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Objective Our previous studies demonstrated that a modified accelerated milk replacer (MR) having a 24:20 CP:fat concentration fed at higher feeding rates (FR) resulted in improved growth performance and G:F, but the result was not linear. The objective of the current study was to evaluate preweaning (d 1 to 42) and postweaning (d 43 to 56) calf performance when a modified accelerated MR was fed at greater FR compared with a MR having similar or greater CP and lower fat concentrations. Materials and Methods A total of 126 (2 to 5 d old) Holstein heifer calves (40.1 ± 0.76 kg) were blocked by birthdate and randomly assigned to 1 of 5 treatments. Treatments of MR fed at 14.7% solids were (1) control (C−): all milk 24:20 MR fed at 0.26 kg at 2×/d from d 1 to 35; (2) C+: C− MR fed at 0.32 kg 2×/d from d 1 to 35; (3) LF: CP and low fat (24:16) MR fed at 0.32 kg 2×/d from d 1 to 35; (4) LF+: LF MR fed at 0.32 kg 2×/d from d 1 to 7 and at 0.39 kg from d 8 to 35; and (5) HP+: high CP:LF MR (26:16) using the same FR as LF+. All MR were fed 1×/d from d 36 to weaning at d 42 with water and 18% CP texturized calf starter offered free choice at all times. Results and Discussion Calves fed C+ had greater (P Implications and Applications This study demonstrates that feeding a modified accelerated MR (24:20) at a moderate FR improves ADG and frame measurements for calves fed MR having similar or different CP and fat concentrations. The development of a modified accelerated feeding program optimized the protein-to-energy ratio for producing a dairy heifer with a frame that is taller and wider, without having a postweaning BW gain slump.

Objective The objective was to evaluate the preweaning (d 1 to 42) and postweaning (d 43 to 56) performance and health of calves fed a 24% CP:20% fat milk replacer (MR) at different feeding rates based on our previous work that calves fed greater feeding rates of MR demonstrated improved growth. Materials and Methods A total of 108 (2- to 5-d-old) Holstein heifer calves (40 ± 0.69 kg) were randomly assigned to 1 of 4 treatments. The same all-milk-protein MR was fed at 14.7% solids, with treatments of (1) control (MR57): MR fed at 0.57 kg daily from d 1 to 35; (2) MR71: MR fed at 0.71 kg daily from d 1 to 35; (3) MR85: MR fed at 0.68 kg daily from d 1 to 7 and at 0.85 kg daily from d 8 to 35; and (4) MR99: MR fed at 0.68 kg daily from d 1 to 7 and at 0.99 kg daily from d 8 to 35. All treatments were fed MR one time per day from d 36 to weaning, after d 42 with water, and an 18% CP texturized calf starter offered free choice. Results and Discussion Preweaning and overall ADG (0.78, 0.82, 0.83, and 0.85 kg/d for MR57, MR71, MR85, and MR99, respectively) were greater (P 0.10) and intermediate. Overall d 1 to 56 calf starter intakes were greater (P 0.10). Preweaning G:F was lowest for calves fed MR57, whereas d 1 to 56 G:F (0.49, 0.52, 0.52, and 0.54 kg/kg of DM) was greater (P Implications and Applications This study demonstrated that higher feeding rate of a 24:20 MR resulted in increased ADG and feed conversion (G:F).

Objective The objective was to evaluate the growth performance by calves fed a conventional milk replacer (MR) or modified accelerated MR (24% CP) to prevent the slump in postweaning calf starter intake and feed efficiency. Materials and Methods A total of 104 (1 to 5 d old) Holstein heifer calves (39.3 ± 0.66 kg) were assigned randomly to 1 of 4 MR treatments to evaluate preweaning (1 to 42 d) and postweaning (43 to 56 d) performance in a 2 × 2 factorial arrangement of CP concentrations [20% CP or 24% CP high protein (HP) with feeding rates (FR) of 0.57 or 0.68 kg/d]. Treatments were MR fed at 15% solids (as fed): (1) control (CP1): a 20% CP:20% fat MR fed at 0.284 kg 2×/d for 35 d; (2) CP2: the 20:20 MR fed at 0.34 kg 2×/d for 35 d; (3) HP1: a 24:20 MR fed at CP1 rate; and (4) HP2: the 24:20 MR fed at CP2 rate. Results and Discussion No interactions of CP by FR were detected for growth parameters. During 1 to 14 d, calves fed higher MR FR (CP2 and HP2) had greater (P 0.10). Intakes of calf starter from 1 to 56 d were similar (P > 0.10) for calves fed MR with different CP concentrations (0.77 and 0.78 kg/d), whereas calf starter intake (0.81 and 0.74 kg/d) was reduced (P 0.01) for calves fed different CP concentrations (0.54 and 0.55 kg/kg) but were improved when fed higher MR FR (0.53 and 0.56 kg/kg). However, a trend (P Implications and Applications Feeding calves a conventional MR (20%CP:20% fat) at different FR with different CP concentrations resulted in similar performance. Feeding a higher CP MR (24% CP:20% fat) at higher FR did not affect preweaning gain of dairy calves.