According to Wood (1987) and Vukmirović (2015), there is a positive correlation between pellet hardness and pellet durability. Consequently, it could be expected that an increase in moisture content of AP, which decreases pellet hardness, could also cause decrease of PDI. Nevertheless, in this research PDI was very high in all pelleting treatments, regardless of moisture content before pelleting. This was probably because low moisture content caused higher friction and pressure in the die holes. This resulted in decrease of distances between particles thus enhancing particle binding by solid-solid interactions (Thomas and van der Poel, 1996; Vukmirović, 2015). On the other hand, higher moisture content of AP provided more bonds between particles due to capillary sorption and caused better compression characteristics of material due to chemical changes of AP components (Thomas and van der Poel, 1996). Consequently, there were no significant differences between PDI values when AP batches with different moisture contents were pelleted.