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Starter crude protein concentrations on growth and intake of dairy calves
The objective of this study was to determine the effects of starter CP levels on growth, intake, feed efficiency, and plasma urea nitrogen (PUN) concentrations of dairy calves on a commercial dairy. In this randomized complete block design, 120 Holstein heifers (BW = 40.3 ± 4.9 kg) were blocked by birth date. Heifers were assigned to starter CP levels of 18, 20, 22, or 24% (as fed). Calves were fed whole milk and allowed ad libitum access to starter. All calves were fed milk 3 times/day and received 5.7 L/d for 14 d, 6.7 L/d from d 15 to 21, and 7.6 L/d from d 22 to one week prior to weaning when calves were reduced to 1.9 L once/d. Calves were weighed at birth and measured every 3 wk for BW, hip height, heart girth circumference (HGC), and hip width. Blood samples were taken at wk 12 and analyzed for PUN. Data were analyzed as repeated measures using the Proc Mixed procedure of SAS. At 12 wk, BW was greater (P < 0.01) for 24% compared to 18% calves (106.9 and 101.4 kg, respectively) with 20% and 22% (103.7 and 104.1 kg, respectively) being similar to all treatments. Overall average daily gain (ADG) for 20% and 22% (0.74 and 0.75 kg/d, respectively) were similar to 18% and 24%, but 18% and 24% (0.72 and 0.78 kg/d, respectively) were different (P < 0.05). Starter intake over the study was similar among treatments at 0.80, 0.83, 0.87, and 0.91 kg/d for 18, 20, 22, and 24%, respectively (P > 0.23). Overall feed efficiency was similar (P > 0.45) among treatments at 1.78, 1.83, 1.92 and 2.0 kg DM intake/kg gain, respectively. Hip height and HGC were similar among treatments (P > 0.55), but hip widths at 12 wk were greater for 22 and 24% (P < 0.05). As CP levels increased from 18% to 24%, PUN concentrations increased among treatments (11.8, 13.1, 15.2, and 16.4 mg/dL, respectively; P < 0.001). Feeding calves increasing levels of CP in starter did not result in differences in skeletal growth, feed efficiency, or overall starter intake. At 12 wk, feeding calves 24% CP starter resulted in greater BW than feeding 18% CP, but was similar to feeding 20 or 22% CP starter. Feeding 18, 20 or 22% CP starter resulted in similar ADG.
Keywords:
Dairy calves, starter, protein