Two experiments were conducted to evaluate the relevance of formulating pig
diets according to apparent ileal digestible amino acid contents. In Exp.
1, six pigs were fitted with post-valvular T-caecum (PVTC) cannula in order
to determine apparent ileal digestibility of crude protein (CP) and amino
acids of soyabean meal (SBM), rapeseed meal (RSM), maize (M), wheat (W) and
barley (B). In Exp. 2, two consecutive balance trials were performed with
four groups of six male pigs (Polish Landrace) of initial body weight of ab
out 28 kg. Pigs were fed according to their metabolic BW with four diets di
ffering in CP levels, formulated on the basis of ileal digestible amino aci
d content, according to Dutch recommendations (Voedenormen landbouwhuisdier
en, Centraal Veevoederbureau, No. 18, Lelystad. The Netherlands, 1995). Two
diets containing low (L-SBM) and high (H-SBM) protein level: 151 and 165 g
/kg, respectively, were composed of soyabean meal, maize and barley, acid t
wo other diets containing also low (L-RSM) and high (H-RSM) protein level:
161 and 175 g/kg, respectively were composed of rapeseed meal and wheat.
In Exp. 1, distinct differences were found between SBM and RSM in their dig
estibilities of CP (77.0 and 59.5%, respectively) and all amino acids. Amon
g the cereals, CP digestibility and that of most amino acids were the highe
st for wheat and the lowest for barley. In Exp. 2, urinary N excretion, exp
ressed in percent of intake, was the highest in pigs fed on diets H-RSM (36
.2%) and L-RSM (37.0%) and was the lowest on diet L-SBM (30.1%). Accordingl
y, N retention was lower (P <0.001) after feeding rapeseed than soyabean me
al diets (on average 47.5 and 52.2%, respectively). Daily N retention range
d from 20.0 g (L-RSM) to 22.9 g (H-SBM), and these values differed at P < 0
.05. Possible factors affecting balance differences are discussed. (C) 1999
Elsevier Science B.V. All rights reserved.