Age‐related effect of high‐frequency photostimulation on Blood Physiological Variables in laying hens

Abstract

Light is a crucial environmental factor that affects bird's development, production performance, well-being, and quality of egg production. A novel lighting system has been developed to improve photostimulation of growth and egg laying performance for layer chickens. However, it has not been independently investigated by scientists to observe its effects on layer chicken well-being responses. This study investigated the whole blood physiological variables of laying hens to high-frequency differential photostimulation. A total of 320-layer pullets were obtained from a commercial hatchery at approximately 10 weeks of age and randomly allocated to 16 groups of 20 birds per group. Birds were weighed (group size = 20) and randomly assigned to each of four cage banks in each 4 rooms (A to D) with 80 birds per room. Experimental treatments included the prototype LED lighting system and conventional 2700K LED bulbs. The prototype LED lighting system were installed in two rooms, and the conventional lighting system were employed in the remaining two rooms. Photoperiod for the prototype system was 24L:0D per the manufacturer's recommendations and photoperiod for the conventional system followed the HyLine Management Guide (12 to 16 hours of light, increasing from 10 to 30 weeks of age). Blood samples (3 ml) were collected from the brachial wing vein into heparinized syringes within 45 s after birds were caught from 8 randomly selected birds per room for a total of 32 birds at each blood sampling day of placement, 15 weeks of age (prior to point of lay), and at the termination of the study at 30 weeks of age for a total of 96 birds, which were then analyzed immediately for whole blood physiological variables. The remaining blood samples were centrifuged to collect plasma that was used for T3, T4, and corticosterone analysis. Results show that only Hb and Hct were affected by treatments. However, time (age) had significant effects on most examined variables. Plasma corticosterone was not affected by treatments and time, indicating absence of physiological stress. The results contribute to our knowledge of prototype LED light on blood metabolites variation in layer hens. In conclusion, using high-frequency photostimulation in layer hens house does not negatively affect layer hen's welfare.