The Effects of Maturity and Preservation Method on Nutrient Composition and Digestibility of Master Graze
The objective of experiment two was to evaluate the effects of maturity and harvest preservation method on Master Graze (MG) nutrient composition and digestibility. The MG was harvested on June 28 (Cut 1; 48 days), July 20 (Cut 2; 69 days), and August 12 (Cut 3; 92 days) and samples were then preserved using three different preservation methods (oven-dried hay (HAY), ensiled (SIL), or freeze dried (FD)) at each maturity. The collected samples were then analyzed for organic matter (OM), crude protein (CP), ether extract (EE), acid detergent fiber (ADF), neutral detergent fiber (NDF) and lignin. The OM content was similar for Cut 2 and Cut 3 and both were higher (P < 0.01) than Cut 1 (92.4, 95.4 and 95.0% for cuts 1 to 3, respectively). The NDF content was highest (P < 0.05) with Cut 3 (63.1%) and was least (P < 0.05) with Cut 2 (60.1%). Cut 3 had a higher (P < 0.01) lignin content compared to both Cut 1 and Cut 2 (3.5, 3.4 and 4.1%, respectively). Crude protein content was higher (P < 0.01) for Cut 1 than Cut 2 and Cut 3 (8.0, 6.0, and 6.0%, respectively). The preservation method did not affect the CP or lignin content of the MG. The NDF content was highest (P < 0.01) with HAY (65.8%) and was least (P < 0.01) with FD (58.6%). The digestibility of the MG was measured under in situ conditions using one cow fitted with a rumen cannula. The ground oven-dried hay, ensiled and freeze dried samples were incubated in the rumen for 24 h using the mobile nylon bag techniques. The DM digestibility for Cut 1 and Cut 2 were higher (P < 0.01) than Cut 3 (70.0, 67.0 and 60.3%, respectively). The NDF digestibility was highest for Cut 1 and decreased (P < 0.01) with maturity (58.5, 51.6 and 43.8% for Cuts 1 to 3, respectively). Similarly, the CP digestibility was highest for Cut 1 and also decreased (P < 0.01) with maturity (68.3, 56.1 and 46.5% for Cuts 1 to 3, respectively). The DM and OM digestibility was higher (P < 0.04) with the FD in comparison to both HAY and SIL. Digestibility of NDF was not affected (P > 0.05) by preservation methods, while the CP digestibility was higher (P < 0.03) with the FD (61.6%) than the HAY (51.4%). In conclusion, the nutrient composition and digestibility of the MG were both affected by stage of the maturity and preservation method. The nutritional quality of MG decreased with advanced maturity and the MG digestibility was higher when FD preservation method was used.