Abstract
The ban of transgenic feed and synthetic amino acids in organic chicken diets has made necessary to find protein-rich feedstuffs which do not alter productive performance. The effect of the faba bean (Vicia faba var. minor) as a partial substitute for soybean on the performance and carcass traits of slow-growing chickens of both sexes reared under the organic method was assessed. The experiment was carried out in the spring and autumn; one thousand birds per season were split into 8 groups (4 groups of males and 4 groups of females, each duplicated) and fed a double phase diet: a common starter diet for 20 days and two different growing-finisher diets containing either soybean (24%; S) or faba bean (16%; F) till the end of the rearing period (120 d). Average values of final live weight, feed intake and daily weight gain were significantly affected by sex, being higher in males than in females; the diets affected performance only in the 21-60 days of age period when the F group grew less and had poorer feed efficiency compared to the S group. Successively, the compensatory growth eliminated differences in slaughter weight. Regarding carcass traits, the diet affected only the ready- to-cook carcass percentage and the carena length, both of which were higher in S birds. Faba beans could be a valuable protein source in the diet of organic chickens when used after the critical starter period.