The high cost of poultry feedstuffs has led to the use of tropical root and tuber crops to formulate the balanced and low cost poultry diets. However, utilization of feeds compounded from roots and tubers has been low due to some identified anti-nutritional factors such as cyanide in cassava and high sugar levels in sweet potato which cause diarrhea in chicken. Furthermore, the few studies done on them have been on animals' performance in terms of feed intake/weight gain, with little or no

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... sis on the effect of such feeds on the animals' reproductive performance. A completely randomized block experimental design was carried out to evaluate the effect of diets containing differently processed sweet potato tuber on the fertility and reproductive performance of broiler breeder cocks. Though, the values for semen characteristics were lower in sweet potato-based diets than the maize-based diet, they fell within the recommended levels for the tropics. Grated sweet potato (GP25) had the least semen volume (0.16  0.04 cm 3) while least sperm concentration (2.68  0.44 × 10 9 /cm 3) and sperm output (0.44  0.14 × 10 9 /ml) were obtained in thinly sliced sweet potato (SP 25). Percentage of eggs fertilized was highest in GP 25 and least in Fermented sweet potato (FP 25). Thus, breeder cocks are potentially fertile when fed on diets formulated with sweet potato tuber and that sweet potato tubers may be used as a good substitute for maize in poultry feed when grated or when fermented.