A six-week experiment was carried out in Benin to evaluate under tropical conditions the variation in nutritional value of soybean and maize grains due to, respectively, environmental factors and the plant variety. Two soybean grains of the same variety (Jupiter) but grown in two agro-ecological zones and two varieties of white maize grains (Local and DMR-ESRW) produced in the same environmental conditions were compared. These grains were used in four balanced diets for unsexed broiler chickens (Re Bro) from 8 to 49 days of age.
Per kg of dry matter (DM), a difference of about 0.396 MJ of metabolisable energy and 27 g of crude protein content were found between varieties of maize. Crude protein content was identical in both soybean grains, while a difference of 16 g/kg DM was found between them in crude fibre content. In spite of these differences in chemical components, there was no significant effect (P>0.05) of the grains' origin or variety on the growth performance of chickens. The daily feed intake, the daily weight gain, the feed conversion ratio and the final body weight of chickens at 28 and 49 days of age were similar between diets. In addition, the partial substitution of maize by soybean grains to supply mainly the dietary energy did not show an adverse effect of the diet on these variables. However, the variety of maize affected significantly the feed cost and the economic feed efficiency at starter phase.
It can be concluded that under the particular conditions of this experiment, the environmental factors did not change significantly the nutritional value of soybean grains in chickens' diets. The grain of local variety of white maize were suitable at all ages, whereas the grains of DMR-ESRW were more economic in grower than starter broiler chickens feeding.