Oral Tulbaghia violacea extract-based nano-ZnO administration in piglets fed diets supplemented with naturally mycotoxin-contaminated marula seed cake

Abstract

The high costs of conventional protein sources such as soya bean meal (SBM) have prompted the search for a cheaper alternative and readily available protein sources like marula seed cake (MSC) for pig production, particularly by smallholder farmers in Southern Africa. Marula seed cake (MSC) has a high crude protein and amino acid content similarly to SBM. Due to its high content of protein and residual oil, both of which provide ideal conditions for the growth and proliferation of toxigenic fungi, MSC is however naturally contaminated with mycotoxins. Mycotoxins are known to induce deleterious effects and cause economic losses in pigs by causing reduced growth, immunosuppression and other effects. Hence the need to find strategies to counter their deleterious effects in pigs fed MSC-supplemented diets. This study was aimed at investigating ameliorative effects of T. violacea bulb extract bio-fabricated zinc oxide (ZnO) nanoparticles (Nano-ZnO) in piglets fed diets supplemented with naturally mycotoxin-contaminated MSC. Nano-ZnO was phyto-synthesized using the aqueous leaf extract of T. violacea as reducing and stabilizing agent. The synthesized ZnO NPs were characterized by techniques including X-ray diffraction (XRD), UV–visible spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) spectrometer. The morphological studies confirmed that the as-prepared ZnO NPs were spherical, with an average particle diameter of 45.26 nm. The PXRD pattern indicated single-phase hexagonal ZnO NPs with high crystallinity, while the absorption spectra showed evidence of quantum size effect. The Nano-ZnO were applied in a piglet feeding trial by orally administering (gavaging) them to piglets fed diets supplemented with naturally-mycotoxin contaminated MSC. A total of 60, 4-week old weaned Large White piglets were randomly allocated to two (2) iso-energetic and iso-nitrogenous diets formulated by replacing SBM (Control; 0% MSC) (Group A) with MSC (Treatment; 20% MSC) (Group B). Once-daily, Group A piglets (0% MSC) were orally drenched with 10 mL of the vehicle (25% ethanol in water; 25 parts ethanol: 75 parts water, v/v) whilst Group B piglets (20% MSC) were similarly orally drenched with an equivalent volume of the: vehicle (25% ethanol) (Group B1), 50 mg/L of bulk ZnO in 25% ethanol (Group B2), 50 mg/L of chemically-synthesised Nano-ZnO in 25% ethanol (Group B3), and 50 mg/L of green (T. violacea bulb extract-fabricated) Nano-ZnO in 25% ethanol (Group B4). Average feed intake (FI) and body weight gain (BWG) were measured weekly, and then feed conversion efficiency (FCE) was calculated by dividing the BWG by the FI. On day 33, blood was collected for serum analysis, and all animals were slaughtered after which carcass and meat quality measurements were taken. The ...