MILK ACETONE CONCENTRATION AS AN INDICATOR OF HYPERKETONEMIA IN DAIRY-COWS - THE CRITICAL VALUE REVISED

Acetone concentration in milk is correlated with subclinical and clini cal ketosis and also with milk yield and reproductive efficiency. The purpose of this study was to assess a threshold of milk acetone at whi ch cotes tend to be adversely affected. The critical values were estim ated on data from 11690 lactations where the change in daily milk yiel d from weeks 1 to 2 to weeks 5 to 6 of lactation was evaluated in rela tion to different milk acetone concentrations. Daily milk yield tended to be reduced in cows with acetone concentrations between 0.7 and 1.4 mmol/l, but responses were not entirely consistent. At concentrations >1.4 mmol/l, daily milk yield teas clearly reduced. Long-term milk yi eld (day 0 to 100 and day 0 to 200) teas about 190 kg of 40 g/kg fat-c orrected milk (FCM) less in cows with acetone concentrations >1.4 vis- 8-vis <0.7 mmol/l. Reproductive efficiency was also impaired in cotes with acetone concentrations >1.4 mmol/l; 4.9 days longer interval from calving to first service (first parity and parity 2+ cows) and 5.7 ti mes a greater risk of cystic ovaries (parity 1), compared with cows wi th milk acetone <0.7 mmol/l. However, no significant effects on long-t erm milk yield or on reproductive efficiency (w)ere found in cows with acetone concentrations 0.7 to 1.4 vis-8-vis <0.7mmol/l. The results s uggest that 1.4 mmol/l acetone in milk may be used as the most importa nt critical value, as higher concentrations are detrimental to product ivity The interval 0.7 to 2.4 mmol acetone per I milk may be used as a warning class, since early lactation yield may be reduced.