-Four diets based on different vegetal protein concentrates: soya bean meal 48 (SB48 diet), soya bean protein concentrate (SB61 diet), sunflower meal 36 (SF36 diet) and a combination of soya bean meal 48 and potato protein concentrate (SB48-P77 diet) were formulated for the starter period (25-39 days) in early weaned rabbits (25 days of age). These sources of protein accounted for 30% of the total dietary crude protein (CP) content. All diets were formulated to be isonutritive and to meet or exceed all the essential nutrient requirements of growing rabbits. A feeding trial was conducted to measure the effect of the treatments on growth performance in 204 rabbits that were fed ad libitum the experimental diets in the starter period and thereafter received a common feed until 60 d of age. Faecal and ileal apparent digestibility of dry matter (DM) and CP (9 and 7 replicates, respectively) were determined at 35 d of age. The weights and pH of the stomach and caecal contents, ammonia concentration in the caecum and jejunal morphology were also determined (11 rabbits per diet). The treatments did not affect faecal DM and CP digestibility. However, the source of protein affected ileal digestibilities of DM and CP (P < 0.04), which were around 14 and 7% higher for SB61 and SF36 diets, respectively, than for the SB48 diet, whereas the values obtained for the SB48-P77 diet were intermediate. The ileal flux of CP and the N-NH 3 caecal concentration were (P = 0.08 and 0.05, respectively) affected by the source of protein. The highest values were observed in animals fed the SB48-P77 diet, increasing by around 25 and 35%, respectively, compared to the other three diets. The treatments had no effect on digestive traits and jejunal morphology. The differences in ileal digestion efficacy among treatments led to differences (P = 0.008) in food efficiency the first week after weaning, which was higher (10%, as average) in animals fed the SB61 diet than that observed for animals fed the SB48 and SB48-P77 diets, whereas the value obtained for SF36 was intermediate. In this period, the type of diet tended (P = 0.08) to affect daily gain and food efficiency, with the lowest values obtained for the SB48 diet. The treatments had no effect on mortality in the first two weeks after weaning. However, mortality in the whole fattening period was affected by protein source (P = 0.03), since it was higher in animals fed the SB48-P77 diet after weaning than the animals fed the other three diets (34.6 vs. 16.7%, respectively). In conclusion, SF36 and SB61 are the sources of protein that led 461 * Corresponding author: cdeblas@pan.etsia.upm.es Anim. Res. 52 (2003) DOI: 10.1051 to the best growth performances and the lowest mortality rate. The higher efficiency obtained for these feeds might be mainly related to its higher ileal (CP) digestibility.461-471 INRA, EDP Sciences,sources of protein / digestion / growth performance / early weaning / rabbits Résumé -Effet de la source protéique sur la digestion et la croissance de lapereau...