Nutrient Solution and Harvest Age of Hydroponic Maize Fodder: Potential Influence on Chemical Composition, Rumen Digestion and Mitigation of Gas, CH4 and CO2 Emissions in Brahman Bulls

Forage scarcity, especially during dry periods, limits feed availability for livestock systems, affecting the productivity and sustainability of animal production. The aim of this investigation was to determine the effect of three harvest ages (8, 10 and 12 days) and five nutrient solution concentrations (0, 25, 50, 75 and 100%) on the morpho-agronomic performance, chemical composition, digestibility, rumen degradation kinetics and mitigation of gas, CH4 and CO2 emissions of hydroponic maize forage. Digestibility, degradation, and the reduction in total gas, CH4, and CO2 emissions were evaluated using in vitro techniques. A completely randomized design in a factorial arrangement (3 × 5) was used (8, 10 and 12 days of harvest) (0, 25, 50, 75 and 100% nutrient solution). Four Brahman bulls weighing 550 ± 30.5 kg were used, each fitted with a ruminal cannula. The animals were kept in separate pens, where they were fed Megathyrsus maximus and had access to water ad libitum. Biomass production demonstrated significant differences (p < 0.0001) for the effect of harvest age (12 days), concentration (100%), and their interaction. Dry matter, crude protein, neutral detergent fiber, and acid detergent fiber indicated significant differences (p < 0.0001) for the effect of harvest age, concentration, and their interaction. Dry matter digestibility yielded an effect of harvest age (8 days), concentration (75% and 100%), and their interaction (p < 0.0001). Rumen dry matter degradation of the soluble fraction, potential degradation, and effective degradation (0.02, 0.05, and 0.08, respectively) indicated an effect of harvest age, concentration, and their interaction (p < 0.0001). Gas, CH4 and CO2 production had an effect on harvest age (8 days) and fertilization concentration (75% and 100%; p < 0.0001). It can be concluded that at early harvest ages (8–10 days) combined with intermediate to high concentrations of nutrient solution (75–100%), the biomass production and chemical composition, and thus the increase in ruminal digestibility and degradability and therefore the mitigation of CH4 and CO2, of hydroponic maize forage are optimized, making it a feeding strategy for sustainable livestock production.