Invited review: A systematic review of the effects of early separation on dairy cow and calf health

Abstract

Concern from the public is growing regarding early cow-calf separation, yet proponents of this practice maintain that artificial rearing is critical for cow and calf health. Early separation is assumed to reduce the risk of transfer of pathogens from dam to neonatal calf, but a wide range of health benefits associated with extended cow-calf contact has also been documented. The aim of this systematic review was to report and synthesize conclusions from the literature on dairy cow and calf health in conventional rearing versus cow-calf contact systems. Peer-reviewed, published manuscripts, written in English, directly comparing dairy cow or calf health in artificial versus suckling systems, were eligible for inclusion. We conducted 7 targeted searches using Web of Science to identify key literature on important health conditions. The resulting manuscripts underwent a 4-step appraisal process, and further manuscripts were sourced from reference lists. This process resulted in a final sample of 70 articles that addressed cow and calf health. Sufficient literature was available to assess mastitis in cows, and scours, cryptosporidiosis, Johne's disease, pneumonia, immunity, and mortality in calves. The results for cryptosporidiosis, pneumonia, immunity, and mortality were mixed, with some differences between studies likely attributable to flawed comparisons between cohorts. Overall, the articles addressing calf scours and mastitis pointed to beneficial or no effects of suckling. The studies addressing Johne's disease did not find cow-calf contact to be a significant risk factor. In conclusion, the scientific peer-reviewed literature on cow and calf health provides no consistent evidence in support of early separation.

Keywords: cow-calf rearing; maternal contact; nursing; udder health; weaning.

Figure 1

Flowchart depicting the manuscript screening and appraisal process. Note that summing the studies included in the qualitative synthesis in each subsection yields 87 studies, rather than 70. This discrepancy results from the inclusion of 9 studies in 2 specific sections and 4 studies in 3 specific sections. A deletion of the duplicates results in 70 unique studies.

Figure 2

Example of a chain of citations in the Johne's disease literature evaluating the claim that immediate cow-calf separation reduces Johne's disease prevalence. Newborn calf care (Goodger et al., 1996) represents an aggregate of the following management practices: (1) whether colostrum was harvested from a clean udder (free of manure), (2) whether the bottles used to store colostrum were clean, (3) whether colostrum was pooled, and (4) whether calves were permitted extended contact with the dam. MAP = Mycobacterium avium ssp. paratuberculosis.