Influence of glyphosate in feed on egg hatchability and health of chicks and breeder hens

1. This study investigated the potential effects of exposure to glyphosate from feed on breeder hens on egg hatchability and chick health. Hens received diets with no added glyphosate (Gly as a control (Con), or with addition of 1.5 (Gly_1.5), 4.5 (Gly_4.5) and 13.5 (Gly_13.5) mg/kg glyphosate in the diet resulting in analysed contents of 0.01, 1,47, 3.59 and 11.6 mg per kg diet, respectively.2. There were no effects of glyphosate in diets fed to breeder hens on hatchability of fertilised eggs (0.95, 0.93, 0.91 and 0.90 for Con, Gly_1.5, Gly_4.5 and Gly_13.5, respectively). Even though no effects of glyphosate were observed on one-day-old progeny chick quality, a <i>post hoc</i> analysis indicated that the navel score was best for chicks from the Con group compared to chicks from the combined Gly groups (<i>p</i> = 0.025). Weight gain of the chicks at 8 d of age was not affected.3. For immune competence and leukocyte subset counts in whole blood from breeder hens and one-day-old chicks, the results showed higher numbers of B-cells (<i>p</i> = 0.005) and monocytes (<i>p</i> = 0.027) as well as phagocytic activity of lymphocytes (<i>p</i> = 0.015). These were associated with higher glyphosate levels in peripheral blood from hens, whereas only phagocytic activity of lymphocytes was seen in chicks (<i>p</i> = 0.004). Total antioxidant capacity in blood plasma of hens and one-day old chicks was not affected.4. In conclusion, only some immune changes were associated in both hens and chicks with up to 11.6 mg glyphosate/kg diet fed to breeder hens.