EVALUATION OF 5 COWSIDE TESTS FOR USE WITH MILK TO DETECT SUBCLINICALKETOSIS IN DAIRY-COWS

The objective of this study was to evaluate the characteristics of fiv e ketone tests for use with milk to detect subclinical ketosis [define d as >1200 mu mol of beta-hydroxybutyrate (BHBA)/L of blood] in dairy cows. The tests studied were the Ketolac(R) BHB strip to detect BHBA ( Hoechst, Unterschleissheim, Germany) and four tests based on sodium ni troprusside to detect acetoacetate (Rothera tests) [Ketostix(R) strip (Bayer, Etobicoke, ON, Canada), Bioketone powder (Societe d' Analyses Biopharmaceutiques, Laval, QC, Canada), Ketocheck(TM) powder (Great St ates, St. Joseph, MO), and Utrecht powder (University of Utrecht, Utre cht, The Netherlands)]. Milk samples (n = 529) from 266 cows in 25 Ont ario dairy herds were used for this investigation. The Ketolac(R) BHB strip at 50 and 100 mu mol of BHBA/L of milk showed sensitivities of 9 2 and 72%, respectively. This test was more sensitive for subclinical ketosis than were any of the Rothera tests. The sensitivities of the R othera tests were 43, 33, 28, and 5%, respectively, for Utrecht powder , Bioketone powder, Ketocheck(TM) powder, and Ketostix(R) strip. The R othera tests were highly specific, as was the Ketolac BHB strip at 200 , 500, and 1000 mu mol of BHBA/L of milk (specificity, >97%). The prev alence of subclinical ketosis was highest during the first 6 wk of lac tation, and a peak was detected during the 2nd wk of lactation. Of the tests evaluated in this study, Ketolac(R) BHB strip was the most usef ul to monitor subclinical ketosis in dairy herds.