP和2.34% Lys牛奶添加剂处理以检测Met浓度（研究2中为0.64、0.68和0.72% Met，研究3中为0.64、0.72和0.80% Met）。试验4分别饲喂26%CP、2.34%Lys和0.72%Met三种添加剂，测定Thr含量（1.06、1.43和1.80%）。在研究1中，添加赖氨酸和蛋氨酸使平均日增重（ADG）提高了17%，其中2.34%赖氨酸最大化。在研究2（线性）和3（二次）中，对添加Met的ADG响应分别为13%和7%，在0.72% Met时达到平台。在研究4中，没有ADG或效率响应于添加的Thr。根据对增重、饲料效率和血清尿素氮浓度的反应，以0.68 kg/d饲喂26%CP、2.34%Lys和0.72%Met的17%脂肪乳清基乳添加剂似乎是最佳的，而饲喂更多的CP和必需AA并没有提高犊牛的ADG和效率。对于小于5周龄的犊牛，平均体重为48 kg，消耗204 g CP/d，增重0.46 kg BW/d，赖氨酸17 g，蛋氨酸：赖氨酸比为0.31，蛋氨酸+胱氨酸：赖氨酸比为0.54，苏氨酸：赖氨酸比小于0.60。
The AA requirements of herd-replacement calves less than 5 wk old and fed milk replacers are not clearly defined and have been estimated in a limited number of studies using milk-fed calves ranging from 5 to 20 wk of age. The objective of these 4 studies was to investigate the effect of supplementing milk replacers containing 24 to 28% crude protein (CP; from milk sources) and 17% fat with Lys, Met, and Thr to estimate the optimum requirements for calves less than 5 wk of age. Holstein bull calves (initially 3 and 4 d old, 43 +/- 1 kg of body weight, BW) were fed an 18% CP (as-fed) starter ad libitum and weaned at 31 to 32 d of age (28-d studies). Calves were housed in an unheated, curtain-sided nursery. In study 1, 6 milk replacer treatments were fed based on the combination of 3 CP concentrations ( 24, 26, and 28% CP) each with or without added Lys and Met. In studies 2 and 3, 26% CP and 2.34% Lys milk replacer treatments were fed to test the concentration of Met (0.64, 0.68, and 0.72% Met in study 2 and 0.64, 0.72, and 0.80% Met in study 3). In study 4, 26% CP, 2.34% Lys, and 0.72% Met milk replacer treatments were fed to test the concentration of Thr (1.06, 1.43, and 1.80%). There was a 17% improvement in average daily gain (ADG) in study 1 from adding Lys and Met that was maximized with 2.34% Lys. The ADG response to added Met in studies 2 ( linear) and 3 ( quadratic) were 13 and 7%, respectively, with a plateau at 0.72% Met. There was no ADG or efficiency response to added Thr in study 4. Formulating 17% fat, whey-based milk replacers fed at 0.68 kg/d to 26% CP, 2.34% Lys, and 0.72% Met appeared optimum based on responses of body weight gain, feed efficiency, and serum concentrations of urea nitrogen, while feeding calves more CP and essential AA did not improved ADG and efficiency. Requirements for calves less than 5 wk old, averaging 48 kg of BW, consuming 204 g of CP/d, and gaining 0.46 kg of BW/d, appeared to be met with 17 g of Lys, 0.31 Met:Lys ratio, 0.54 Met+Cys:Lys ratio, and a Thr:Lys ratio less than 0.60.