Enhancing the nutritional quality and digestibility of citronella waste (Cymbopogon nardus) for ruminant feed through ammoniation and fermentation techniques

Abstract

Background and Aim: Citronella grass (Cymbopogon nardus) waste, produced by distilling citronella to produce essential oil, has a high potential for use as animal feed. However, the presence of high lignin content could limit its digestibility, prompting the need for treatment to improve its quality. This study aimed to improve the nutritional value and in vitro digestibility of ammoniated and fermented citronella waste (CW). Materials and Methods: The treatments of CW included CW without treatment as a control (T0), ammoniation of CW with urea (T1), fermentation of CW with Trichoderma harzianum (T2), and a combination of ammoniation and fermentation (amofer) of CW (T3). This study employed a randomized block design with five replicates for each of the four treatments. If there was a significant effect (p < 0.05), a post hoc Duncan’s multiple range test was performed to analyze the variance of the data. Results: The process of ammoniation and fermentation led to a notable increase in crude protein (2%–6%) while decreasing crude fiber (2%–6%), neutral detergent fiber (NDF) (5%–14%), acid detergent fiber (ADF) (5%–9%), lignin (4%–9%), and cellulose (2%–10%). The treatments enhanced the digestibility of dry matter, organic matter (OM), NH3, and total volatile fatty acid by 4%–12%, 6%–19%, 0.9–10 mM, and 35–142 mM, respectively. The decrease in NDF, ADF, acid detergent lignin (ADL), and cellulose fractions was accompanied by an improvement in dry matter and OM digestibility in CW. Ammoniated-fermented (amofer) CW, followed by fermentation with T. harzianum and ammoniated urea treatment, significantly enhanced the nutritional content and in vitro digestibility. The decrease in NDF, ADF, ADL, and cellulose fractions led to an improvement in dry matter and OM digestibility in CW. Conclusion: The application of amofer treatment with T. harzianum maximizes CW’s nutritional value and digestibility, making it the most efficient preservation method. Research is needed to explore the potential use of Aspergillus spp. and Pleurotus spp. for fermenting CW as ruminant fodder. Keywords: ammoniation, Cymbopogon nardus, digestibility, fermentation, Trichoderma harzianum.