An in vitro investigation into the potential benefits of Psychotria zombamontana as a poultry feed additive

Abstract

Poultry feed is one of the main constraints, after disease, in poultry production for smallholder farmers in Africa. It also acts as the first step of the food safety chain in the “farm to fork” model. With the poultry industry being the largest individual agricultural industry in South Africa, the nature of the microorganisms present in the feed is of great importance. Problematic microorganisms may lead to an increased feed conversion ratio of livestock, illness or disease in livestock, or even disease in humans. The primary aim of this study was to evaluate the activity of Psychotria zombamontana (Rubiaceae) against problematic fungi and bacteria that may be associated with poultry feed. This species was selected following promising preliminary antifungal results. Additionally, further biological activities that may be beneficial to the chickens when added to the feed were evaluated, including antioxidant and anti-inflammatory activity. Acetone leaf extracts of P. zombamontana showed promising activity against all microorganisms tested as well as very high antioxidant activity and anti-inflammatory activity. An effort was made to isolate the active compounds through bioassay-guided fractionation. Two active sub-fractions were obtained from the acetone leaf extract of P. zombamontana. Both sub-fractions were found to have antimicrobial activity, and have an effect on cytokine production. One of the sub-fractions also displayed promising activity against 15-lipoxygenase, an enzyme implicated in inflammation. Compounds within the two sub-fractions were identified using gas chromatography-mass spectroscopy (GC-MS). Results of this analysis suggested that the sub-fractions comprised a number of compounds, but only the major compounds were reported as many were present in negligible amounts. Some of the compounds identified were reportedly inactive, while the rest have previously been investigated and shown to have activities which correlated with the activity observed for the P. zombamontana extract during this study. The extract and sub-fractions were also investigated for cytotoxicity for preliminary evidence of safe ingestion of plant material or compound by poultry. Results show that the extract and sub-fractions were relatively non-cytotoxic and therefore may be safe for ingestion, but in vivo studies are necessary to confirm this. These findings, coupled with the promising antimicrobial, antioxidant and anti-inflammatory activity, suggest that P. zombamontana could be a highly beneficial addition to poultry feed. It may be possible for the plant material to be used by smallholder farmers as a form of alternative control of fungal contaminants. Furthermore, a functional product may be formulated using this plant for use by commercial farmers. This encourages further studies in vivo to more closely investigate the effects of the crude plant material as well as pure compounds on poultry when added to feed. Additionally, further studies should aim to observe the curative effect of the extract or compounds on artificially infected poultry, as well as any possible preservative effect the material may have on the feed.