Abstract
The objective of this study was to evaluate the effects of Valerian (Valeriana officinalis L.) extract added to drinking water on productive performance, egg quality, and stress indicators in laying quails (Coturnix japonica) under different stocking densities, with emphasis on their interaction with valerian supplementation. A total of 180 females, 9 weeks of age, were randomly allocated to cages and assigned to two Valerian extract levels (0 and 4 mg/mL of water) and three stocking densities (1, 2, or 3 birds per cage) for seven weeks. Productive performance (body weight, feed intake, laying rate, and egg mass), external and internal egg quality traits, tonic immobility duration, heterophil-to-lymphocyte ratio, corticosterone concentration, and haematological parameters were evaluated. Valerian extract supplementation did not affect productive performance or overall egg quality (p > 0.05). Feed intake was influenced by stocking density (p < 0.05), being lowest in singly housed birds, while shell thickness was reduced in quails receiving Valerian extract. Valerian supplementation significantly reduced corticosterone concentration (from 0.62 to 0.38 µg/dL; p < 0.01) and numerically lowered the heterophil-to-lymphocyte ratio (from 1.52 to 1.15; p = 0.078), whereas higher stocking densities tended to increase stress indicators. Significant Valerian × density interactions were observed for shell thickness, albumen height, yolk height, yolk color, heterophil-to-lymphocyte ratio, haematocrit and eosinophil counts, and stocking density affected monocyte percentages (p < 0.05). In conclusion, Valerian extract administered via drinking water reduced physiological stress indicators without affecting productive performance or egg quality under the evaluated stocking densities.