Environmental impact, quality, and quantity of food products of ruminant origin (especially beef and mutton) are considered major challenges in meeting the nutritional requirements of the growing human population worldwide. Therefore, we conducted this in vitro study to explore the potential of Paulownia leaves silage to reduce the environmental impact of feedlot lamb production and improve ruminal fatty acids (FAs) profile by influencing ruminal biohydrogenation. In the present study, Paulownia leaves silage (PLS) and alfalfa silage (AAS) were mixed in a proportion of 1:0 (Control, PLS 0%), 0.75:0.25 (PLS 25%), 0.5:0.5 (PLS 50%), 0.25:0.75 (PLS 75%) and 0:1 (PLS 100%) on dry matter basis in the lamb diet. The experimental findings demonstrated that 100% replacement of AAS with PLS in the lamb diet significantly improved the ruminal fermentation by increasing the in vitro DM degradability (P<0.01), total volatile fatty acid (P<0.01), and propionate production (P<0.01) while reducing the acetate: propionate (A/P) ratio (P<0.01) and CH4 concentration (mM; L and Q P<0.05) and CH4 production, mM/g DM (L and Q P<0.05). Meanwhile, 100% PLS inclusion in the diet increased the total monounsaturated fatty acids (P<0.05), total unsaturated fatty acids (P<0.01) and total n-3 fatty acids (P<0.05) particularly alpha-linolenic acid (ALA; C18:3 n-3; P<0.05) in the rumen fluid after incubation. Moreover, the total saturated fatty acids concentration was reduced (P<0.01). These findings suggested that PLS could be a climate-friendly and sustainable alternative to AAS in the lamb feedlot diet for quality meat production.
