Enhancing digestion and gut fermentation in pigs: <i>in vitro</i> evaluation of the effects of reconstituted and ensiled sorghum grains

The effect of ensiling sorghum grains harvested at different dates on pig nutrient digestibility and fermentability was evaluated using <i>in vitro</i> approaches. A sorghum crop was divided following a randomised complete block design and distributed in 3 treatments: 1) grain harvested 113 d after sowing (40% moisture) and ensiled for 180 d (high moisture, HMG), 2) grain harvested 159 d after sowing (15% moisture), rehydrated to 40% moisture and ensiled for 180 d (reconstituted, REC), and 3) sorghum grain harvested 159 d after sowing (15% moisture) and stored dry (dry, DG). Starch content was lower in ensiled grains (HMG and REC) (<i>p</i> = 0.019), and lower for HMG (<i>p</i> = 0.043). The resistant starch fraction was lower (<i>p</i> < 0.001), and the predicted glycaemic index was higher (<i>p</i> = 0.029) in ensiled grains. <i>In vitro</i> DM, OM and starch digestibility were greater in ensiled grains (<i>p</i> < 0.001 for all parameters). Ensiled grains had lower <i>in vitro</i> gas production [ml/g DM] (<i>p</i> = 0.002), but the rate of gas production [ml/h] was higher (<i>p</i> = 0.025). Finally, ensiled grains had lower butyrate and higher branched-chain fatty acids concentration [mol/L] (<i>p</i> < 0.001 and <i>p</i> < 0.003, respectively). The ensiling process improved <i>in vitro</i> digestibility and changed fermentation parameters and short-chain fatty acids profile, regardless of DM at harvest.