Influence of Amylopectin and Nitrogen Supplementation on Digestibility and Ruminal Fermentation of Dairy Heifers Based on Diets with High Ratio of Pineapple Waste Silage to Pangola Grass Hay

Four crossbred Holstein heifers were assigned in a 4x4 Latin square design to evaluate the effects of supplementing either amylopectin (AP) or nitrogen (N),and both in mixed diets containing high ratio of pineapple waste silage (PWS) to pangola grass hay (PGH) on feed intake, apparent digestibility and ruminal fermentation. The treatments included: T1) control diet, PGH and concentrate pellet (CT) at ratio of 70:30, T2) PGH, PWS and CT at ratio of 20:50:20 plus 10% cassava chip (CC) as AP source, T3) PGH, PWS and CT at ratio of 20:50:29.5 plus 0.5% urea as N source and T4) PGH, PWS and CT at ratio of 20:50:19.5 plus 10% CC and 0.5% urea. The results indicated that feed intake was similar in all groups (P>0.05) whereas the digestion coefficient and digestible nutrient intake in the control group were lower than those fed mixed diets with PWS and PGH (P<0.05). The supplementation with either AP or N, and both revealed an increase in digestion coefficient of dry matter (DM) and organic matter (OM) (P<0.05), but not affected on digestion coefficients of crude protein (CP) and neutral detergent fiber (NDF) (P>0.05). All supplements improved digestible CP intake in heifers (P<0.05). However, there was no effect on rumen pH and volatile fatty acid concentrations (P>0.05) in all groups. The results suggest that supplementing either AP or N, and both may benefit to improve feed digestion and digestible nutrient intake in dairy heifers when fed diets with high PWS to PGH ratio.