Dairy Cow Ketosis: Novel Biomarkers for Early Detection of DiseaseRisk

摘要

The incidence rate of periparturient diseases of dairy cows in Canada and elsewhere has increased steadily during the last two decades. In fact, the number of culled cows per dairy herd, per year in Canada has reached more than 50% with metritis, mastitis, and laminitis leading the list. Ketosis also is a major disease of dairy cows given its high incidence rate. Ketosis has been defined as a metabolic disturbance of energy metabolism that affects subclinically more than 40% of periparturient dairy cows in a herd. Another 12-15% of the cows are affected by the clinical form of the disease. This becomes economically important when taking into consideration the impact that both subclinical and clinical forms of ketosis have on the incidence rate of other periparturient diseases and in lowering milk yield. Presently, diagnosis of ketosis is performed by measurement of ketone bodies in various body fluids with blood P-hydroxy-butyric acid (BHBA) as the golden standard. Cows diagnosed with ketosis are treated with solutions containing dextrose or glucose and glucocorticoids aiming to normalize blood glucose and lower ketone bodies. Moreover, antibiotics like monensin have been approved to be used in Canada as feed additives to prevent occurrence of ketosis; however, this has raised concerns of bacterial resistance. Given the side effects of antibiotics, other more natural preventative treatments would be desirable to be developed and used in the future. However, since not all transition dairy cows areaffected by ketosis it would be beneficial to diagnose cows at greater risk of developing ketosis at an earlier stage and treat only those cows with preventative interventions. This necessitates identification and application of new tests that can diagnose cows at risk of developing ketosis at the earliest possible stage of disease. Recently our lab has applied metabolomics technologies to identify new metabolite signatures that are able to indicate with very high sensitivity and specificity dairy cowsat risk of developing ketosis at the beginning of dry off period. These new biomarker sets of ketosis can be used in the future to identify and treat cows at risk of developing ketosis at the earliest possible stage, prior to elevation of ketone bodiesin body fluids. In this article we also will discuss a paradigm switch that is happening with regards to the methodology and the philosophy that the animal science and veterinary scientists are using in approaching the studying of causality and pathomeachisms of disease around parturition.