Effects of simplified group housing on behavior, welfare, growth performance, and health of preweaned dairy calves on a California dairy.

A total of 42 Holstein heifer calves on a commercial dairy farm were enrolled in groups of three to different housing treatments; IH (n = 21) or GH (n = 21). Each treatment was composed of seven groups of three calves each. Calves in the GH treatment were housed in groups of three from six to ten days until 70 days of age. Individual pens consisted of one polyethylene hutch with a 1.5 m × 1.2 m outside exercise area. Group pens were constructed by assembling three polyethylene hutches with a 1.5 m × 3.6 m outside exercise area of wire panel fencing. Calves were weighed and measured for height at birth and weaning. Diarrhoea and bovine respiratory disease (BRD) scores were recorded daily throughout the pre-weaning period. Cumulative incidence and hazard ratios were estimated for BRD and diarrhoea for GH and IH. A mixed model with pen as a random effect was specified to evaluate the effect of treatment.

Group-housed calves gained 0.64 ± 0.02 kg/day while IH calves gained 0.65 ± 0.02 kg/day. Similarly, there was no evidence for treatment differences in withers height gain in GH calves (0.22 ± 0.01 cm/day) compared with IH calves (0.21 ± 0.01 cm/day). The cumulative incidence of BRD based on the California scoring system in GH calves was 75 ± 9.68% compared with 66.66 ± 10.28% in IH calves. Group-housed calves had a BRD hazard of 1.14 times that of IH calves. The cumulative incidence of diarrhoea (faecal score 3) in GH calves was 100% in comparison to 95.20% ± 4.66% in IH calves. The mean proportion of scan observations of calves feeding on concentrates was significantly higher in GH (0.145 ± 0.004/hour) compared with IH calves (0.076 ± 0.003/hour) during the pre-weaning period.

The study results provide evidence that this simplified GH system provides benefits of GH without detrimental short-term effects on calf growth and health during the pre-weaning period.