The effect of rearing substrate and space allowance on the behavior and physiology of dairy calves.

The objective of this study was to investigate the effect of rearing substrate and space allowance on the behavior and physiology of dairy calves. At 1 wk of age, 72 calves were moved into 1 of 18 experimental pens (n=4 calves/pen) where they remained until 6 wk of age. Half of the pens had floors covered with quarry stones (QS) and the other half were covered with sawdust (SW). For each substrate type, calves were reared at 1 of 3 space allowances: 1.0, 1.5, or 2.0 m(2)/calf. Behavior was video-recorded continuously for 24 h in the home pen at 2, 4, and 6 wk of age; the time calves spent lying, standing, walking, and running were estimated using 1-min instantaneous scan sampling. Body weight, cleanliness, fecal fluidity, and skin surface temperature were recorded at 1, 4, and 6 wk of age. Escherichia coli numbers were assessed on the skin surface of the shoulder and in feces of calves at 4 and 6 wk of age. Blood samples were taken at 1, 4, and 6 wk of age to measure cortisol, creatine kinase, immunoglobulin G, serum amyloid A, and total protein concentrations. Calves reared on QS spent less time lying and walking and more time standing at 4 and 6 wk of age compared with calves reared on SW. Furthermore, calves reared at a space allowance of 2.0 m(2)/calf spent less time lying and more time standing and walking compared with calves reared at a space allowance of 1.0 and 1.5 m(2)/calf. Calves reared on QS had lower skin surface temperatures compared with calves reared on SW. Fecal fluidity scores were lower in calves reared on QS than SW at 2 wk of age. Fewer E. coli were recovered from the shoulder of calves reared on QS than those of calves reared on SW, but fecal E. coli counts were similar between rearing substrates and space allowances. Serum amyloid A concentrations were lower in calves reared on QS than SW. We detected no effect of rearing substrate or space allowance on body weight, cleanliness, or concentrations of cortisol, creatine kinase, immunoglobulin G, and total protein. In conclusion, lower skin temperature in combination with reduced lying behavior may reflect reduced comfort of calves reared on QS. Furthermore, a space allowance of 2.0 m(2)/calf may provide calves with more opportunity to perform active behaviors.