Cross validation of cut-off limit estimations for milk indicators of subclinical ketosis

Abstract

Real time analyses of main milk components are attended in milking parlours today. Breeders can know milk composition regularly. Energy (ketosis) milk quotients such as fat/crude protein (F/CP) and fat/lactose (F/L) could be essential for ketosis prevention and losses which can be linked with it. Aim was to do a reciprocal validation of reliability of milk indicators for subclinical ketosis (SK) identifi cation. There were: dairy cows on 1st and other lactations free of clinical and superior subclinical mastitis; 3 herds of Czech Fleckvieh (CF) breed, 3 herds of Holstein (H) breed and 1 herd with CF and H; 329 individual milk samples from summer and winter season and 1st third of lactation. Average milk yield varied from 5,500 to 10,000 kg per lactation. Thresholds of F/CP and F/L were estimated (P0.05) according to SK milk acetone cut-off limit (10 mg.l-1). These were: for fi rst lactation 1.27 (CF) and 1.32 (H), for other lactations 1.52 (CF) and 1.42 (H) in F/CP; for fi rst lactation 0.84 (CF) and 0.84 (H), for other lactations 0.87 (CF) and 0.85 (H) in F/L. They were used for cross validation (P0.001) in the same order: 1.251, 1.31, 1.31 and 1.383 in F/CP; 0.831, 0.821, 0.989 and 0.852 in F/L. Validated cut-off limits are quite similar to their original values. It confi rmes good reliability of original limits. The validated cut-off limits of milk indicators (F/CP and F/L) for SK in early lactation can be used at technological innovation in animal husbandry. Use of both quotients could improve the regular investigation of SK in practice.