Growth rate of male Bali cattle (Bos javanicus) fed leucaena and rice straw diets with increasing levels of cassava

Context: The planting and use of leucaena (Leucaena leucocephala) to fatten cattle is both practical and profitable for smallholder farmers in West Nusa Tenggara, Indonesia. Currently smallholder farmers feed leucaena as the primary component of a cattle fattening diet. However, the high protein content in leucaena could be more effectively used if combined with a fermentable energy source, such as cassava (Manihot utilissima). Aim: An experiment was conducted to determine the ratio of leucaena to cassava corresponding to largest average daily gain and most efficient feed conversion for gain. Methods: Thirty growing male Bali cattle (Bos javanicus) 18 months of age with an initial live weight of 164 ± 1.8 kg (mean ± s.e.) were allocated to one of six experimental treatments in a randomised block design. Bulls were held in individual stalls and had access to experimental diets and water ad libitum. The diets were 20% rice straw + 80% leucaena hay (A), 20% rice straw + 65% leucaena hay + 15% cassava meal (B), 20% rice straw + 50% leucaena hay + 30% cassava meal (C), 20% rice straw + 35% leucaena hay + 45% cassava meal (D), 20% rice straw + 20% leucaena hay + 60% cassava meal (E) and 20% rice straw + 5% leucaena hay + 75% cassava meal (F). A mineral mix was provided at 1% DM of total diet and urea was added to the cassava meal at 2% DM. In consideration of animal welfare concerns, the trial was concluded on Day 77 due to observations indicating that bulls receiving the highest level of cassava (F) were experiencing significant weight loss. Key results: The optimum level of inclusion of cassava was 29.5% (based on the quadratic response curve) but there was little difference in average daily gain up to 45% inclusion. Feeding a high level of cassava meal (more than 45% of diet) reduced feed intake, average daily gain and income over feed cost. Conclusion: Cassava meal can be successfully and profitably incorporated into leucaena-based rations of Bali bulls for fattening. Implications: Formulating rations with cassava meal and leucaena can be economically beneficial in cattle fattening systems.