Some potential weaning diets formulated from yam species Dioscorea alata variety Bètè bètè and Dioscorea cayenensis variety Lokpa, soybean and cassava have previously been evaluated. In this study, four different diets (unfermented flour made of Dioscorea alata, fermented flour made of Dioscorea alata, unfermented flour made of Dioscorea cayenensis, fermented flour made of Dioscorea cayenensis) were prepared and fed to weaning rats for a period of 28 days. The study aimed to find out the in vivo impact of these yam composite flours. The performance characteristics of the developed products were investigated and compared with those of Cérélac (a commercial weaning food).The body weight change (BWC) of rats fed the different diets was highest in the rats fed Cérélac (3.39 g) followed by rats fed the fermented composite flours (FBBF and FLOF; 1.97 and 2.00 g, respectively) and casein-based diets (2.48 g) and least in rats fed the unfermented composite flour diets (FBBNF and FLONF; 1.60 and 1.51 g, respectively). A similar trend was observed in the total feed and protein intakes of the experimental animals. Moreover, the rat fed fermented composite flours showed high Protein Efficiency Ratio (2.25 -2.37), Biological ), comparable to those obtained with the casein-fed rats. The present study have shown that the values obtained with the test diet, especially for the fermented composite flours compared favourably with the reference diets (Cérélac and casein) in all the parameters investigated and should be considered a good weaning diet from a nutritional point of view.