Measurement of antibodies to gastrointestinal nematodes and liver fluke in meat juice of beef cattle and associations with carcass parameters.

In an effort to develop non-invasive methods for the diagnosis of Ostertagia ostertagi and Fasciola hepatica infection in beef cattle, this study was undertaken to evaluate antibody-detection ELISAs in meat juice samples and to investigate the associations between test results and carcass parameters. Preliminary tests were carried out to determine optimal working dilutions of meat juice samples. The Pearson correlation coefficients between ELISA results (expressed as ODR) of serum and meat juice samples from 90 to 100 cows were R=0.82 and 0.75 for O. ostertagi and F. hepatica, respectively. Next, an abattoir survey in Belgian Blue suckler cows was performed, analysing meat juice samples from 726 animals in spring and 724 animals in autumn 2008, originating from a total of 480 herds. There was a large variation in the observed O. ostertagi and F. hepatica ODRs and inter-seasonal differences were observed for F. hepatica (spring>autumn), but not for O. ostertagi. The relationships between individual parasite-specific ELISA results and carcass parameters (warm carcass weight, conformation score, fat coverage) were investigated by linear or logistic mixed models with herd as a random effect, while the relationship between herd average ELISA results and herd averaged carcass weight was investigated by linear regression with mean cow age and season as covariates. An increase in individual O. ostertagi ODR over the interquartile range was associated with an increased likelihood by 1.3 of a low conformation score (score E vs. S), but no significant associations were found with other carcass parameters. However, herd mean ELISA results were negatively associated with a decrease in the herd average carcass weight (P=0.001 and P=0.09 for O. ostertagi and F. hepatica, respectively). An increase in the herd mean O. ostertagi or F. hepatica ODR over the interquartile range was associated with a decrease in herd mean carcass weight of 9.1 and 3.4 kg, respectively. The implications of these results and the value of monitoring parasitic infections by analysis of meat juice samples from the abattoir are discussed.