Invited review: Future directions for cow-calf contact research and sustainable on-farm applications.

Prolonged cow-calf contact (CCC) is of growing importance to the dairy sector due to increasing societal interest, implementation of CCC on farms, and research efforts. Incorporating CCC into dairy systems may be a polarizing change for academics and farmers. However, by considering the challenges with curiosity, including those mutual to CCC and non-CCC systems, there may be an opportunity to collectively improve the management of dairy animals. The aim of this review was to describe current issues and constraints in CCC, propose opportunities to advance knowledge of CCC, and inspire forward-thinking questions for dairy systems. There are known challenges for CCC implementation, such as research reproducibility (e.g., suitable controls, validity types) and on-farm application (e.g., farmer perspectives, policies, and corporate standards). To facilitate practical solutions for farmers wanting to adopt CCC we need research describing the effects of CCC systems on animal health and behavior. Already researchers have begun to explore cow and calf performance and health, methods for decreasing stress at weaning and separation (e.g., duration of contact, gradual weaning), foster cows, and opportunities for positive animal welfare in CCC systems (e.g., affiliative and play behavior). However, because dairying takes place in a complex system, changes may affect different facets of the system's sustainability. We suggest that the development of CCC systems should happen in dialog with stakeholders. Cow-calf contact is an uncommon practice in dairy systems and exists in different contexts; thus, there are many questions to address before advice can be given to interested dairy stakeholders. Perhaps, these CCC-related questions are an invitation to contemplate how we want dairy systems to look like in 30 years.