Toxicological Assessment of Sub-Acute Exposure to Glyphosate in Laying Hens in Ogun State

Glyphosate-based herbicides are the most widely used pesticides globally and their use in Nigerian crop production has increased substantially over the last decade, raising concerns about residue exposure in poultry consuming contaminated feed ingredients. Laying hens used in commercial egg production in Ogun State, South West Nigeria, may be exposed to glyphosate through soybeans and maize meal derived from treated crops. This study assessed the toxicological effects of sub-acute oral glyphosate exposure on laying performance, haematology, serum biochemistry, and intestinal histopathology in Isa Brown laying hens. Eighty hens were allocated to four groups receiving diets containing 0, 50, 150, and 300 mg/kg glyphosate residue for 28 days. Egg production rate, egg quality parameters, and body weight were recorded weekly. Blood samples were collected at days 14 and 28 for haematological and biochemical analysis. Intestinal sections were collected at termination for histopathological examination. Hens receiving 300 mg/kg showed a significant decline in egg production rate from 82.4 to 64.7 percent by week four and significantly reduced eggshell thickness. Serum alanine aminotransferase and aspartate aminotransferase were significantly elevated at both 150 and 300 mg/kg by day 28, indicating hepatotoxicity. PCV and haemoglobin were significantly reduced at the highest dose. Intestinal histopathology revealed villus atrophy and crypt hyperplasia at 300 mg/kg, consistent with gut dysbiosis-related pathology. These findings demonstrate that glyphosate at residue levels potentially encountered in Nigerian poultry diets can significantly impair laying performance and health parameters. Keywords: glyphosate, laying hens, toxicology, Ogun State, sub-acute.