Rosehip Fruit Residue, Tobacco Leaf, Nettle Herb, and Nettle Seed Cake as Potential Ruminant Feeds: Nutritional Value, In Vitro Digestibility, Gas Production and Methane Emissions

This study aimed to evaluate the nutritional composition, in vitro digestibility, in vitro gas production, and methane emissions of four unconventional feed sources: rosehip fruit residue (RFR), tobacco leaf (TBL), nettle herb (NTH), and nettle seed cake (NTC) for potential use in ruminant rations. Feed samples were analysed for their chemical composition and cell wall structural components. In vitro gas production technique (Hohenheim) was conducted to determine fermentation kinetics, organic matter digestibility (OMD), metabolizable energy (ME), and net energy for lactation (NE_L). Daisy Incubator was used to determine in vitro true digestibility (IVTD) of samples. In addition, an infrared methane analyzer was used to estimate methane production. The results indicated that NTC is a protein-rich material (27.91% CP) that can be used as a feed ingredient in animal diets, with potential for reducing methane emissions. Nettle herb and TBL had high crude protein contents (26.75% and 24.24%, respectively), superior digestibility (IVTD 83.74% and 87.67%, respectively), produced higher total gas volumes after 24 hours of incubation (36.46 and 33.01 mL/200 mg DM, respectively), and methane production of 7.45 and 3.56 mL, respectively. These results indicate their potential as valuable protein sources in ruminant feeding. Rosehip fruit residue and NTC recorded lower gas production (14.25 and 15.30 mL/200 mg DM at 24 hours) and methane production (3.29 and 2.06 mL, respectively). These unconventional materials, promising potential as alternative feed sources in animal nutrition, can be used when properly balanced in rations. When combined with traditional roughages and concentrated feeds, they can be used partially, especially in ruminant feeding. Further in vivo studies are recommended to evaluate the effects of these feed sources on feed intake, nutrient utilisation, animal performance, and methane mitigation under practical feeding conditions.