Exploring feeding value of oak (Quercus incana) leaves: Nutrient intake and utilization in calves

For evaluating the feeding value of oak leaves as a supplement to wheat straw an in vivo study was conducted involving fifteen male calves (aged 6–9 months, average body weight 84 kg,) distributed randomly into three equal groups. The calves in group 1 (G1) received a maintenance diet of concentrate (C) and wheat straw (WS) as the sole roughage; in group 2 (G2), C, WS and oak leaves (OL) at a ratio of 31:39:30 on dry matter (DM) basis and in group 3 (G3), C, WS and OL at a ratio of 33:45:22. The feeding lasted for 4 weeks and included a metabolism trial of 6 days duration. The DMI (kg/day) increased (41 and 38% in G2 and G3, respectively) with supplementation of oak leaves, being higher in G2 (2.90) followed by G3 (2.82) and G1 (2.05). Digestibility (%) of DM, organic matter and neutral detergent fiber was higher in G2 (51.5, 55.8, 49.0) compared to G1 (43.9, 49.3, 43.7) and G3 (45.4, 50.1, 44.0) contributing to higher ME intake (17%). Increased N utilization efficiency (20.6, 67.7 and 55.1% in G1, G2 and G3, respectively) and microbial protein production (180, 209, 194 g/day) coupled with a decrease in plasma urea level (about 25%) was observed in oak leaf supplemented groups. Supplementation of WS/OL ratio of 44:56 enhanced DMI, digestibility, efficiency of N utilization and body weight gain compared with a WS/OL ratio of 100/0.