SAFEWASTES by-products: in vitro effects on piglet gut flora

Abstract

In healthy piglets, a balanced gut microflora improves digestion and optimal absorption of nutrients and increases the body’s resistance to infectious diseases. During the period of weaning, the major stressful event in the pig’s life, the nutritional and management challenges increase susceptibility to potential pathogens (e.g., Escherichia coli, Salmonella spp., and Clostridium perfringens), due to the immaturity of digestive system and immune system, that may give way to clinically apparent gastrointestinal tract (GIT) disorders or may result in subclinical manifestations. Bacterial toxins, endotoxins or lipopolysaccharides (cell wall components of gram-negative bacteria) can induce immunological stress in piglets and cause inflammation, fever and diarrhoea. As the use of antibiotics to prevent diseases and as growth promoters has been banned, European Union focused on effective alternatives to reduce the incidence of potential pathogenic bacteria in the GI tracts of weaning piglets. The aim of this study was to investigate the effects of specific functional plants and their post-processing derivatives waste products on gut microflora growth or inhibition. The waste products tested are recognised as not harmful for human or animal health and are investigated as efficient alternatives to antimicrobials (SAFEWASTES, EU project n. 513949). Faecal samples from rectal ampulla of piglets (60–70 days of age) were taken by sterile spatula and were introduced in a stomacher bag and diluted 1:10 in 0.9% NaCl/tryptone solution. Decimal dilutions were prepared and aliquots (1mL) were inoculated in Petri plates with specific solid culture media. 1g of each waste products as extract, identified as CS water extract and CS ethanol extract, was solubilised in distilled water (10mL and sterilized by filtration. 10µL, 100µL and 1mL aliquots of solution (100mg/mL) were added to the culture media to obtain three different concentrations of the extract (10µg/mL, 100µg/mL and 1000 µg/mL). The following microbial populations were evaluated: TBC (Plate Count agar); E. coli, Faecal and Total Coliforms (Chromocult agar); Enterococci (Slanetz-Bartley agar); Total Anaerobic Bacterial Count and Clostridia (TSC agar); Lactobacilli (MRS agar).Both tested substances showed a bactericidal effect on Clostridia and didn’t influence commensal microbiota regarded as beneficial to the host. Clostridial counts were reduced by CS extracts at all the concentrations tested, while no effect was observed on Lactobacilli. These results allow us to undertake further investigations to confirm the antimicrobial activity of these potential feed additives also in vivo.