Gross and true ileal digestible amino acid contents of several animal body proteins and their hydrolysates

• The study was based on seven protein hydrolysates from ovine and bovine sources.
• The hydrolysates were highly digestible sources of dietary amino acids (AA).
• True ileal AA digestibility differed among the seven protein hydrolysates.
• The relative digestible AA pattern differed considerably across protein hydrolysates.
• The hydrolysates are suitable for formulating diets specific to end-user requirements.

Amino acid compositions of ovine muscle, ovine myofibrillar protein, ovine spleen, ovine liver, bovine blood plasma, bovine blood globulins and bovine serum albumin and the amino acid compositions and in vivo (laboratory rat) true ileal amino acid digestibilities of hydrolysates (sequential hydrolysis with Neutrase, Alcalase and Flavourzyme) of these protein sources were determined. True ileal amino acid digestibility differed (P < 0.05) among the seven protein hydrolysates. The ovine myofibrillar protein and liver hydrolysates were the most digestible, with a mean true ileal digestibility across all amino acids of 99%. The least digestible protein hydrolysate was bovine serum albumin with a comparable mean true ileal digestibility of 93%. When the digestible amino acid contents were expressed as proportions relative to lysine, considerable differences, across the diverse protein sources, were found in the pattern of predicted absorbed amino acids.