Identification of Bioactive Phytochemicals from Six Plants: Mechanistic Insights into the Inhibition of Rumen Protozoa, Ammoniagenesis, and α-Glucosidase.

Aurele Gnetegha Ayemele,Zhongtang Yu,Lu Ma,Jianchu Xu,Dengpan Bu,Peilong Yang,Xiumei Li

doi:10.3390/biology10101055

Abstract

Simple SummaryRumen protozoa have some contribution to feed digestibility in the rumen, but Entodinium, the most predominant genus, is the main culprit of inefficient nitrogen utilization in ruminants. Using chemical drugs, many studies have attempted to inhibit the rumen protozoa, but few of the approaches are either effective or practical. In this study, we investigated the nutritional and functional properties of Adansonia digitata (baobab), Flemingia macrophylla (waras tree), Kalimeris indica (Indian aster), Brassica rapa subsp. chinensis (bok choy), Portulaca oleracea (common purslane), and Calotropis gigantea (giant milkweed) for their potential as feed additives in animal husbandry. The plants were also analyzed for their major phytochemicals using reversed phase-high performance liquid chromatography (HPLC) and then evaluated for their ability to inhibit rumen protozoa, ammoniagenesis, and microbial α-glucosidase activity in vitro. C. gigantea inhibited the rumen protozoa and reduced the wasteful ammoniagenesis, thereby indicating improved nitrogen utilization. A. digitata also reduced the microbial α-glucosidase activity that can potentially contribute to rumen acidosis. The tested plants, especially C. gigantea and A. digitata, could be used as potential alternatives to chemicals or antibiotics to ensure sustainable and green animal husbandry.Rumen protozoa prey on feed-degrading bacteria synthesizing microbial protein, lowering nitrogen utilization efficiency in ruminants. In this in vitro study, we evaluated six plants (Adansonia digitata, Flemingia macrophylla, Kalimeris indica, Brassica rapa subsp. chinensis, Portulaca oleracea, and Calotropis gigantea) for their potential to inhibit rumen protozoa and identified the phytochemicals potentially responsible for protozoa inhibition. Rumen protozoa were anaerobically cultured in vitro in the presence of each plant at four doses. All of the tested plants reduced total rumen protozoa (p ≤ 0.05), but C. gigantea and B. rapa were the most inhibitory, inhibiting rumen protozoa by 45.6 and 65.7%, respectively, at the dose of 1.1 mg/mL. Scanning electron microscopy revealed a disruption of the extracellular structure of protozoa cells. Only C. gigantea also decreased the wasteful ammoniagenesis (p ≤ 0.05). Moreover, the A. digitata extract inhibited α-glucosidase activity by about 70% at 100 µg/mL. Reversed-phase high-performance liquid chromatography analysis detected quercetin, anthraquinone, 3-hydroxybenzoic acid, astragaloside, and myricetin in the tested plant leaves. These plants may hold potential as feed additives to reduce rumen protozoa and α- glucosidase activity. Future research is needed to identify the specific anti-protozoal compound(s), the effects on the rumen microbiome, and its fermentation characteristics.

Highlights

Ruminants can convert fibrous plant materials into meat and milk for human consumption
Ether extract, fiber, and ash were the main nutrients detected on a dry matter (DM) basis (Table 1)
The ether extract content was no more than 1.9% of any of the tested plants, except for C. gigantea, which recorded the highest value (3.9%)

Summary

Introduction

Ruminants can convert fibrous plant materials into meat and milk for human consumption. Rumen protozoa engulf the cells of rumen microbes (primarily bacteria), which are the main source of metabolizable protein for the host animals, and degrade the microbial protein into oligopeptides and free amino acids, both of which are converted to ammonia, lowering NUE [2]. Some antimicrobials have been used to improve feed utilization efficiency including NUE, but some side effects on both animal products and human consumers have been reported [3]. This led to the ban of antimicrobials as feed additives and calls for renewed interest in using plants as a source of natural alternatives, especially in organic animal husbandry. A recent study [4]

Objectives

Results

Discussion

Conclusion