MEAT TRACEABILITY OF CATTLE BREED: A LIKELIHOOD RATIO APPROACH APPLIED TO STR GENOTYPES

An increasingly concerning commercial problem is the difficulty in tracing back the breed origin of individual beef cuts. Current methods, being based on paper certifications, are vulnerable to fraud. We report the use of DNA profiles from STR loci for inferring the breed of given specimens, using both our published IGM (individual multilocus genotype) method, and a novel approach based on likelihood ratio statistics. We first analyzed 134 unrelated individuals from Limousine and Chianina breeds (67 animals each) for 19 STR. Hardy-Weinberg genotype probabilities were multiplied over loci, separately for the two breeds, in the end obtaining the likelihood ratio (LR) that a given animal originated from one breed rather than the other. The two breeds were perfectly separated (P < 0.001). We then extended the analysis to common breeds available in the Italian market, and generalized the methodology by defining a likelihood function that a given specimen originated from a specific breed. The present work will be useful in defining a set of informative markers to be used in routine analyses to discriminate between beef cattle breeds.