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This study was conducted to determine the seasonal variation (two seasonal harvests during winter and spring) in some chemical and biochemical characteristics of Paulownia shan tong leaves. To achieve this, we analyzed the chemical composition in terms of dry matter (DM), organic matter (OM), crude protein (CP), cell-wall content (neutral detergent fiber (NDF)), acid detergent fiber (ADF), acid detergent lignin (ADL), and lipids. The phenolic compounds (PC) and antioxidant activity (AA) of the leaves were also determined. In vitro gas production (GP) and nutrient degradability were evaluated using two ruminal-content donors (sheep and goats). Higher (p < 0.05) antioxidant activities were observed in the winter harvest of P. shan tong, while higher concentrations of OM (90.5%), lipids (3.02%), NDF (69.7%), ADF (54.8%), ADL (35.4%), total flavonoids (0.45 mg catechin equivalents/mg DM), and total phenolics (2.52 mg gallic acid equivalents/mg DM) were observed in the spring harvest. Higher asymptotic GP and rate of GP (p < 0.05) were observed when the leaves were incubated with rumen liquor of goats compared to sheep; however, higher (p < 0.05) lag time of GP and half-time of GP were observed with rumen liquor from sheep. Moreover, higher asymptotic GP, rate of GP, and half-time of GP were observed with the winter harvest of P. shan tong. Higher (p < 0.001) metabolizable energy, OM degradability, and microbial protein supplies were obtained when the leaves were incubated with rumen fluids from goats and from the winter harvest of P. shan tong compared to the spring harvest. In conclusion, based on the chemical composition and the kinetics of in vitro gas production, P. shan tong leaves seem to be characterized by a good nutritive value and could be considered as an alternative feed resource for ruminants.

The aim of this study was to assess the effects of five eucalyptus species (Eucalyptus camaldulensis, E. leucoxylon, E. astringens, E. sideroxylon, and E. lehmannii), harvested in spring, autumn, or winter from two Tunisian arboretums, on in vitro rumen fermentation and methanogenesis. Batch cultures were performed to determine rumen fermentation kinetics and end-product formation after 24 h of incubation. The foliage of the species E. sideroxylon and E. lehmannii showed the greatest digestibility coefficients, whereas E. leucoxylon was the least digestible. Acetate-to-propionate ratio was reduced when E. sideroxylon and E. lehmannii were incubated, and these species were also the most efficient at reducing methane emission. Foliage harvested in winter showed greater digestibility and an increase in the acetate-to-propionate ratio than in other seasons, without an increase in methane emission. Foliage from E. sideroxylon and E. lehmannii showed a potential to decrease enteric methane production without depressing effects on ruminal fermentation. In vivo studies would be necessary to conclusively validate these effects as the first step towards proposing the inclusion of eucalyptus leaves in ruminant diets.

The objective of the study was to evaluate the nutritional value of leaves from fve eucalyptus species (Eucalyptus astringens, E. leucoxylon, E. sideroxylon, E. lehmannii, E. camaldulensis), harvested in Tunisia (two locations) during the autumn, winter, and spring seasons. Chemical composition and digestibility (various in vitro procedures) and in vitro tannin biological activity were determined. The species E. lehmannii had the lowest neutral detergent fber (NDF) and lignin contents (252 and 92 g kg−1 dry matter (DM), respectively) and the highest nonfbrous carbohydrates content (553 g kg−1 DM), while the species E. leucoxylon and E. camaldulensis had the highest NDF concentrations (375 and 356 g kg−1 DM, respectively). Among the seasons, higher levels of NDF and lignin were observed in winter (349 and 129 g kg−1 DM, respectively). The species E. sideroxylon showed the highest gas production with polyethylene glycol addition and thus the highest biological tannin activity. The species E. lehmannii and E. camaldulensis had the highest metabolizable energy concentrations, with 6.20 and 6.07 MJ kg−1 DM, respectively. E. camaldulensis showed the highest (37.9%) and E. lehmannii the lowest (31.9%) organic matter digestibility. Foliage from eucalyptus trees are of limited energy and protein value as an alternative fodder for ruminants, with a substantial variability across species. No remarkable seasonal variations in chemical composition and digestibility of eucalyptus foliage were detected.