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 feedstuffs and ls mixed diets. Considerable variation was found in both chemical composition and digestibility among cereals and cereal by-products, 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 protein feedstuffs and oil seed meals, especially for apparent ileal digestibilities of amino acids. However, there was good agreement between the results and those reported in the literature. The digestibilities of nutrients were affected by many factors, including cell wall constituents, the balance of mineral and trace elements and anti-nutritional factors. Faecal digestibility was higher than ileal digestibility. In general, the differences between apparent faecal digestibilities were smaller than for apparent ideal digestibilities. This indicates that the modifying action of microflora in the large intestine is irregular, therefore the digestibility measured at the end of the ileum is more reliable. However, the high ileal digestibility of cell wall constituents indicates that the influence of the microflora begins before the end of the ileum, and other methods such as isotope dilution techniques should be used to more accurately determine digestion and absorption.