In an 8-week feeding experiment, 32 growing buck rabbits (Oryctolagus cuniculus) of an average weight of 1366.56±37.54g, were used to assess the effects of inclusion of different ISSN 2166-0379 2015 www.macrothink.org/jas 167 dietary concentrations of Cerium oxide (CeO), a Rare Earth Element, at 0, 50, 100 and 150 ppm on fertility. The animals were randomly allotted to the four dietary groups, each consisting of eight animals per treatment. The Extra-gonadal Sperm Reserve (the sperm stored in the caput, corpus and cauda epididymis), the testes weights and the daily sperm production (DSP) were estimated. The results revealed that the extra-gonadal Sperm Reserves (ESR) were significantly (P<0.05) increased by dietary cerium oxide at 100 ppm inclusion. Sperm reserves were higher in bucks fed dietary cerium oxide compared with those fed control diet and the highest value recorded at 100 ppm level of inclusion. The results also showed that the testes weights and the daily sperm production (DSP) per testes of the buck rabbits were significantly (P<0.05) increased. The testes of the animals fed diets containing 50-150 ppm dietary cerium oxide had good and normal testicular generation and proper process of spermatogenesis. Therefore, feeding diets supplemented with cerium oxide to buck rabbits to be used for breeding would positively influence sperm production. Journal of Agricultural Studies