Figure 1.

Experimental cows were housed in three dynamic group pens inside a free-stall barn [i.e., full contact (FC), no contact (NC), and partial contact PC group pen]. Within the FC group pen, FC calves were kept with the dams in the group pen but had access to a calf creep area with a straw-bedded lying area, water bucket, hay and concentrates. A metal bar hindered cows to access this area. PC calves were housed individually in a straw-bedded calf box for the first 2 weeks, after which they were pair housed in the same box with their similar-aged peer. In each individual calf box ad lib water, hay, and concentrates were provided. The calf boxes were placed behind a wall (1.2 m high) to limit physical contact and prevent suckling. NC calves were housed in an indoor naturally ventilated calf barn in similar pens as PC calves and were also pair housed at 2 weeks of age. W, water; CF, individual concentrate feeder, ⋆ = automated cow brush.