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Abstract：
The milk-fed calf has a requirement for amino acids (AA) instead of crude protein (CP); however, most milk replacers (MR) are still formulated for CP concentrations. Previous work has demonstrated that feeding a modified MR (24:20; CP:fat @ 0.64 kg/d) improved calf growth performance compared with standard (20:20 @ 0.57 kg/d) and accelerated MR (26:16 @ 0.78 kg/d). The 56-d study objective was to determine if feeding an MR formulated using synthetic AA to achieve the AA concentrations of a 24:20 MR while reducing CP results in similar or enhanced growth performance and/or reduce cost compared with standard MR formulations. Eighty 3- to 5-d-old Holstein bull calves received in two lots (40) within the same week were blocked by body weight (BW) and randomly assigned to one of four MR treatments consisting of 20:20 (20), 22:20 (22), 24:20 (24), and a 22:20 having the AA concentrations of the 24, but with reduced CP (22AA). All MR contain decoquinate and were fed at 0.57 kg/calf daily split into 2×/d feeding for 14 d via bucket, increased to 0.85 kg/calf daily in two feedings until 35 d, and then fed 1×/d at 0.41 kg/calf daily with weaning after day 42. Calves were housed in straw-bedded hutches with ad libitum access to water and pelleted calf starter (CS). All data were statistically analyzed as a randomized complete block design with block considered random with week as a repeated measurement. Initial BW was similar (P > 0.10) across all treatments (42.4 ± 2.2 kg). Calves fed 22AA MR demonstrated greater (P < 0.05) BW compared with calves fed the 24 MR, and calves fed the 20 and 22 MR being intermediate and similar (P > 0.10; 78.7, 78.8, 76.5, and 81.8 kg for 20, 22, 24, and 22AA, respectively). CS intake was greater (P < 0.05) for calves fed 22AA (0.74, 0.78, 0.65, and 0.81 kg/d) compared with calves fed the 20 and 24, but similar (P > 0.10) to calves fed 22. Calves fed 24 MR demonstrated the lowest CS intake. This study demonstrates that similar growth performance can be achieved by feeding an AA fortified MR having a lesser CP concentration, which might reduce feed costs.
摘要：
牛奶喂养的小牛需要氨基酸（AA）而不是粗蛋白（CP）；但是，大多数牛奶替代品（MR）仍按CP浓度配制。先前的工作表明，与标准（20：20@0.57kg/d）和加速MR（26：16@0.78kg/d）相比，饲喂改良的MR（24：20；CP：脂肪@0.64kg/d）可改善小腿生长性能。56-d的研究目的是确定是否饲喂使用合成AA配制的MR以实现24:20MR的AA浓度,同时降低CP导致与标准MR制剂相比相似或增强的生长性能和/或降低成本。在同一周内，在两批（40）中接受的八十只3至5d大的荷斯坦公牛被体重（BW）阻断，并随机分配到由20：20（20）组成的四种MR治疗方法之一，22:20(22)24:20(24),和22:20具有24的AA浓度,但具有降低的CP(22AA)。所有的MR都含有脱喹酸盐，每天以0.57kg/小牛的速度饲喂，分成2×/d，通过桶饲喂14d，在两次喂养中每天增加到0.85公斤/小腿，直到35天，然后在第42天后断奶，每天0.41公斤/只小牛饲喂1×/d。小牛被安置在草床的棚屋中，可以随意取水和颗粒状小牛发酵剂（CS）。将所有数据作为随机完全区组设计进行统计分析,其中区组被认为是随机的,周作为重复测量。所有处理(42.4±2.2kg)的初始BW相似(P>0.10)。与饲喂24MR的小牛相比，饲喂22AAMR的小牛表现出更大的体重（P<0.05），和小牛饲喂20和22MR是中等和相似的(P>0.10;78.7、78.8、76.5和81.8kg，分别为20、22、24和22AA，分别)。与饲喂20和24的小牛相比，饲喂22AA（0.74、0.78、0.65和0.81kg/d）的小牛的CS摄入量更高（P<0.05），但与饲喂22的小牛相似（P>0.10）。饲喂24MR的小牛显示CS摄入量最低。这项研究表明，通过饲喂具有较低CP浓度的AA强化MR可以实现类似的生长性能，这可能会降低饲料成本。
