Determination of the Effects of Different Levels of Prosopis farcta Fruit Supplementation to Low-Quality Roughages on Organic Matter Digestibility and Methane Formation Using the In Vitro Digestion Method

In arid regions and areas facing forage scarcity, Prosopis species have long been used in ruminant nutrition, yet their full potential remains inadequately assessed. Domesticated ruminants contribute approximately 15% of global methane emissions. Previously, antibiotics were routinely added to ruminant diets to reduce methane-associated energy losses and improve feed efficiency; however, sustainable alternative strategies are now required. In this study, widely used but nutritionally limited wheat straw and maize silage were supplemented with varying levels (2%, 4%, 6%, 8%, and 10%) of Prosopis farcta fruit. Using the in vitro gas production technique and cattle rumen fluid, parameters including total gas production, methane formation, ammonia nitrogen concentration, in vitro organic matter digestibility, and metabolizable energy were evaluated. Each treatment was conducted in quadruplicate under standard laboratory conditions. The lowest methane production was observed in wheat straw at control and 8% inclusion levels, and in maize silage at control, 8%, and 100% supplementation groups. The highest methane production occurred in wheat straw at 2%, 4%, 6%, 10%, and 100% inclusion levels, and in maize silage at 6% and 10% supplementation. In wheat straw, 2% and 6% inclusion levels significantly increased metabolizable energy, although methane production also rose considerably. Conversely, 8% supplementation did not increase metabolizable energy but maintained methane production close to control levels (14,56% vs. 13,87%). In maize silage, 10% inclusion maximised metabolizable energy but caused excessive methane emissions. Inclusion levels of 4–6% in maize silage offer productivity benefits but pose environmental risks, whereas 8% supplementation provides a more sustainable balance.