EFFECTS OF GRINDING, PELLETING AND EXPANDING ON NUTRITIVE-VALUE OF BARLEY IN PIG DIETS

Nutrient digestibility and protein utilization responses of growing pigs to different processes of barley were evaluated. The assayed treatments of barley were grinding methods: hammer milling (HM) and rolling (RM), pelleting (HP, RP), expanding (HE, RE) and their combination (HEP, REP). The study comprised a 8 x 8 Latin square designed digestibility and nitrogen balance trial with a 2 x 2 x 2 factorial arrangement of treatments. The average grist size of HM barley was smaller and wider than that of RM. Pelleting and expanding reduced the grist size and made the distribution wider compared to untreated ones. HM compared to RM achieved improved pellet quality, but expanding had no effect on pellet durability. Only small differences were found in the proximate composition or sugar content indicating a gelatinization degree of differently processed barleys. Grinding method had no effect on organic matter (OM) digestibility, whereas RM improved protein (CP) digestibility (P<0.001) but led to lower ether extract (EE) digestibility (P<0.001). Pelleting significantly improved digestibility of all barley constituents (P<0.01, 0.001), the magnitude being 0.02 compared to meal form barley. A significant interaction between the grinding method and pelleting was noticed in CP (P<0.05) and EE (P<0.001) digestibility. Except for the digestibility of crude fibre (P<0.001), there were no significant differences between the treatments in response to the expanding process of barley. Significant interactions in digestibilities were found between grinding methods and expanding. RM compared to HM achieved significantly higher N-retention (P<0.001) and protein utilization (P<0.001) and decreased urinary urea-N excretion (P<0.001). Pelleting significantly improved protein absorption (P<0.001) and tended to decrease urinary-N excretion, but N-retention was unaffected by the physical form of the barley. Expanding had no effect on protein absorption or N-retention, but achieved a small significant improvement in biological value of protein (P<0.01).