Enhancing digestion and gut fermentation in pigs: in vitro 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 in vitro 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) (p = 0.019), and lower for HMG (p = 0.043). The resistant starch fraction was lower (p < 0.001), and the predicted glycaemic index was higher (p = 0.029) in ensiled grains. In vitro DM, OM and starch digestibility were greater in ensiled grains (p < 0.001 for all parameters). Ensiled grains had lower in vitro gas production [ml/g DM] (p = 0.002), but the rate of gas production [ml/h] was higher (p = 0.025). Finally, ensiled grains had lower butyrate and higher branched-chain fatty acids concentration [mol/L] (p < 0.001 and p < 0.003, respectively). The ensiling process improved in vitro digestibility and changed fermentation parameters and short-chain fatty acids profile, regardless of DM at harvest.