FAT PROTEIN RATIO IN FIRST DHI-TEST MILK AS TEST FOR DISPLACED ABOMASUM IN DAIRY-COWS/

First DHI rest milk that was sampled prior to displaced abomasum (DA) diagnosis was used to evaluate milk rat/protein ratio (FPR) for predic tion of subsequent DA in dairy cows. Odds ratio, sensitivity, specific ity, predictive values, and likelihood ratio were determined. Twenty-s even DA cases were matched to three controls per case by herd and calv ing date. Milk was rested 18 ro 23 days (95 % Cl) after calving, which was 9 to Iri days (95 % CI) prior to DX diagnosis. Adjusted for parit y and days in milk, a fat/protein ratio greater than or equal to 1.4 w as 8.6 times more likely (95% CI, 2.8 to 26) to come from a cow subseq uently diagnosed with DX than a fat/protein ratio < 1.4. Using the cut off value of 1.4, the sensitivity of the FPR for DA was 80 % and the specificity was 69 %. A response operating characteristics curve indic ated that the minimum sum of false negative and false positive results was at an FPR cut off value of 1.4. The likelihood ratio indicated th at far/protein ratios greater than or equal to 1.6 are 3.3 times more likely to come from cows that are diagnosed subsequently with DA than from cows without DX. The fat/protein ratio in first DHI test milk mig ht be useful as a test for subsequent DA in dairy cows.