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 < 0.01) ADG (0.37, 0.44, 0.36, and 0.45 kg/d for CP1, CP2, HP1, and HP2, respectively) compared with calves fed lower MR FR (CP1 and HP1). Preweaning ADG (1 to 42 d) were similar (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 < 0.05) for calves fed higher MR FR. Feed conversions from 1 to 56 d were similar (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 < 0.10) of CP by FR interaction from 43 to 56 d suggested that calves fed CP2 had greater feed conversions (0.46, 0.53, 0.46, and 0.49 kg/kg for CP1, CP2, HP1, and HP2, respectively). This suggests a carryover effect on postweaning performance for calves fed CP2. 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.
Bibliographical noteFunding Information:
The authors express appreciation to the farm staff at the University of Minnesota Southern Research and Outreach Center, Waseca, for the care of the dairy calves and assistance in feeding, sample collection, and analyses. The authors gratefully acknowledge Hubbard Feeds (Mankato, MN) for supplying the milk replacer and calf starter products evaluated in this research and for partial financial support. In addition, the authors appreciated the remaining support from the University of Minnesota and the South Dakota State University Foundation. At the time of this study, 2 authors were employed by Hubbard Feeds while the first author's graduate assistantship was funded by Hubbard Feeds. The University of Minnesota and Hubbard Feeds have a partnership for conducting research projects at the Southern Research and Outreach Center. The remaining authors declare no conflict of interest.
© 2020 American Registry of Professional Animal Scientists
- calf starter
- feeding rate
- milk replacer
- protein concentration