Most US dairy calves are raised in individual hutches (IH) for biocontainment purposes and to facilitate monitoring and handling of calves. However, individual hutches typically restrict calves' activity and social interactions. Previous studies showed that group housing (GH) is beneficial to calf welfare and is associated with social benefits. The adoption of group housing (GH) on dairies is hindered by several concerns, with the primary concern being the potential for increased transmission of diseases due to heightened calf-to-calf contact. In light of this, our study aimed to compare the behavior, health, and growth outcomes of calves housed in groups of 3 to individually housed (IH) calves during the preweaning period. A total of 42 Holstein heifer calves on a commercial dairy in Northern California were enrolled in groups of 3 to different housing treatments; IH (n = 21) or GH (n = 21) between July and October 2020. Each treatment was composed of 7 groups of 3 calves each. Calves in the GH treatment were housed in groups of 3 from 6 to 10 d until 70 d of age. Individual pens consisted of one polyethylene hutch with a 1.5 m x 1.2 m outside exercise area. Group pens were constructed by assembling 3 polyethylene hutches with a 1.5 m x 3.6 m outside exercise area of wire panel fencing. Calves were weighed and measured for height at birth and weaning. Diarrhea and bovine respiratory disease (BRD) scores were recorded daily throughout the preweaning period. Cumulative incidence and hazard ratios were estimated for BRD and diarrhea 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/d while IH calves gained 0.65 ± 0.02 kg/d (P = 0.40). Similarly, there was no evidence for treatment differences in withers height gain in GH calves (0.22 ± 0.01cm/d) compared with IH calves (0.21 ± 0.01 cm/d) (P = 0.14). The cumulative incidence of BRD based on California scoring system in GH calves was 75 ± 9.68 compared with 66.66 ± 10.28% in IH calves (P = 0.73). Group-housed calves had a BRD hazard of 1.14 times that of IH calves (95% CI: 1.21-2.40; P = 0.74). The cumulative incidence of diarrhea (fecal score 3) in GH calves was 100% in comparison to 95.20 ± 4.66% in IH calves (P = 0.99). The mean proportion of scan observations of calves feeding on concentrates was significantly higher in GH (0.145 ± 0.004 per h) compared with IH calves (0.076 ± 0.003 per h) during the preweaning period (P < 0.001). The study results provide evidence that this simplified group housing system provides benefits of GH without detrimental short-term impacts during the preweaning period on calf growth and health.
Keywords: behavior; bovine respiratory disease; dairy calves; group housing; growth; hazard ratio; individual housing; welfare.
© 2024, The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).