Genetic correlations between growth performance and carcass traits of purebred and crossbred pigs raised in tropical and temperate climates

Abstract

In pig breeding, selection commonly takes place in purebred (PB) pigs raised mainly in temperate climates (TEMP) under optimal environmental conditions in nucleus farms. However, pork production typically makes use of crossbred (CB) animals raised in nonstandardized commercial farms, which are located not only in TEMP regions but also in tropical and subtropical regions (TROP). Besides the differences in the genetic background of PB and CB, differences in climate conditions, and differences between nucleus and commercial farms can lower the genetic correlation between the performance of PB in the TEMP (PB_TEMP) and CB in the TROP (CB_TROP). Genetic correlations (r_g) between the performance of PB and CB growing-finishing pigs in TROP and TEMP environments have not been reported yet, due to the scarcity of data in both CB and TROP. Therefore, the present study aimed 1) to verify the presence of genotype × environment interaction (G × E) and 2) to estimate the r_g for carcass and growth performance traits when PB and 3-way CB pigs are raised in 2 different climatic environments (TROP and TEMP). Phenotypic records of 217,332 PB and 195,978 CB, representing 2 climatic environments: TROP (Brazil) and TEMP (Canada, France, and the Netherlands) were available for this study. The PB population consisted of 2 sire lines, and the CB population consisted of terminal 3-way cross progeny generated by crossing sires from one of the PB sire lines with commercially available 2-way maternal sow crosses. G × E appears to be present for average daily gain, protein deposition, and muscle depth given the r_g estimates between PB in both environments (0.64 to 0.79). With the presence of G × E, phenotypes should be collected in TROP when the objective is to improve the performance of CB in the TROP. Also, based on the r_g estimates between PB_TEMP and CB_TROP (0.22 to 0.25), and on the expected responses to selection, selecting based only on the performance of PB_TEMP would give limited genetic progress in the CB_TROP. The r_g estimates between PB_TROP and CB_TROP are high (0.80 to 0.99), suggesting that combined crossbred–purebred selection schemes would probably not be necessary to increase genetic progress in CB_TROP. However, the calculated responses to selection show that when the objective is the improvement of CB_TROP, direct selection based on the performance of CB_TROP has the potential to lead to the higher genetic progress compared with indirect selection on the performance of PB_TROP.