Effect of chronic dietary glyphosate based herbicide on chicken caecal microbiome
Glyphosate-based herbicides (GBH) are massively used in agriculture. However, few studies investigated the GBH effects on avian species whereas they are largely exposed via their food. Here, we investigated the potential reversibility of the effects of a chronic dietary exposure to a GBH in hen broiler. During 42 days, we exposed 32 weeks-old hens to GBH via their food (47 mg/kg/day glyphosate equivalent, GBH, n=75) corresponding to half glyphosate's No-Observed-Adverse-Effect-Level in birds. We compared their performances to the 75 control animals (CT). Both groups (GBH and CT) were then fed for 28 additional days without GBH exposure (Ex-GBH and Ex-CT). GBH temporarily increased the plasma glyphosate and AMPA (Amino-Methyl-Phosphonic Acid) concentrations. Glyphosate and AMPA mostly accumulated in the liver and to a lesser extend in the leg muscle and abdominal adipose tissue. GBH also temporarily increased the gizzard weight and the plasma oxidative stress monitored by TBARS (Thiobarbituric Acid Reactive Susbtances). GBH temporarily decreased the ceacal concentrations of propionate, isobutyrate and propionate but acetate and valerate were durably reduced. The ceacal microbiome was also durably affected since GBH inhibited Barnesiella and favored Alloprevotella. Body weight, fattening, food intake and feeding behavior but also plasma lipid and uric acid were unaffected by GBH. Taken together, our results show possible disturbances of the caecal microbiota associated to plasma oxidative stress and accumulation of glyphosate in metabolic tissues in response to dietary GBH exposure in broiler hens. Luckily, GHB at this concentration does not hamper growth and most of the effects on the phenotypes are reversible.