Genetic parameters of performance tested traits in Maremmana and Podolica breeds

Nowadays, performance testing is still the main selection tool for beef and dual purpose breeds, and also rustic breeds as Maremmana (M) and Podolica (P) are selected through this method. The test stations are managed by ANABIC (Italian beef cattle breeds association), responsible for young bulls recruitment (at 9 months of age), test data collection (over 6 months) and selection of young candidate bulls (at 15 months of age). This study was aimed at estimating genetic parameters for tested traits using performance data of almost 15 years of activity. Data on 757 performance tested bulls (300 for M; 457 for P) born from 1996 to 2009 were used in the study. Animals belonged to 13 and 14 contemporary groups (GR) for M and P, while the number of herds of origin (HR) were 23 and 43, respectively. Traits analysed were average daily gain during test (TADG), obtained by linear regression of weight on age, the fleshiness score (FLESH) and the final morphological score (MORPH), both evaluated at the end of test. Preliminary ANOVA indicated significant effects of GR and HR on all traits in both breeds, and a significant effect of the age at end of test as covariate for FLESH and MORPH. Bayesian bi-traits variance component analysis via gibbs sampling using all available pedigree (1959 for M and 2251 for P, respectively) produced h2 estimates greater for M (0.511 for MORPH; 0.568 for FLESH, and 0.624 for TADG) than for P (0.383 for MORPH; 0.315 for FLESH, and 0.277 for TADG). Positive genetic correlations among traits were estimated for M (from 0.678 between TADG and MORPH to 0.914 between FLESH and MORPH), but milder correlations were obtained for P (from -0.288 between TADG and MORPH to 0.527 between FLESH and MORPH), probably due to greater phenotypic variability and to the lower influence of FLESH on MORPH in P breed as respect to M