Nutrient utilisation in grower pigs fed boiled, ensiled or milled cassava roots blended with a high protein concentrate

Cassava is a major pig feed ingredient used by smallholder farmers in tropical countries where it is grown abundantly. Due to its high starch content cassava roots may replace maize or wheat as the energy component of rations fed to pigs. A metabolic experiment was conducted using a 4 × 4 Latin Square design to determine the apparent total tract digestibility (ATTD) of nutrients, energy and ni- trogen balance of cassava roots prepared by boiling (BR45), ensiling (ER45) or milling into dry meal (MR45). The cassava products (55%DM) were blended with a wheat based protein concentrate (Pig Conc. 1 at 45% DM), and compared with a wheat-based standard feed (STD) offered to (Landrace × Large White) × Duroc grower pigs (28.0 ± 0.8 kg). DM intakes of pigs were higher on the cassava diets (P ER45 > STD > MR45. Growth rate (ADG) and feed efficiency (FCR) on MR45 (1138 g/d and 1.81) were better than on STD (847 g/d and 2.41), whereas ER45 (856 g/d and 2.59) was similar to STD (P > 0.05). BR45 was similar to STD for ADG (919 g/d) but not for feed efficiency (3.12). The ATTD of DM, organic matter (OM), calcium and energy utilisa- tion (%) in pigs fed the cassava diets were higher (P 0.05). N digestibility (77.9% intake) and N utilisation (64% digested) were also sim- ilar (P > 0.05). N retained by pigs on MR45 (25.1 g/d) was lower than on STD (27.6 g/d). However, higher N retained (P < 0.05) on BR45 (32.0 g/d) and ER45 (31.3 g/d) did not result in improved FCR or ADG, suggesting that high DM intake of soluble dietary fibre may have affected N utilisation, even if energy utilisation was increased by hindgut fermentation. Nevertheless, cassava roots blended with the complementary protein concentrate provided improved nutrition for grower pigs. Ensiling cassava roots allows the option of long term storage of fermented feed with potential benefits to gut health. However, growth performance trials are required to refine the nutrient requirements for local crossbred pigs farmed in tropical climates.Michael T. Dom, Workneh K. Ayalew, Philip C. Glatz, Roy N. Kirkwood and Paul E. Hughe