Ileal digestibility of dietary protein in the growing pig and adult human

Abstract

The suitability of the pig as an animal model for predicting protein digestibility in man was evaluated. Healthy adult human subjects (mean body weight 67 kg; n 11) and growing pigs (mean body weight 40 kg; n 15) were fed semi-synthetic mixed meals containing, as a sole source of N, casein (C), hydrolysed casein (HC) or rapeseed isolate (R). There was no prior adaptation to the test meal. Ileal digesta were sampled through a naso-ileal tube (human subjects) or a post-valve T-caecum cannula (pigs) after ingestion of a bolus meal. The protein sources were 15 N-labelled. Amino acid (AA) digestibilities were not determined for R. Ileal apparent N digestibility was markedly lower (14-16 %; P, 0·001) in human subjects than in pigs (C, HC, R). Similarly, most apparent ileal AA digestibilities were lower (8 % on average; P,0·05) in human subjects (C, HC). Ileal true N digestibility was slightly lower (3 -5 %; P,0·001) in human subjects than in pigs (C, HC, R) and most true ileal AA digestibilities were similar (P. 0·05) between the species (C, HC). Exceptions were for phenylalanine, tyrosine, lysine, histidine and aspartic acid for which digestibilities were lower (3 % on average; P, 0·001) in human subjects. A similar ranking of the diets was observed for true ileal N digestibility between species. The inter-species correlation for true ileal digestibility was high for N (r 0·98 over 3 £ 2 data; P¼ 0·11) and AA (r 0·87 over 26 £ 2 data; P,0·0001). Overall, this supports the use of the pig as a model for predicting differences among dietary protein digestibility, especially regarding true ileal N digestibility, in man.

Canola/rapeseed protein-functionality and nutrition

“…According to this study, canola protein (protein content as %N × 6.25 was 93%, protein isolate obtained under very mild conditions) can be placed similar to egg protein that has high biological value because of the high levels of cysteine and methionine; 80% higher than the limiting value for S-AA (39.0 mg/g), and the 1:1 ratio of Met: Cys. Using the same canola protein material as the protein source, Deglaire et al (2009) showed weaning piglet model can produce highly correlated assessment with human testing. Canola protein showed high correlation with true ileal digestibility of nitrogen (r = 0.98, over 3 × 2, P = 0.11) and amino acids (r = 0.87, over 26 × 2 data, P < 0.0001) with the data of human and weaning piglet model studies.…”

The challenge of diabetes in Asia

“…The NPPU of Tomé et al is very well developed in humans and with application to the pig model could very clearly be used to quantify the necessary correction or adjustment factors required to calculate human DIASS values from pig TID protocol studies. In those instances where the existing and welldescribed method in humans has been replicated in the pig, there has been excellent agreement of the values to the TID pig values (Deglaire et al, 2009a).…”

“…Pig true ileal amino acid digestibility and ileal reactive lysine digestibility measures have been thoroughly validated in pig studies and have been shown to be accurate predictors of absorption in this animal. Published studies (based on four protein sources) show close inter-species agreement between growing pigs and the adult human for true ileal amino acid digestibility (Deglaire et al, 2009a;Rowan et al, 1994).…”

“…Research by Deglaire et al (2009a) and Rowan et al (1994) and has shown a high degree of agreement for true ileal amino acid digestibility between the adult human and the growing pig, but this is based on a limited number of foods. In light of this, the 2011 FAO Expert Consultation recommended that more work be conducted to compare true ileal amino acid digestibility values between the human and growing pig using protein sources that are representative of those consumed by human populations, to further validate the pig as a model animal.…”

Endogenous proteins in terminal ileal digesta of adult subjects fed a casein-based diet

“…As a result, alternative methods, which involve the feeding of protein-containing diets, have been developed (9,13,14). Accurate determinations of endogenous total nitrogen and amino acid flows are necessary to allow the determination of true dietary amino acid digestibility coefficients and for the factorial estimation of dietary amino acid requirements (15). Although there have been several published estimates of the endogenous amino acid composition of human ileal digesta (8), to our knowledge, there have been no systematic studies of the endogenous protein composition (ie, sources of endogenous protein) of ileal digesta in humans.…”