Integration into the dairy cow herd: long-term effects of mother contact during the first twelve weeks of life

The objective of this study is to investigate the long-term effects of mother rearing on the ability to cope with the challenge of integration into the cow herd shortly before first parturition. Four groups of heifers with different levels of contact with their mothers during the first twelve weeks of life were compared. Two rearing groups were fed via an automatic milk feeder two (A2, n = 5) or six times (A6, n = 5) a day. The animals in these groups were compared to two treatment groups that were either kept separate from the cow herd and with limited contact with their mothers (M2, n = 9) or permanent access to the herd and their mothers through selection gates (MP, n = 7). At the age of 25 ± 0.2 months, heifers were integrated individually into the cow herd and observed for 33 h. Social and other behaviour of each heifer was recorded by continuous behaviour sampling, and the identity of the nearest neighbour was determined by time sampling every 5 min. Additionally, faecal samples were taken for measurement of adrenocortical activity. For statistical analysis ANOVA was performed with treatment and breed as fixed factors and herd size, except for social behaviour as covariate. For post hoc testing, heifers were allocated to groups according to contact with the mother (M2 and MP; mother) i.e. suckling by the mother compared to automatic feeding (A2 and A6; automat) and according to contact with the herd (MP; permanent suckling vs. M2, A2, A6; no herd). The treatment groups tended to differ in the frequency of self grooming (p = 0.102), with mother-heifers tending to self-groom more often than automat-heifers (p = 0.109). Permanent suckling-heifers performed self-grooming more often than no herd-heifers (p = 0.048). Concerning social behaviour, the treatment groups tended to differ in submissive behaviour (p = 0.062), with mother-heifers being submissive more often than automat-heifers (p = 0.023) and permanent suckling-heifers more often than no herd-heifers (p = 0.055). The increase in the concentration of faecal cortisol metabolites after the first two days of integration tended to be different between the treatment groups (p = 0.088). In our nearest neighbour analysis, one MP-heifer and one M2-heifer could clearly identify their mothers in a herd of 50 cows after 2 years of separation (p< 0.05, over chance level). This suggests that rearing with contact with the mother in the first twelve weeks, even if very limited, may have an effect on later behaviour and may lead to possibly enhanced social skills in dairy heifers.