The Effect of Ensiling on the Starch Digestibility Rate of Rehydrated Grain Silages in Pigs Depends on the Hardness of the Maize Hybrid

The aim of the present study was to determine the in vitro starch digestibility kinetics of rehydrated maize grain silages in pigs and to investigate the relationship between the in vitro starch digestibility rate and the physical properties of the mature grain. Grains of seven commercial maize hybrids were harvested at physiological maturity, rehydrated, and ensiled with a commercial inoculant during different ensiling periods (0, 21, and 95 days) in five replicates using a completely randomized design. The starch digestibility rate was determined using first-order kinetics following an in vitro digestibility procedure mimicking the stomach and small intestine of pigs. The tested hybrids differed in their physical properties (test weight, kernel size, and density and hardness), digestion coefficients, and starch digestibility rate (p < 0.05). The starch digestibility rate increased with an increasing ensiling period, with average values of 0.588, 1.013, and 1.179 1/h for 0, 21, and 95 days of ensiling period, respectively. However, the effect of ensiling was more pronounced in hybrids with higher grain hardness, reaching a rate of 1.272 1/h in hybrids with higher grain hardness compared to 1.110 1/h in hybrids with lower grain hardness. In conclusion, ensiling results in higher availability of starch to digestive enzymes, and the duration of ensiling and hardness of the maize hybrid should be considered when formulating the pig diet.