Optimizing Rice Straw Nutritive Value and Mineral Content Through Associative Effects of Urea-Lime-Molasses Pre-treatment

Abstract Rice straw pretreatment is an innovative strategy aimed at enhancing the bioavailability of inherent nutrients and supplementing those that are deficient, thereby converting rice straw into a nutritionally enriched feed resource for the livestock sector. This study evaluates a novel pretreatment strategy combining urea, lime, and molasses to improve the nutritional quality, mineral content, and physical properties of rice straw. 27 treatment combinations based on a 3×3×3 factorial design comprising three levels each of urea (0%, 3%, 4% w/w), lime (0%, 2%, 3% w/w), and molasses (0%, 2%, 4% w/w), under controlled ensiling conditions for 21 days. Results indicated that treatment combinations of urea (3% & 4%) with lime (2% & 3%) and molasses (2% & 4%) displayed high-quality straw with a brownish-yellow color, fragrant aroma, soft texture, and no mold. 4% urea treatment increased (P<0.001) crude protein from 3.94% to 7.37% while lime showed no significant effect on protein levels. Urea and lime treatments reduced (P<0.001) fiber fractions—NDF, ADF, and ADL—by 5.31, 2.96, and 2.01 units, respectively with 4% urea, and 5.61, 3.16, and 2.04 units, respectively with 3% lime. The 3% lime treatment increased (P<0.05) calcium content from 0.63% to 2.27%. Molasses (2% and 4%) significantly enhanced mineral content (P<0.001). Microscopic visualization revealed structural loosening of the straw matrix in pretreated samples. Overall, the synergistic use of 4% urea, 3% lime, and 2% molasses offers a sustainable solution for converting rice straw into a nutrient-enriched ruminant feed, potentially reducing feed costs, addressing feed scarcity, and mitigating environmental concerns.