Evaluation of various sulphur amino acid to lysine ratio for growing-finishing pigs fed antibiotic-free diets

Abstract

This 10 wk feeding trial was conducted to determine the effect of increasing the standardised ileal digestible (SID) sulphur amino acid to lysine ratio (SAA:Lys) on performance and intestinal health parameters in growing-finishing (50–100 kg) pigs fed antibiotic-free diets. A total of 96 pigs [(Landrace × Yorkshire) × Duroc] with an average initial body weight (BW) of 52.2 ± 2.32 kg were randomly assigned to 4 dietary treatments each with 6 replicates (4 pigs per pen, 2 females and 2 males). The dietary treatments were 4 graded levels of SID SAA to Lys ratios (0.57, 0.67, 0.70 and 0.73). During the phase 1 (50–75 kg), pigs fed diets with increasing dietary SID SAA:Lys tended to improve the ADG (linear, p = .07) and G:F (linear, p = .06). During the phase 2 (75–100 kg), increasing SID SAA:Lys ratio had a tendency (linear, p = .08) to improve the ADG and G:F. Furthermore, the villus-to-crypt ratio of duodenum were linearly increased (p < .05) by increasing SID SAA:Lys at the end of the experiment. Moreover, increasing SID SAA:Lys ratio linearly improved (p < .05) the ratio of faecal Lactobacillus:Escherichia coli in both phase 1 and phase 2. There was a linear decrease (p < .05) in ammonia when pigs were fed diets with increased SID ratio of SAA:Lys in both phase 1 and phase 2. In conclusion, increasing the dietary SID SAA:Lys provided beneficial effect on gut health of growing-finishing pigs fed antibiotic-free diets and showed partial positive effect in growth performance.