Enhancing feed fermentation in rice straw basal diets using leaf protein concentrate as a novel ruminant supplement derived from Indigofera zollingeriana
Authors: Puastuti Wisri , Yulistiani Dwi , Haryati Tuti , Rakhmani Susana Insusila Watining , Widiawati Yeni , Kusumaningrum Diana Andrianita , Wina Elizabeth , Jayanegara Anuraga , Anda Markus 
Published: September 2024

Background and Aim: Rice straw, a widely available agricultural byproduct globally, has significant potential as a basal diet for livestock. The major challenge lies in obtaining high-protein foliage that can be easily extracted using natural water rather than chemical solvents. This study aimed to assess the ability of distilled water to extract protein concentrate from Indigofera leaves (Indigofera zollingeriana Miq.) and to evaluate its effectiveness in enhancing rumen feed fermentation and digestibility in low-quality rice straw basal diets.

Materials and Methods: The study was conducted in two experimental series. Experiment 1 was designed to explore the ability of distilled water to extract protein concentrate from fresh and dry Indigofera leaves by comparing it with the 0.1 N NaOH standard solvent. Experiment 2 focused on the in vitro digestibility of protein concentrates extracted from fresh Indigofera leaves based on optimal findings from experiment 1. Five treatments consisting of 0.5% and 1.0% protein concentrate and two extractants (distilled water and 0.1 N NaOH) were used to extract protein from Indigofera leaves. These extracts were then added to rice straw-based diets. Rice straw without supplements was used as a control. The treatments were arranged using a randomized complete design with five replicates.

Results: The results of experiment 1 showed that distilled water was superior to 0.1 N NaOH for extracting protein concentrate from fresh Indigofera leaves, as revealed by higher dry matter, protein yield, total amino acids (AA), and total essential AA (EAA) production. For in vitro experiment 2, supplementation with distilled water-extracted protein concentrates successfully increased rumen fermentation and digestibility in rice straw basal diets, as indicated by higher gas production, total volatile fatty acid, and microbial protein levels compared with 0.1 N NaOH.

Conclusion: Findings from this study confirm that Indigofera leaf protein concentrate offers a new alternative for enhancing rumen feed fermentation and the digestibility of low-quality rice straw diets. This study implies that it is an easy, cost-effective, and environmentally friendly approach, particularly beneficial for smallholders, to extract protein concentrate from fresh Indigofera leaves using distilled water and use it to enhance the quality of rice straw for ruminant feed. The limitation of this study is that the Indigofera supplement was established using in vitro digestibility under controlled laboratory conditions, which does not reflect real rumen conditions. Therefore, further studies using in vivo digestibility in ruminant animals are required to confirm the ability of the protein extracted from indigofera to enhance rumen feed fermentation in low-protein basal diets.

Keywords: distilled water solvent, Indigofera, leaf protein concentrate, rice straw, rumen fermentation.