The transition period—approximately three weeks before and three weeks after calving—is the highest-risk welfare period for dairy cows. The metabolic and physiological demands of parturition and lactation onset create vulnerability to multiple disease conditions with significant welfare implications.
As calving approaches, cows experience profound physiological changes: declining dry matter intake, increasing fetal demands for nutrients, and preparation for lactation onset requiring massive metabolic mobilisation. Simultaneously, immune function is suppressed around parturition—creating vulnerability to infection. The combination of negative energy balance, immune suppression, and tissue mobilisation creates a cascade of potential welfare problems.
In early lactation, cows cannot consume sufficient feed to meet energy demands, entering negative energy balance (NEB). Body fat mobilisation produces non-esterified fatty acids (NEFA), which overwhelm the liver's processing capacity, producing ketone bodies. Subclinical ketosis (elevated ketones without clinical signs) affects 25-40% of cows in early lactation; clinical ketosis causes reduced appetite, milk yield depression, and neurological signs. Chronic ketosis compromises welfare through weeks of suboptimal metabolic function.
Displacement of the abomasum (dairy cow's fourth stomach compartment)—most commonly left displacement (LDA)—occurs in 2-8% of transition cows. It causes reduced appetite, milk yield depression, and pain from visceral distension. Surgical correction (roll and toggle, bar suture, omentopexy) is required. Risk factors include high-energy pre-calving diets, hypocalcaemia, and twin births—all amenable to preventive management.
Hypocalcaemia occurs when calcium mobilisation for colostrum and milk production exceeds dietary supply. Clinical milk fever causes recumbency, muscle weakness, cold extremities, and death if untreated. Subclinical hypocalcaemia (SHC) affects 25-50% of multiparous cows and predisposes to mastitis, metritis, displaced abomasum, and retained placenta. Dietary cation-anion balance (DCAB) manipulation, calcium boluses, and appropriate pre-calving mineral nutrition reduce incidence.
Post-calving uterine infection (metritis) affects 15-40% of dairy cows, causing fever, reduced appetite, and malodorous discharge. Severe metritis causes systemic sepsis and significant welfare compromise. Prevalence is influenced by calving management, body condition, retained placenta, and twin births. Prompt identification through temperature monitoring and appropriate treatment (antimicrobials, supportive care) reduces suffering duration and fertility impacts.
Successful transition management integrates multiple preventive strategies: appropriate pre-calving body condition (BCS 2.75-3.25); DCAB-balanced pre-calving diet; adequate space in dry cow and maternity pens; minimal stress and regrouping; colostrum management; and close observation post-calving. Transition health programmes developed with farm veterinarians and including regular metabolic profiling (NEFA, betahydroxybutyrate monitoring) provide systematic risk management.