A. Donkoh et al., COMPARISON OF METHODS TO DETERMINE THE ENDOGENOUS AMINO-ACID FLOW AT THE TERMINAL ILEUM OF THE GROWING RAT, Journal of the Science of Food and Agriculture, 67(3), 1995, pp. 359-366
The aim was to compare a recently developed peptide alimentation metho
d and the protein-free and regression methods for determining endogeno
us ileal nitrogen (N) and amino acid excretion in the rat, and to appl
y the endogenous loss estimates to determine the true ileal digestibil
ity of a meat and bone meal (MBM). Preliminary investigations determin
ed the effect of the time of sampling of digesta after a meal (slaught
er method) for rats given a protein-free or an enzymically hydrolysed
casein (EHC) based diet, on ileal digesta and endogenous N excretion.
There was a significant (P < 0.05) effect of the time of sampling on t
he amount of digesta collected and the endogenous N excretion for both
the EHC and protein-free fed rats. The amount of digesta collected fr
om the terminal 20 cm of ileum and the endogenous N excretion for both
the EHC and protein-free fed rats were greatest and least variable at
3 h post-feeding. In the main study, endogenous ileal amino acid excr
etions were determined in the growing rat fed an EHC-based diet (n = 6
) and with subsequent treatment of the digesta using ultrafiltration o
r in six rats given a protein-free diet or by extrapolation from data
for 30 animals given five diets which contained graded levels of MBM a
s the sole protein source. For the EHC treatment, the ileal digesta pr
ecipitate plus retentate was used to determine the endogenous flows. T
he ultrafiltration step excludes unabsorbed dietary amino acids from t
he measure of endogenous loss. Chromic oxide was the reference marker
in all diets. The endogenous N flows determined by the protein-free an
d regression methods were similar but both significantly (P < 0.01) lo
wer than those for rats fed the EHC-based diet. The mean endogenous il
eal N flows determined by the peptide alimentation method, the protein
-free and regression approaches were 1866, 1103 and 1019 mu g g(-1) fr
eeze dry matter intake, respectively. The endogenous amino acid flows
at the terminal ileum were lower when determined using the traditional
protein-free or regression methods. The true ileal digestibility coef
ficients for MBM were considerably higher based on the EHC versus prot
ein-free endogenous flows.