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bivariate models where the response variables were the observations on one trait expressed in one system and the same trait in the other system. The breeding values obtained by each of these bivariate models were used to compute the correlation between EBV in an intensive fattening system and pasture and to compute the R 2 -adjusted of the regression of EBV in intensive against EBV in pasture. Results and discussionOur results show the existence of significant GEI for growth during the post weaning period in Creole cattle, fattened in two contrasted environments. The evolution of the heritability of live weight during the post weaning period differ in each system, and the correlation between weight measured in both systems is reduced as age increases. GEI was significant also for yearling weight, average daily gain, slaughter weight, hot carcass weight and adipose tissue weight. The genetic correlations between each trait expressed in an intensive fattening system and the same trait expressed in a pasture spanned from 0.31 to 0.93. These results were in accordance with previous studies performed in the tropics (Mené ndez and Mandonnet, 2006). The differences between the genetic correlations between the different traits, estimated in an intensive fattening system, and the corresponding correlations estimated in a pasture spanned from 20.53 to 0.44, and the differences between the phenotypic correlations spanned from 20.22 to 0.18. Due to the low number of animals included in the analysis and the number of offspring per sire, high standard errors of the estimates were obtained. For this reason, these differences cannot be considered as significant, except for the relationship between the empty digestive tract weight and the other traits, which were higher in pasture than in intensive fattening. This result suggests two hypotheses: that the efficiency of the digestive system of Creole cattle is such that it can extract from low nutritional level foodstuffs enough resources to be allocated simultaneously both to production traits and its own energy deposit (de Jong and van Noordwijk, 1992); and that this efficiency could be due to the higher weight of the digestive tract observed in pasture with respect to the intensive fattening system. However, the genetic relationship between tissue deposition and growth potential does not appear to differ between systems. ConclusionThe design of breeding plans in the tropics should consider GEI affecting growth traits and carcass traits, because it can cause the expected genetic gain of the population to mismatch its expectation. Whereas, correlated responses to selection between traits in each system are expected to be similar.