NUTRITIVE-VALUE OF FEEDSTUFFS AND DIETS FOR PIGS .1. CHEMICAL-COMPOSITION, APPARENT ILEAL AND FECAL DIGESTIBILITIES

The chemical composition, including amino acid content, and ileal and faecal digestibility was determined for 39 batches of 38 different fee dstuffs and ls mixed diets. Considerable variation was found in both c hemical composition and digestibility among cereals and cereal by-prod ucts, legumes, animal protein feedstuffs, oil seed meals, protein and mineral concentrates and mixed diets. Within the different classes of feedstuffs and diets, variation was small for mixed diets and protein and mineral concentrates. A large variation was found for animal prote in feedstuffs and oil seed meals, especially for apparent ileal digest ibilities of amino acids. However, there was good agreement between th e results and those reported in the literature. The digestibilities of nutrients were affected by many factors, including cell wall constitu ents, the balance of mineral and trace elements and anti-nutritional f actors. Faecal digestibility was higher than ileal digestibility. In g eneral, the differences between apparent faecal digestibilities were s maller than for apparent ideal digestibilities. This indicates that th e modifying action of microflora in the large intestine is irregular, therefore the digestibility measured at the end of the ileum is more r eliable. However, the high ileal digestibility of cell wall constituen ts indicates that the influence of the microflora begins before the en d of the ileum, and other methods such as isotope dilution techniques should be used to more accurately determine digestion and absorption.