The objectives of this study were (a) to investigate the effect of body weight (BW) on available energy in fibre-rich diets containing two NDF levels; and (b) to evaluate the effect of fibre type and NDF level on AA digestibility. In Exp. 1, barrows (24 at 33.4 ± 1.1 kg; 24 at 86.8 ± 3.3 kg) were randomly allotted to 4 diets containing a high protein basal (HPB), a low protein basal (LPB), 70% HPB + 30% wheat bran (WB) (HPB-WB) and 70% LPB + 30% sunflower meal (SFM) (LPB-SFM). In Exp. 2, barrows (24 at 33.5 ± 1.8 kg; 24 at 87.0 ± 3.8 kg) were randomly allotted to 4 diets containing no SFM with 12% NDF (SFM0LF), no SFM with 16% NDF (SFM0HF), 24% SFM with 12% NDF (SFM24LF) and 24% SFM with 16% NDF (SFM24HF). In Exp. 3, twelve barrows (35.5 ± 3.4 kg) fitted with T-cannulas were allotted to two 6 × 4 Youden square design with 6 diets (4 same diets as in Exp. 2 and 2 nitrogen-free diets). The concentration of DE, ME and ATTD of GE, CP, NDF and ADF in diets was greater (p < .01) when fed to 90 kg pigs compared with 30 kg pigs. The ME in ingredients was not affected by BW. The ATTD of NDF was negatively correlated with the CF (r = -.98; p < .01), ADF (r = -.99; p < .01) and ADL content (r = -.96; p < .01). The ME of diets was negatively correlated with the ATTD of CF (r = -.98; p < .01). The addition of SFM increased the standardized ileal digestibility (SID) of Met (p < .05). In conclusion, diets rich in fibre had different nutritional values at different pig weight stages. The AA digestibility depends mainly on chemical composition of diets.
Keywords: amino acid; body weight; digestibility; fibre; pigs; sunflower meal.
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