The effect of monochromatic light on the blood picture and functional state of the hematopoietic system in laying hens

This study aimed to investigate the influence of monochromatic lighting on the haematological indices of Hy-Line W-36 laying hens. In the course of the experiment, four groups of birds were exposed to monochromatic lighting of different wavelengths: blue, green, yellow and red. The haematological study included analysis of leukocyte, erythrocyte and thrombocyte count, haemoglobin concentration, haematocrit and erythrocyte sedimentation rate (ESR). It was found that the colour composition of light affects the hematopoietic system of hens. The activity of white blood cells gradually decreases in the series of transition from short- to long-wavelength light, which indicates the weakening of immune stimulation under the influence of warm light. The content of haemoglobin and haematocrit increases under the yellow and red light, which indicates the activation of erythropoiesis and an increase in the volume of formed blood elements. The number of erythrocytes increases in the yellow and red spectrum, while thrombocytes are most sensitive to long‑wave radiation, which indicates the activation of the megakaryocytic lineage. The ESR decreases with an increase in the wavelength, which indicates the stabilisation of blood viscosity and a decrease in the aggregation of erythrocytes. One-way analysis of variance showed a significant effect of the colour composition of light on all studied indices. Thus, the analysis of experimental data indicates a clear dependence of the haematological status of laying hens on the spectral composition of lighting. In particular, replacing the blue light with red light resulted in a decrease in the number of leukocytes by 45.6% (p < 0.001), while the content of haemoglobin increased by 51.8% under the red spectrum compared to the blue one (p < 0.001). Additionally, the red light exposure led to an increase in the number of erythrocytes by 52.2% (p < 0.001) and a decrease in their sedimentation rate by 22.6% (p < 0.001). The results of the study are the scientific basis for the development of recommendations on the use of monochromatic and mixed lighting modes for optimising the productivity and increasing the stress resistance of laying hens