The management of hypocalcaemia in UK dairy herds

Periparturient milk fever is a widespread metabolic disease within the dairy industry, with a number of potential impacts on the affected animals’ health and productivity in the subsequent lactation that can have a considerable economic impact on farmers. This thesis aimed to investigate current attitudes of both UK dairy farmers and veterinarians towards milk fever and subclinical hypocalcaemia, as well as investigating the feeding of rumen-protected rice bran during the dry period as a milk fever preventative, due to its reported potential as a calcium binder, within a commercial UK dairy herd. A retrospective study was also carried out in order to investigate associations between recorded milk fever events and other outcomes from farm records obtained from 78 UK dairy herds. The levels of agreement between three different blood sample types (serum, lithium heparin plasma, and lithium heparin whole blood) were also considered with regard to testing for concentrations of calcium, magnesium and phosphorous. Questionnaires were distributed to UK dairy farmers and veterinarians in order to assess current attitudes towards milk fever and its prevention. When choosing a prevention strategy, farmers were most concerned with its efficacy, with its ease of use being their second priority. Veterinarians placed a greater importance on metabolic disease than farmers, and it appears that vets may have an important role in education on the subject of hypocalcaemia. A retrospective study of over 59,000 lactations from 78 UK dairy herds found associations between recorded events of milk fever and an increased risk of dystocia, and an increased risk of a cow exiting the herd during the first 30 days of the lactation. Twin pregnancies were associated with a 30% reduction in the risk of milk fever. Rumen-protected rice bran was trialled against a control feed on a UK dairy herd during the dry period as a potential milk fever preventative. Serum calcium concentrations in the control group were significantly higher pre-calving than in the group that received rumen-protected rice bran. Cows fed rumen-protected rice bran were more likely to experience an elevated NEFA concentration post-calving than the control group. No feed-related differences were found in the subsequent 100 day yields. Limits of agreement were examined to investigate whether bovine serum, plasma and whole blood samples can be interchangeably used for the analysis of calcium, phosphorous and magnesium concentrations. Serum and plasma results appeared to show high levels of agreement for all three of the analytes. Whole blood results were more variable. In conclusion, the findings of this thesis provide an insight into the current attitudes within the UK dairy industry towards hypocalcaemia and its prevention. This thesis has also provided information on the effects and practicalities of feeding rumen-protected rice bran during the dry period in a commercial dairy herd and highlights the need for further research on the subject