1. A slope-ratio assay was developed to determine the availability of lysine in protein concentrates for chicks, Two protein concentrates were assessed per assay, using three levels of incorporation into the basal diet.2. Availability of lysine, expressed as a proportion of total lysine in five protein concentrates was: cottonseed meal 0·83, fish meal 1·00, meat-and-bone meal 0·86, soya-bean meal 0·93, sunflower meal 1·01.3. The five protein concentrates had previously been assayed for available lysine with slope-ratio assays for pies and rats (Batterham et al. 1979; Batterharn et al. 1981), There was little relationship between the results for chicks and those for pigs and rats. For pigs, availability estimates ranged from 0·43 for cottonseed meal to 0·89 for fish meal. For rats, availability estimates ranged from 0·49 for sunflower meal to 1·04 for fish meal.4. The results for chicks were in closer agreement with values obtained using the Silcock available-lysine assay (Roach et al. 1967) and the direct 1-fluoro-2,4-dinitrobenzene procedure (Carpenter, 1960). By contrast, there was litlle relationship between the chemical tests and results for pigs or rats.
Available Lysine as an Index of Fish Meal Quality