The effect of increasing levels of fish· meal on true lysine availability in intact and caecectomized White Leghorn roosters.

Protein-free diets containing increasing levels (0, 20, 40, 60, 80, and 99%) of normal and heat-damaged fish-meal were force-fed to intact and caecectomized White Leghorn roosters. True lysine availability for the normal fish-meal amounted to 92,9% and for the heat-damaged fish-meal to 52,3%. No difference in true lysine availability value was found between the various levels of fish-meal intake. Caecectomy had a significant effect on true lysine availability of heat-damaged fish-meal – lower values being obtained than with intact roosters (41,9% vs. 52,3%). Lysine availability according to a chick growth assay on the normal fish-meal corresponded fairly well with the rooster assay, the value for the heat-damaged fish-meal, however, was even lower than the value found with caecectomized roosters viz, 34,9 vs. 41,9%. Using chromic oxide as indicator to calculate lysine availability produced values which corresponded well with the total collection method. However, at high levels of fish-meal, the chromic oxide method overestimated lysine availability. The DSQ method for TME determinations was also tested for its applicability to determine amino acid availability. The values obtained for lysine corresponded very well to those obtained with the force-feeding technique.