Feeding an amino acid formulated milk replacer for Holstein calves.

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.