Effect of hydrolysis time on the determination of the amino acid composition of diet, ileal digesta, and feces samples and on the determination of dietary amino acid digestibility coefficients

Abstract

A study was undertaken to determine the effect of hydrolysis time during amino acid analysis on individual amino acid yields from samples of a mixed diet, pig ileal digesta, and feces. Representative feed, digesta, and feces samples were hydrolyzed in duplicate in 6 M HC1 in sealed evacuated tubes for 16, 24, 48, and 72 h, respectively, and then analyzed for their yields of alanine, arginine, aspartate, glutamate, glycine, histidine, isoleucine, leucine, lysine, phenylalanine, proline, serine, threonine, tyrosine, and valine. There was a significant (P < 0.05) curvilinear effect of hydrolysis time on the yields of all amino acids except tyrosine. The changes in isoleucine, lysine, and serine yields with hydrolysis time were parallel for the three types of samples, but for the other amino acids (except tyrosine) there were significant (P < 0.05) hydrolysis time-source interactions. This would introduce error into the calculation of amino acid digestibility coefficients if samples were only hydrolyzed for a standard time.To minimize the error due to incomplete hydrolysis or partial loss of amino acids, correction factors for each type of sample were calculated and can be applied to other samples.

Amino acid availability: aspects of chemical analysis and bioassay methodology

“…The study of Rowan et al (1992a) demonstrates that this is not so. Rowan et al (1992a) addressed the effect of hydrolysis time during amino acid analysis on individual amino acid yields from samples of a mixed diet, ileal digesta and faeces. Food, digesta and faeces samples were hydrolysed in duplicate in 6 M-HCl in sealed evacuated tubes for 16, 24, 48 and 72 h, and then analysed for their yields of alanine, arginine, aspartate, glutamate, glycine, histidine, isoleucine, leucine, lysine, phenylalanine, proline, serine, threonine, tyrosine and valine.…”

Sequential hydrolysis of swine carcass samples and determination of amino acid concentrations using pre-column derivatization with phenyl isothiocyanate

“…11 Also, it has been established that valine and isoleucine are released slowly during hydrolysis, while serine and threonine are degraded prior to 24 h hydrolysis. 4,6,12 In the present study, amino acids were greatly released from 2 to 6 h hydrolysis, and valine and isoleucine were not maximized until the ®nal hydrolysis time (66 h). Also, serine and threonine were maximized at hydrolysis times less than 24 h. However, besides serine and threonine, glycine, alanine, arginine and proline also achieved maximum values prior to 24 h hydrolysis.…”

“…Also, serine and threonine were maximized at hydrolysis times less than 24 h. However, besides serine and threonine, glycine, alanine, arginine and proline also achieved maximum values prior to 24 h hydrolysis. Previous research 6 has indicated that glycine and arginine were maximized at hydrolysis times prior to 24 h, but alanine and proline were maximized at 24 h. However, the study dealt with a diet for growing pigs that contained both plant and animal proteins, and only four hydrolysis times were used. Differences in release and degradation of amino acids from proteins have been attributed to protein source.…”

“…4±6 Hydrolysis time (16 to 72 h) has been shown to affect the release and degradation of amino acids in a diet for growing pigs, and standard hydrolysis conditions rarely provide the maximum AA concentration. 6 Some amino acids require either longer or shorter hydrolysis times to provide the maximum yields. 6 The effect of hydrolysis time on AA concentrations in pig carcass has not been investigated.…”

“…6 Some amino acids require either longer or shorter hydrolysis times to provide the maximum yields. 6 The effect of hydrolysis time on AA concentrations in pig carcass has not been investigated. The purposes of the present study were to determine the effect of hydrolysis time and internal standard on AA concentrations in pig carcass.…”