Technical Abstract: Rendered proteins are well suited for animal nutrition applications, but due to their insolubility, inhomogeneity and the presence of non-protein substances, they are difficult to utilize in other applications. In an attempt to overcome these obstacles to utilization, three types of rendered proteins, meat and bone meal (MBM), feather meal (FM) and blood meal (BM), were partially defatted and then hydrolyzed to varying extents using calcium hydroxide or one of three enzymatic treatments, in 4- or 6- liter batches. After centrifugation, filtration and spray drying, these hydrolysates were analyzed for changes in physical and chemical properties that relate to their potential utility. In all cases, the proportion of rendered protein solubilized increased along with hydrolysis duration, although the molar mass distribution of the hydrolysis product only had a weak dependence on hydrolysis duration; the soluble material consisted of very small peptides at all time points. Alkali-hydrolysis was not effective in yielding a product low in ash; although the insoluble ash in MBM and FM appears not to have been carried over into the product, it was replaced by significant amounts of calcium salts; corresponding enzymatically-hydrolyzed batches contained approximately 40% less ash. Alkali-hydrolysis in particular had effects on the amino acid composition of the products, destroying some amino acids and creating others, including the cross-linked amino acids lysinoalanine and lanthionine; enzymatic hydrolysis effects on amino acid composition were different in type and generally lesser in magnitude. It is concluded that hydrolysis is a promising treatment for increasing the non-feed utility of rendered animal proteins.