Table 23.

Summary of main welfare effects reported in the literature depending on age at grouping

Age at grouping	Positive effects on welfare	Negative effects on welfare	Reference
Group housed between 3 and 6 days old	ABM – Vocalisations Calves paired between 3 and 6 days vocalised less in the post‐weaning period compared with calves group housed at day 28.		Bolt et al. (2017)
Group housed from 6 days old	ABM – Learning ability More calves group‐housed from day 6 learned a reversal task compared with calves housed individually ABM – Mixed ration (grain, silage and hay) intake No differences in intake between calves paired at 6 days and 6 weeks.		Meagher et al. (2015)
	ABM – Concentrate intake Calves paired at 6 days consumed more concentrate than calves paired at 6 weeks		Costa et al. (2015)
Group housed at 9–12 days		ABM – Respiratory disease Prevalence of respiratory disease was higher in calves group housed at 9–12 days compared with calves group housed 1 week later (at 13–19 days old)	Svensson and Liberg (2006)
Group housed from 3 weeks old	ABM – Social behaviour Calves housed in pairs from 3 weeks onwards performed more social behaviour than calves that remained in individual pens		Duve and Jensen (2012)