The transition period — the three weeks before and three weeks after calving — is the most welfare-critical phase of the dairy cow production cycle. Metabolic, immunological, and physiological changes during this period create significant health risks and welfare challenges that require specific management attention.
Metabolic Challenges at Transition
In the weeks before calving, dry matter intake decreases while energy requirements for fetal development and colostrum production increase, creating a negative energy balance that mobilizes body fat reserves. The release of non-esterified fatty acids (NEFAs) from fat mobilization can, in excessive quantities, overwhelm hepatic metabolism and predispose cows to ketosis and fatty liver disease.
Calcium homeostasis is disrupted around calving as the cow transitions from placental to mammary calcium demand. Hypocalcaemia (milk fever) causes muscle weakness, inability to rise, and in severe cases, cardiac and respiratory failure. Subclinical hypocalcaemia — below normal calcium without clinical signs — is even more prevalent and causes increased susceptibility to other transition diseases, reduced immune function, and welfare costs without obvious clinical manifestation.
Immune Suppression and Disease Vulnerability
The transition period is associated with profound immune suppression, creating heightened vulnerability to infectious diseases. Mastitis, metritis (uterine infection), and retained placenta occur most commonly in the first weeks after calving, precisely when immune function is most compromised. The welfare cost of these diseases is substantial: affected cows experience pain, fever, and systemic illness.
Ketosis causes depression, reduced appetite, and weight loss. Fatty liver disease causes hepatic dysfunction with wide-ranging physiological effects. Displaced abomasum requires surgical correction and causes prolonged ill health before diagnosis in subclinical cases. These conditions frequently occur together, with one transition disease predisposing to another.
Welfare-Positive Transition Management
Evidence-based transition management reduces disease incidence and welfare costs. Appropriate dry period nutrition — avoiding overconditioned cows at calving — reduces NEFA mobilization and disease risk. Negative Dietary Cation-Anion Difference (DCAD) diets in the close-up dry period prevent hypocalcaemia. Transition cow monitoring programs with regular clinical assessment and blood sampling detect subclinical disease before it progresses to clinical crisis.
Social management during the transition period — providing adequate space in close-up pens, minimizing social group changes, and ensuring feed bunk space — reduces competitive stress that exacerbates transition disease risk in vulnerable cows.