Comparison of the Ileal Digestibility of Amino Acids in Meat and Bone Meal for Broiler Chickens and Growing Rats

The apparent ileal amino acid digestibility in 15 meat and bone samples was compared in growing broiler chickens and growing laboratory rat. The animals were given a diet containing meat and bone meal as the sole source of protein. All diets contained chromic oxide as the indigestible marker to calculate the digestibility estimates. Comparison of digestibility data shows that, for all dispensable amino acids, apparent ileal amino acid digestibility was similar (p>0.05) between broiler chicken and the growing rat. However, the ileal amino acid digestibility was similar (p>0.05) between the two species for only four (histidine, methionine, threonine and valine) of the nine indispensable amino acids. Significant differences (p<0.01 to 0.05) were observed between the estimates in the broiler chicken and the rat for arginine, leucine, lysine, phenylalanine and cystine. Differences approaching statistical significance were observed for isoleucine (p=0.06) and tyrosine (p=0.10). For the amino acids, which differed between the species, the values obtained for broilers were consistently 4 to 7 percentage units lower than those in the rats. The exception was cystine, with digestibility in broilers being 17 percentage units lower than in the rat. The present data do not support the use of the growing rat as a model for growing chickens in the determination of ileal amino acid digestibility.