Subclinical hypocalcaemia in dairy cows: definition and implications

During the transition period (the last weeks of gestation and first weeks of lactation), dairy cows face important physiological, metabolic and immunological challenges, which, if not successfully overcome, will impact their productive and reproductive performance. To face these challenges (nutritional and energy requirements imposed by colostrum and lactogenesis, inflammation, infection), cows launch homeorhetic and homeostatic mechanisms. However, these adaptation mechanisms do not guarantee that the cow will have a successful transition period. So it is not surprising that the highest incidence of diseases in dairy cattle is observed in the first 10 days postpartum (Ingvartsen et al, 2003; LeBlanc et al, 2006).

Almost a century ago, it was discovered that episodes of peripartum ataxia, initially known as milk fever, were explained by a drop in blood calcium concentrations (clinical hypocalcaemia). Subsequently, classic epidemiological studies, such as that of Curtis et al (1985), associated clinical hypocalcaemia with the incidence of other typical peripartum diseases (dystocia, retained placenta, metritis, ketosis, displaced abomasum and mastitis). This led to hypocalcaemia being considered a health disorder, which opened a ‘gateway’ to other diseases, and its establishment as a key condition that can determine the failure of the transition period and, consequently, the productive life of the cow (Goff, 2014). For decades, hypocalcaemia has attracted the attention of not only veterinarians, producers and nutritionists, but also researchers and companies (pharmaceutical, nutrition or health support).