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

Abstract

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.

Early-life contact with non-maternal adult cows and a pasture-based rearing environment influence behavioural responses of dairy heifers to novelty

“…Heifers of all treatments were then mixed together into the larger replacement heifer herd at pasture at approximately 13 weeks of age. Heifers were managed identically at pasture with some provision of supplementary forage and checked daily and weighed monthly by farm staff, as per typical management of a dairy heifer in a pasture-based system (see Verdon 2023 ).…”

Contact with Mature Cows and Access to Pasture during Early Life Shape Dairy Heifer Behaviour at Integration into the Milking Herd

“…In dairy systems worldwide, common practice has evolved to remove calves from their dams within 24 h of birth and to house adult and juvenile animals separately. Calves are usually reared artificially, and in pasture-based systems, they are typically managed as a single same-age cohort for their first 2 years of life [ 1 ]. Juvenile and pre-parturient replacement heifers in pasture-based systems tend to graze dry-land pasture with little intensity [ 1 ].…”

“…Calves are usually reared artificially, and in pasture-based systems, they are typically managed as a single same-age cohort for their first 2 years of life [ 1 ]. Juvenile and pre-parturient replacement heifers in pasture-based systems tend to graze dry-land pasture with little intensity [ 1 ]. Once they enter the milking herd following calving, they are generally introduced to mature cows for the first time, and the mixed-age milking herd is managed within intensive and competitive grazing regimes [ 1 ].…”

“…Juvenile and pre-parturient replacement heifers in pasture-based systems tend to graze dry-land pasture with little intensity [ 1 ]. Once they enter the milking herd following calving, they are generally introduced to mature cows for the first time, and the mixed-age milking herd is managed within intensive and competitive grazing regimes [ 1 ]. The cow–calf separation system was developed to improve reproductive efficiency and milking ease of the dam, simplify management of both cow and calf and due to the belief that health risks to both cow and calf are more easily mitigated by separation [ 2 ].…”

“…For dairy heifers, the most intensive regrouping experience often occurs around the time of primiparturition, when they are first mixed into a larger herd of older, more experienced and unfamiliar animals. Regrouping has previously been associated with decreased feed intake and milk yield and increased social stress and aggression, mainly during the first 1–2 h but up to 15 days after regrouping [ 1 , 16 ]. Agonistic behaviour is particularly directed by older cows towards naïve heifers and other less dominant herd members [ 15 , 17 , 18 ].…”