EVALUATION OF ADDITIONAL ACETONE AND UREA ANALYSES, AND OF THE FAT-LACTOSE-QUOTIENT IN COW MILK SAMPLES IN THE HERD RECORDING-SYSTEM IN NORWAY

The purpose of this study was to evaluate the use of additional aceton e and urea analyses to the established herd recording system (protein, fat, lactose, and somatic cell count) in cow milk samples every secon d month. Samples were obtained from 43/82 herds (800/1368 cows) in a l owland/highland area. Acetone concentrations (mmol/l) were classified into acetone classes 1 (<0.7); 2 (0.7-1.4); and 3 (>1.4). There was an association between increasing acetone class and increasing ketosis i ncidence in herd (Kendall's Tau-b = 0.13). The highest percentage freq uencies of acetone classes 2 and 3 were in weeks 4-6 postpartum. Milk yield, urea, and lactose were significantly lower; milk protein not di fferent, and milk fat was significantly higher in herds with high keto sis incidence and in cows in acetone classes 2 and 3. General linear m odels, obtained by backward elimination of non-significant variables, showed that milk protein was negatively associated to milk yield and p ositively associated to milk far. Milk yield decreased, and milk fat c oncentration increased with increasing acetone level. Milk fat and mil k lactose were negatively associated, and a fat-lactose-quotient might be promising in a model to rule out subclinical ketosis cows.