Evaluation of bulk milk analyses of acetone, urea, and the fat-lactose-quotient as diagnostic aids in preventive veterinary medicine

The purpose of this study was to evaluate the use of additional acetone and urea analyses to the established milk quality system (protein, fat, lactose, and somatic cell count) in bulk milk samples twice a month. Samples were obtained from 44/93 herds in a lowland/highland area. When ranging herds with most acetone values over 0.24 mmol/l (90th percentile), only two out of 10 herds would be on a corresponding list when ranged for highest ketosis treatment incidence. Most high acetone values occur after periods with concentrated calvings, but also in periods without calvings, presumably because of feeding with inferior silage high in butyric acid. Milk fat concentration, milk lactose concentration and the interaction term between these, the fat-lactose-quotient, show the largest absolute values in all three models with ketosis treatment incidence, milk protein concentration, and milk yield as dependent variables in general linear analyses on standardized variables. Acetone and urea concentrations in bulk milk show only small absolute values or are omitted from the models. The practical conclusion from these analyses on bulk milk samples to be used by advisory personnel is small, but it seems that high bulk milk fat concentrations and low lactose concentrations are unfavourable when it comes to ketosis treatment incidence, but favourable when it comes to milk protein concentration. Bulk milk acetone concentrations as a measure of the energy supply in herds must only be interpreted after calving intensity and silage quality are assessed.