Ph D Thesis Amelie Deglaire - TEL

3.2.2. The growing pig
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With a physiology and a metabolism that are closer to those of the human, the growing
pig has been extensively used for studying human protein metabolism (Bergen, 2007) and
has been proposed as a better model for protein digestion studies (Moughan et al., 1992a;
Moughan et al., 1994; Darragh & Hodgkinson, 2000; Moughan, 2005). Also, the pig
offers the advantage of allowing continuous in vivo ileal collection after surgical
preparations, unlike the rat, from which digesta are collected after euthanasia at a certain
time post meal (Moughan et al., 1994).
At the faecal level, Darragh & Moughan (1995) reported good agreement for apparent N
and AA digestibility between piglets and infants fed milk formula, with N digestibility
values of 97.5 and 94.5%, respectively. A similar observation was made by Forsum et al.
(1981). To our knowledge, few studies have compared the true ileal digestibility of
protein between pigs and humans. Rowan et al. (1994) reported true digestibility
coefficients that were similar between ileostomized subjects and ileostomized pigs,
except for threonine, phenylalanine, methionine and cysteine which were significantly
higher (3−8% units) in humans. This is in line with data across independent studies
(although not direct evidence), showing good agreement between pig and human true
ileal N and AA digestibility values (for soya protein or casein), as reviewed previously
(Fuller & Tomé, 2005). As reported for the growing rat, AA compositions of endogenous
ileal protein losses were similar between the growing pig and the adult human (Table 5),
except for proline for which the contribution was three times higher in pigs.
Although the pig is also a fast-growing animal, the AA scoring pattern is closer between
the growing pig and the adult human than between the growing rat and the adult human
(Table 3). Gut fractional protein synthesis rates were reported to be in the same range,
with pig values of 43 to 51% per day (Simon et al., 1978; Simon et al., 1982) and human
values of 22 to 50% per day (Waterlow, 2006a).
Overall, direct evidence to support the growing pig as an animal model for predicting
ileal protein digestibility in humans is scarce.