The Effect of Different Incubation Periods on the Nutritional Quality and In Vitro Rumen Characteristics of Alkali-Pretreated Rice Straw

Abstract

Urea treatment of straw is a widely established method but because of longer incubation period adoption rate is low. Present study aims to determine minimum incubation period for optimum nutrient enrichment of rice straw. Straw was treated with 4% urea, 3% lime & 2% molasses (w/w) maintaining 40% moisture level, which was anaerobically incubated for eight different incubation periods (2, 5, 7, 10, 14, 18, 21 and 28 days) along with control as untreated rice straw (C) without incubation. Each period had three replicates (9 × 3 = 27samples). After the completion of each incubation period, the straw was analysed for its nutritive value. The results showed significantly (P < 0.05) higher crude protein content and reduced cell wall components (neutral detergent fibre, acid detergent fibre and acid detergent lignin) from 14 days incubation onwards, however, among 18, 21 and 28 days of incubation, it remained non-significant (P > 0.05). Hence, 14- and 18-days incubated samples were taken for in vitro rumen fermentation parameters. The results indicated that dry matter and organic matter digestibility significantly (P < 0.05) greater in 18 day incubated straw (61.53% and 62.86%) followed by 14-day incubated straw (54.27% and 56.49%) as compared to untreated rice straw (C) having 47.12% and 51.68% respectively. Rumen metabolites (total volatile fatty acid, NH₃-N) showed similar trends i.e., substantially highest in 18 day incubated straw (8.11% and 15.83%) followed by 14-day incubated straw (7.17% and 14.23%) and lowest in untreated rice straw (C) having 5.87 mmol/dL TVFA and 11.04 mg/dL NH₃-N, respectively. Thus, straw pretreated with 4% urea, 3% lime and 2% molasses at 18 day incubation had improved the nutritive value of straw and enhanced its in vitro digestibility.

Graphical Abstract

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