Vegetative growth response and in vitro evaluation of three multipurpose fodder tree leaves and shrubs as potential feeds for farm animals

In a completely randomized design, the vegetative growth and nutritive value of three tree leaves Tectona grandis, Gmelina arborea, and Acacia mangium compared to berseem (Trifolium alexandrinum) hay as a standard high-quality roughage for ruminants were studied. Growth, chemical composition, in vitro gas production (GP), and fermentation characteristics for 48 h of incubation were measured. Results of measured growth parameters showed that the highest mean value of total height, stem base diameter, crown width, shoot fresh weight, and shoot dry weight were observed in Gmelina arborea, Tectona grandis, and Acacia mangium, respectively. Gmelina arborea had higher (P < 0.05) concentrations (%) crude protein (CP) and lower acid detergent fiber (ADF) compared to berseem hay. The lowest (P < 0.05) CP was observed with Tectona grandis; however, it had more (P < 0.01) neutral detergent fiber (NDF) compared to the berseem hay. All tree leaves had higher (P < 0.05) concentrations (%) of total phenolics, and total tannins compared to the berseem hay. Furthermore, Acacia mangium had the lowest GP (P < 0.01) GP (mL/g DM) and the rate (h) of GP (P < 0.01), while had the highest (P < 0.05) lag of GP (h) compared to berseem hay. Acacia mangium showed the lowest methane production (mL/g DM) and the highest methane production expressed as mL/g degraded DM (dDM), with no significant differences between Gmelina arborea, Tectona grandis, and berseem hay. At the same time, Tectona grandis showed the highest (P < 0.05) total (mM) and individual (%) short chain fatty acids concentrations compared to berseem hay. Acacia mangium showed the lowest (P < 0.01) truly degraded DM and organic matter (mg/g incubated) and protozoal count (P < 0.05) (10(5)/mL). Also, Acacia mangium had lower (P < 0.05) ammonia-N concentration (mg/dL), metabolizable energy (MJ/kg DM), and microbial protein production (mg/g DM). Overall, Tectona grandis and Gmelina arborea are more recommended than Acacia mangium due to their higher rumen fermentation characteristics and nutrient degradability; however, Acacia mangium has an importance from an environmental view as it had lower methane production compared to other plants.