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Effect of surplus L-Ile plus L-Val in a wheat-based diet with excess Leu on performance and serum concentration of amino acids of growing pigs
A dietary Leu excess can reduce feed intake and performance of pigs. The objective was to evaluate the effect of excess dietary supply of Leu alone or together with Ile and Val on pig growth performance and serum concentrations (SC) of AA. A 21-d experiment was conducted using 24 crossbred pigs (Large White × Duroc × Landrace; initial BW of 31.8 ±1.2 kg) with 8 pig replicates (4 barrows and 4 gilts) per treatment. A basal diet was formulated based on wheat, cornstarch and AA (L-Lys.HCl, L-Thr, DL-Met, L-Trp, L-Leu, L-Ile, L-His, and L-Val) to meet requirement of Lys [0.90% standardized ileal digestible (SID) Lys] and other AA were balanced to meet the ideal protein ratio. The ratios of SID Ile, Leu and Val to Lys in the basal diet were 58, 100, and 73%, respectively. L-Leu (0.43%) alone or together with L-Ile (0.20%) and L-Val (0.35%) were added to the basal diet replacing cornstarch to create a Leu-excess diet and a branched-chain AA (BCAA)-excess diet, respectively. To avoid the confounding effect of excess Leu on feed intake, pigs were fed semi-restricted on average at 1.7 kg/d. The ADG and FCR of pigs fed the basal, excess Leu or excess BCAA were 682, 685, 730 g/d, and 2.33, 2.39, 2.25, respectively. Excess Leu did not affect ADG or FCR (P>0.10). However, excess BCAA increased ADG (P < 0.05) compared with the basal or excess Leu diet and tended to have a better FCR than those fed the excess Leu (P=0.05). Blood samples were collected from all pigs 2.5 h post-prandial on d 21 via jugular vein venipuncture. Excess Leu decreased SC of Ile and Val (P < 0.05). Excess BCAA increased SC of Ile and Val but decreased SC of Leu (P<0.05) compared with the Leu diet. The SC of Ile and Val were not different (P>0.10) among pigs fed the basal or excess BCAA diet, but SC of Leu was lower (P<0.05) in pigs fed the excess BCAA diet. The SC of the other AA were not affected (P>0.10) by the treatments. These data suggest that additional supplementation of Ile and Val to a high Leu diet may ameliorate the growth-depressing effect in growing pigs.
Keywords: Pigs, Isoleucine, Valine