Evaluation of feedstuffs quality for pigs in Thailand 1. Development in studies on pig diet digestibility

Three barrows and three gilts from Largewhite X (Landrace X Duroc) herd of the Pig Research Farm, Ching Mai University with an average body weight of 50 kg were fitted with terminal ileal T-shaped cannulae made from silicone rubber. A protein free diet was formulated for the determination of the composition and amount of endogenous nitrogen. A basal diet was formulated from corn-soybean meal for the study of the ileal and faecal digestibilities. The T-test procedure was used to compare differences between ileal and faecal digestibilities. Crude protein and amino acid composition of the endogenous substances except for lysine, methionine, valine, glutamic acid, aspartic acid and tyrosine, were generally higher in ileal digesta than in the faecal digesta. Only about half of the crude protein and less of glycine and proline were recovered in faeces when compared with ileal digesta (p0.01). The faecal digestibility of the basal diet was significantly higher than ileal digestibilities for dry matter, crude protein, crude fibre (p0.01), threonine, cystine, valine (p0.05) and all of the dispensable amino acids (p0.01) except for alanine (p0.05) and non-significant (p0.05) for tyrosine. The trend was the same for true digestibility. The comparison between apparent and true digestibilities showed that true digestibility always tended to be higher than apparent digestibility both for ileal and faecal digestibilities. Crude protein and amino acids in endogenous substances were generally higher in ileal digesta than in faecal digesta, especially crude protein, glycine and proline, whereas, net synthesis of lysine occurred in the large intestine. For the basal diet, the use of apparent and true faecal digestibility values overestimate digestibility in the small intestine by 5 and 1 percent for crude protein and by 5 and 4 percent for threonine, respectively. The underestimation found when digestibility was measured from faeces was about 1 percent for lysine and methionine in both apparent and true digestibilities. Therefore, ileal digestibility values are to be preferred for use in ration formulations for pigs.