A review of factors affecting the welfare of weaned replacement heifers in pasture-based dairy production systems

The pasture-based replacement dairy heifer is typically housed and managed intensively from birth until weaning, but post-weaning is housed outdoors in paddocks under less intensive management. Little is published about the welfare of the weaned dairy heifer in pasture-based systems. The aim of this review is to consolidate the scientific literature and provide an overview of factors affecting the welfare of weaned heifers on pastoral dairies. Heifer welfare during transition to the milking herd can be optimised through calving support and by pre-exposing heifers to some of the stressful conditions associated with the milking herd. For the former, heifers should be well grown at calving (≥85% mature bodyweight) and could be mated to bulls that will produce a smaller calf (e.g. Jersey bulls, sexed semen to produce a female calf). Sires should be selected for high ease of calving predicted transmitting ability, and farms should develop and implement a calving intervention and assistance policy. Mixing heifers with milking cows prior to calving, exposing them to competitive grazing conditions and training them to the milking parlour may reduce overall stress burden and enhance adaptability, but research is needed to quantify the welfare and productive merit of this sort of program in seasonal pasture-based dairy systems. This review highlights a lack of recent data relating to the management of the replacement heifer between weaning and their first calving. Research needs to document and disseminate modern dairy heifer management practices in pasture-based systems, as these will affect heifer welfare. The following data need to be collected as a priority: (1) frequency that heifers are weighed or receive health assessments, (2) heifer grazing management, (3) frequency and age of surgical removal of supernumerary teats, (4) mortality rate from weaning until the first lactation, and (5) typical procedures to transition heifers to the milking herd, including management of the first calving. There is also a need to document the management and housing conditions of exported dairy heifers living in other countries.