The effect of leonardite and lignite on the health of weaned piglets.

A three-week trial was conducted to evaluate the effects of leonardite and lignite, natural sources of humic substances, on selected indicators of health status of weaned piglets. A total of 45 weaned piglets were assigned to three dietary treatments: Control - basal diet without any medication; Leonardite or Lignite - diet supplemented with lignite or leonardite at a dose of 20 g/kg, respectively. Leonardite differed from lignite in the content of humic substances and minerals. Diarrhoea incidence and severity, growth performance, haematological and biochemical status, biomarkers of oxidative stress, serum fatty acid (FA) profile and faecal microbiota composition were monitored. Significantly lower faecal score, diarrhoea incidence, serum biomarkers of oxidative stress, higher body weight gain and no mortality were observed in leonardite and lignite group. The supplemented groups had or tended to have higher haematocrit, haemoglobin, erythrocyte counts, iron, cholesterol and lower urea in blood. Increased serum minerals (calcium, phosphorus, magnesium) were detected in the leonardite group. Different effects of leonardite and lignite on serum FA profile were detected. Significantly lower proportion of saturated FA, higher unsaturated, monounsaturated, polyunsaturated (PUFA) n-3 FA and PUFA n6/n3 ratio were detected in leonardite group compared to lignite group. Both treatments decreased microbial diversity and richness of faecal microbiota at the genus level. Specifically, lower relative abundance of Firmicutes, Bacteroides, Anaerovibrio, Oscillospira, SMB53, Ruminococcus, and a tendency to a higher abundance of Prevotella was found compared to control group. Natural humic materials may provide benefit to piglets' heath in the difficult post-weaning period.