Hill T M, Bateman H G, Aldrich J M, Schlotterbeck R L, Tanan K G
Akey, Nutrition and Research Center, PO Box 5002, Lewisburg, OH 45338, USA.
J Dairy Sci. 2008 Jun;91(6):2433-42. doi: 10.3168/jds.2007-0610.
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.
小于5周龄且饲喂代乳粉的育种群后备犊牛的氨基酸需求尚未明确界定，并且在有限数量的研究中，使用5至20周龄的哺乳犊牛进行了估算。这4项研究的目的是调查用赖氨酸、蛋氨酸和苏氨酸补充含24%至28%粗蛋白（CP；来自牛奶来源）和17%脂肪的代乳粉的效果，以估算小于5周龄犊牛的最佳需求。荷斯坦公牛犊（初始年龄为3和4日龄，体重43±1千克）自由采食18% CP（按喂食时计）的开食料，并在31至32日龄断奶（28天研究期）。犊牛饲养在无加热设备、有窗帘的犊牛舍中。在研究1中，基于3种CP浓度（24%、26%和28% CP）的组合，每种浓度分别添加或不添加赖氨酸和蛋氨酸，进行了6种代乳粉处理。在研究2和3中，饲喂26% CP和2.34%赖氨酸的代乳粉处理，以测试蛋氨酸浓度（研究2中为0.64%、0.68%和0.72%蛋氨酸，研究3中为0.64%、0.72%和0.80%蛋氨酸）。在研究4中，饲喂26% CP、2.34%赖氨酸和0.72%蛋氨酸的代乳粉处理，以测试苏氨酸浓度（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%，在赖氨酸含量为2.34%时达到最大值。在研究2（线性）和3（二次曲线）中，添加蛋氨酸对ADG的反应分别为13%和7%，在蛋氨酸含量为0.72%时达到平稳状态。在研究4中，添加苏氨酸对ADG或效率没有反应。基于体重增加、饲料效率和血清尿素氮浓度的反应，以每天0.68千克的量饲喂含17%脂肪、以乳清为基础的代乳粉，配方为26% CP、2.34%赖氨酸和0.72%蛋氨酸似乎是最佳的，而给犊牛饲喂更多的CP和必需氨基酸并没有提高ADG和效率。对于平均体重48千克、每天消耗204克CP且日增重0.46千克的小于5周龄犊牛，其需求似乎可以通过17克赖氨酸、0.31的蛋氨酸:赖氨酸比例、0.54的蛋氨酸+半胱氨酸:赖氨酸比例以及小于0.60的苏氨酸:赖氨酸比例来满足。
