Climate change, feed shortages, and rising production costs highlight the need for alternative and sustainable forages for ruminants. This study aimed to evaluate the nutritional composition, in vitro ruminal fermentation, and methane emissions of Urtica dioica ecotypes originating from contrasting bioclimatic zones in Tunisia. Aerial parts of Urtica dioica were harvested at the early flowering stage from arid, semi-arid, and sub-humid regions. Samples were subjected to chemical composition in vitro ruminal fermentation to determine dry matter degradability (DMD), neutral detergent fiber degradability (NDFD), metabolizable energy (ME), and methane production. The results demonstrate that Urtica dioica is a promising protein-rich forage, with a stable crude protein content across ecotypes (18.58–20.97% of dry matter). In contrast, NDFD, DMD, ME, and methane emissions varied significantly according to origin. The arid ecotype, characterized by the highest fiber, ether extract, and polyphenol content, exhibited the lowest DMD (53% vs. 61% and 60%), NDFD (45% vs. 55% and 56%), and ME (7.2 vs. 8.6 and 9.0 MJ/kg dry matter) but produced the lowest methane emissions (38.8 vs. 53.2 and 74.2 mL CH₄/kg DMD) compared with the semi-arid and sub-humid ecotypes. The semi-arid and sub-humid ecotypes had comparable DMD, NDFD, and ME values; however, methane emissions were higher in the sub-humid ecotype. Overall, the semi-arid ecotype provided the most favorable balance between nutritive quality and environmental sustainability. These findings highlight the critical role of ecological origin in determining the feeding value and greenhouse gas footprint of Urtica dioica, providing a scientific basis for its potential use as a sustainable forage in ruminant feeding systems.

Rising feed costs and the need for more sustainable livestock production have increased interest in co-products as alternative feed resources for rabbits. However, their nutritional value may be underestimated when evaluated only through pre-cecal enzymatic digestion, without considering cecal degradation. This study comparatively characterized pea hulls, artichoke bracts, date flesh, and date pits (three independent sources each, n = 3) and evaluated their nutritional potential using a sequential in vitro procedure combining pre-cecal enzymatic digestion with cecal degradation. Date flesh, characterized by high non-fibrous carbohydrate and low fiber, showed the highest pre-cecal enzymatic dry matter and organic matter digestibility (89.44% and 89.58%, respectively), with minimal additional contribution from cecal degradation. Pea hulls contained the highest crude protein (24.97% of dry matter) and showed high additional degradation of structural carbohydrates during the cecal phase, reaching cumulative neutral detergent fiber and acid detergent fiber digestibility (47.18% and 41.90%, respectively). Artichoke bracts showed moderate pre-cecal enzymatic digestibility and substantial additional utilization during cecal degradation. Date pits had the highest fiber, lignin, and tannin concentrations and the lowest pre-cecal enzymatic digestibility, although cecal degradation partially improved their nutrient utilization. Overall, these in vitro results suggest that cecal degradation can contribute substantially to the digestibility of residual structural carbohydrates in fiber co-products.