Feeding Value of Sweet Potato and Cassava to Growing Pigs

Abstract

Sweet potato (SP) roots and cassava tubers provide an important feed resource for smallholder farming of pigs in many countries where grain-based feeds are less available. Root and tuber provide digestible starch energy and lower protein however dietary fibre may reduce the digestibility of nutrients and N retention in growing pigs when fed together with protein containing ingredients. Inclusion of SP vine and foliage in daily diets fed to pigs provides an additional source of N, amino acids and dietary fibre. Furthermore, where smallholder producers exploit either commercial (CG) or mixed genotype (MG) pigs their specific nutrient requirements should be determined in order to provide cost-efficient feeding strategies. A series of seven metabolic trials and two growth trials tested the nutrient utilization and growth performance of CG (Landrace × Large White × Duroc) and Papua New Guinean MG pigs fed blended SP or cassava diets. Seven metabolic trials were all conducted in 4×4 Latin Square design using SP or cassava prepared as boiled, ensiled or milled feed, blended with complementary protein concentrates (wheat-based) into nine test diets, with each set of three diets compared against a wheat-based standard feed, using four CG or MG growing pigs (25-30 kg BW) fed to satisfaction over four 8-d periods. One station-based growth trial was conducted in a replicated 4×4 Latin Square design using 16 MG entire-male (8) and female (8) growing pigs (25 kg BW) on restricted feeding of one of two blended SP diets or one of two wheat-based pellet diets over four 10-d periods. One farm-based growth trial was conducted in a 2×6×8 Randomized Complete Block design using 96 MG castrate-male (47) and female (49) growing pigs (21 kg BW) on restricted feeding of either a blended SP root diet or wheat-based pellet diet over 90-d’s. CG pigs were obtained from a large scale commercial piggery and MG pigs were obtained from a local smallholder piggery in PNG. Nutrient utilization was high but N balance and growth performance of pigs varied when fed the prepared forms of root-based and wheat-based diets; between marginally different body weights, and apparently influenced by dietary exposure and genotype. Fibre digestibility in MG pigs was improved compared to CG pigs, N retained from different diets was influenced by the root sources and prepadiets, and it is likely that the protein and amino acid requirements are substantially lower for MG growing pigs. Evaluation of nutrition for sows, weaners and finishers and study of the effect of fermentable carbohydrates on gut physiology and health in MG pigs were recommended