Evaluation of local protein resources for growing pigs in Central Vietnam

 The general objectives of the work presented here were to evaluate processing methods for the preservations of cassava leaves (CL) and sweet potato vines (SPV) for later feeding during feed shortages in Vietnam. In addition, the nutritional value (including hydrogen cyanide (HCN) contents) of stored and processed CL and SPV as ingredients in diets for pigs were studied to determine their optimal use.The impact of different levels of various carbohydrates added to CL on ensiling and chemical properties was investigated (study 1). Inclusion of rice bran or cassava root meal at 5 or 10% (fresh basis),produced good quality silage that can be stored for up to three months. Ensiling reduced the HCN content up to 80% compared to the content in fresh CL. Using ensiled or dry CL and SPV to replace 70%of the crude protein in a practical fish meal based diet commonly used in Vietnam, gave similar performance results and carcass traits of Large White×Mong Caipigs (study 2). However, increasing ensiled CL from variety KM94 from 0 to 20% (in DM) in diets caused a significant decrease in the average daily gain of pigs but resulted in a 9-18% reduction in feed cost (study 3). Studies into the ileal and total tract apparent digestibility of amino acids and crude protein of ensiled and dried CL and SPV showed that these feed ingredients have the potential to improve the supply of amino acids and protein to growing pigs when fed practical diets (study 4). The chemical analyses indicated CL to have a higher crude protein content than SPV and that ensiling slightly decreases the crude protein as well as the amino acids content. Ensiling however, resulted in a higher digestibility of dietary nutrients compared to drying. Thefirst and second limiting amino acids for ensiled and dried CL and SPV for growing pigs were methionine+cysteine and lysine. Mixing ensiled CL and SPV vines may provide additional benefits in terms of amino acid digestibility over feeding these ingredients alone to pigs. Supplementation of diets containing ensiled CL with methionine and lysine showed that the performance of growing pigs can be increased, as well as the economic benefits for farmers (study 5).The work presented shows that CL and SPV are economical alternatives for more traditionally protein source (e.g. fish meal, soybean meal) for pigs in Vietnam. Ensiling appears to be a practical solution to conserve sweet potato vines and cassava leaves and provide a solution for the rainy season when preservation by sun-drying is difficult.