Ileal and total tract apparent crude protein and amino acid digestibility of ensiled and dried cassava leaves and sweet potato vines in growing pigs

The present study was conducted to determine the ileal and total tract apparent digestibility of crude protein (CP) and amino acids (AA) in ensiled and dried cassava (Manihot esculenta) leaves (CL) and sweet potato (Ipomoea batatas) vines (SPV) as a single ingredient or in a 50:50 mixture of CL + SPV in growing (>60 kg BW) pigs. Coefficients of ileal (CIAD) and total tract (CTTAD) apparent digestibilities of organic matter (OM), CP, AA, crude fibre (CF) and neutral detergent fibre (aNDFom) were determined in growing pigs fed practical diets. The CP in the diets originated mainly from ensiled and dried CL, SPV or CL + SPV with the main energy source originating from ensiled cassava root which provided less than 9% of the dietary CP. The six diets were formulated to contain 120 g CP/kg DM, 13 MJ ME/kg DM and were fed to 60 kg growing pigs in a 6 × 6 Latin square design. Daily intake of OM, CF, aNDFom and ME differed (P<0.001) among diets while for DM and CP a trend was observed. There were significant differences among diets (P<0.05) for the CIAD and CTTAD of DM, OM, CP and CF and in the CTTAD of aNDFom. There were differences (P<0.05) among diets for the CIAD of most AA except methionine + cysteine, glycine, glutamic acid and serine. The CIAD of AA for the ensiled CL, SPV and CL + SPV were in most cases not different from the corresponding CIAD of AA of the dried ingredients. The use of a combination of CL and SPV in diets of growing pigs resulted in higher CIAD for CF and several AA compared to expected values from the individual ingredients. The first and second limiting AA in ensiled and dried CL and SPV were found to be methionine + cysteine and lysine. Cassava leaves and sweat potato vines have the potential to improve protein and amino acid supply in diets for growing pigs especially when combined with ingredients containing high concentrations of the first two limiting amino acids.