An exploratory study on the use of antibiotics in the pig chain as an issue for public health and food authenticity

Meat companies have introduced antibiotic-free lines of pork as part of good animal husbandry practices for a responsible use of antimicrobial agents in livestock. Antibiotic free label claim is currently available on the market (Bradford et al, 2022) driven by the urgent need to reduce antimicrobial consumption - and thus antimicrobial resistance - and the growing customer demand. However, these claims lead to new challenges concerning authentication and traceability in the pigs’ chain. A metabolomics approach was employed to highlight putative metabolic differences in pigs due to antimicrobial administration; also, the feasibility of metabolomics as a valuable tool to investigate antimicrobial treatment was evaluated. Liver metabolome of 41 pigs reared in Northern Italy during 2020 was characterized by 1H Nuclear Magnetic Resonance (NMR) spectroscopy. Two groups of pigs, treatment (TX, n=19) and control (CTRL, n=22), were selected according to the Defined Daily Dose Animal for Italy for comparison. A biphasic extraction procedure was adopted to collect the two fractions of liver, polar and non-polar, differently analysed at the 600.17 MHz NMR. A differentiation between TX and CTRL pigs’ groups was observed by performing Orthogonal Partial Least Squared-Discriminant Analysis on polar and non-polar fractions. The most discriminant variables (Variable Importance in Projection > 1) driving the separation between TX and CTRL groups were selected and the statistical significance on relevant features was checked to identify the discriminant molecules and their regulation between the two groups. In liver polar fraction, discriminant molecules up-accumulated (Fold Change Ratio) in TX pigs’ group were glucose, proline, tryptophan, glutathione, lactate, and choline. Higher levels of glucose and lactate in liver may suggest that the observed pigs were in a stressful condition requiring energy. In liver non-polar fraction, decreasing in fatty acids, cholesterol, and unsaturated fatty acids was observed in TX groups, probably due to the consumption of those substrates in case of body energy request. The favourable results achieved so far suggest that the metabolomics approach might be seen as a promising tool for encouraging the intake of fewer drugs with antibacterial activity. Moreover, this technique might improve tracking and authentication systems along the chain of antibiotic-free pigs in confirming label claims and thwarting potential food fraud.