Over a seven months period (from June to December), the trend of the fattening performance was investigated in five plein-air rearing systems utilising the same management and cages but different genetic strains. The trial took place in the north-east of Italy with a continental climate. Animals were moved to plein-air cages after weaning period (38 d; average of weight alive: 1,025g) till the end of the fattening period (82-90 d; average of weight alive: 2,740g). 25 fattening cycles have been considered corresponding to about 33,770 animals. The analysed parameters were: farm, months, genetic strain, daily weight gain (DWG) and mortality causes divided into: respiratory, enteric and others. The results showed that the farm and the genetic strain were not statistically significative vs DWG and mortality. Only farm vs mortality (respiratory diseases) and months vs DWG showed significant effects. In the first one, the significative value (P<0.01) was noticed just in one farm, but considering that the mortality distribution among months is not significant, the difference is probably linked to the management. In the second one, the month vs DWG resulted statistically significative (P<0.05). It probably depends on the high temperatures: in fact, the best DWG was in December (41 g) and the worst was in August (32.6 g). These results are comparable to those obtained in intensive rabbit farms.