Tapioca is produced by the tubers of Manihot esculenta Crantz which grow in tropical areas. It is high in starch and very low in protein content, and cheaper than grains. The replacement of grain by tapioca in diets for cattle was studied in an in vivo digestibility trial and two feeding trials. The source of supplemental protein was soya bean meal (SBM) in the first feeding trial and ensiled poultry litter (PL) in the second. Two diets were fed in the digestibility trial: (i) 100% vetch hay and (ii) 50% vetch hay − 50% tapioca. The values for tapioca were calculated by difference. The digestibility coefficients of dry (DM) and organic matter (OM), crude protein (CP) and neutral detergent fiber (NDF) of tapioca were 78.8, 83.5, −32.8 and −8.1%, respectively, indicating erosion of endogenic protein by the tapioca. The calculated metabolizable energy value of tapioca was 12.80 MJ/kg DM. There were no significant differences in the performance of the animals in the feeding trials when up to 40% of the grain was replaced by tapioca, except for a small increase in DM intake. When SBM was the sole source of supplemental protein, the replacement of 20 and 40% of the grains by tapioca led to a reduced efficiency, of energy conversion into live weight, by 13 and 10%, respectively. Whereas when PL was used for the same purpose the efficiency of energy conversion was about 2% lower but the cost of feed per kg live weight was reduced by 14%. It was concluded that the combination of tapioca and PL in growing-fattening diets is feasible and has no ill effects.