Camelina straw as an eco-friendly forage alternative for finishing lambs: impacts on performance, rumen function and behavior

The increasing frequency of droughts and water scarcity has intensified interest in drought-tolerant plants and their by-products as sustainable feed alternatives for ruminants. This study assessed the partial replacement of alfalfa hay (AH) with camelina straw (CS) at 120 (CS12) and 240 (CS24) g/kg of DM in diets of Grey Shirazi lambs (n = 24, average body weight = 22.7 ± 1.7 kg). No significant differences were observed in dry matter intake (DMI), final body weight (FBW: 40.4, 38.8, 40.0 kg), average daily gain (ADG: 285, 260, 278 g/d), or feed conversion ratio (FCR: 5.2, 5.3, 5.1) across treatments. Linear reductions occurred in OM and NDFom digestibility (P < 0.05), with no effects on other nutrients. Ruminal pH, NH₃N, and volatile fatty acids (VFAs) profiles were not significantly altered, except for acetate and isovalerate concentrations, which increased linearly. Partial replacement of AH with CS increased ruminating and total chewing times (P < 0.01), due to higher physically effective fiber intake, without altering meal frequency or duration. These results suggest that camelina straw can be used as a partial AH substitute in lamb finishing diets up to 240 g/kg DM without compromising lamb performance, despite modest reductions in fiber digestibility and increased chewing activity. Future studies should explore behavioral and microbial ecological shifts in the rumen to better understand the mechanisms involved.