Harvest age of Urochloa hybrids regarding yield, chemical composition, and in vitro biogas production

Abstract

Objective: To evaluate the chemical composition, fermentation, and in vitro biogas production of the Cayman and Cobra cultivars, at different cutting ages.
 Design/Methodology/Approach: Dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose (HEM), and cellulose (CEL) were determined at 28, 35, 42, and 49 cutting days. In vitro dry matter degradation (IVDMD), pH, and concentration of volatile fatty acids (VFA) were determined during fermentation. The biogas volume was estimated at 6, 12, 24, 48, and 72 hours; the volume of methane (CH4) and carbon dioxide (CO2) in the Cobra and Cayman forages was determined at 72 hours. A completely randomized design was used for the experiment.
 Results: There were no differences (P>0.05) in DM production during the different cutting ages. CP was higher (P<0.05) in both cultivars, at 28 and 35 days after the cutting. The NDF, ADF, HEM, and CEL percentages were different in both cultivars. IVDMD was higher (P<0.05) between day 28 and day 42. Finally, CH4 production was lower (P<0.05) at 28 and 35 days after the cutting.
 Study Limitations/Implications: The chemical composition of pastures is influenced by climate and, therefore, further analysis must be carried out during different periods or seasons of the year.
 Findings/Conclusions: The optimal cutting age of the Cobra and Cayman cultivars under drought conditions is between day 28 and day 35 of regrowth. During that period, they have the best chemical and fermentation characteristics.