# Effects of Monochromatic Light on the Development of Immune Organs, Antioxidant Capacity and Immune Response of Thymus and Bursal of Fabricius in Yangzhou Geese

## TL;DR

This study shows that green and blue light improve immune function and antioxidant capacity in Yangzhou geese, while red light has the opposite effect.

## Contribution

The study provides new empirical evidence on how monochromatic light affects immune and antioxidant systems in geese.

## Key findings

- Green and blue light increased thymus and bursa indices and PCNA expression in Yangzhou geese.
- Green and blue light elevated anti-inflammatory IL-10 and immunoglobulins while reducing pro-inflammatory cytokines.
- Red light inhibited immune and antioxidant responses compared to green and blue light.

## Abstract

Preliminary investigations suggest that exposure to monochromatic green light enhances growth in Yangzhou geese at 70 days of age. However, the impact of light color on the development of immune organs, antioxidant capacity, and immune response remains unverified by conclusive research. In this study, 240 Yangzhou geese were randomly allocated into four treatment groups (n = 60 per group), with each group further divided into four replicates (15 geese per replicate). During the experimental period, the geese were exposed to a photoperiod consisting of 16 h of light and 8 h of darkness, with the light conditions being white light (WL), green light (GL), blue light (BL), or red light (RL) over a span of 70 days. Serum cytokine and immunoglobulin concentrations, immune organ indices, immune organ morphology, proliferating cell nuclear antigen (PCNA) expression in thymus and bursa of Fabricius cells, antioxidant capacity in the thymus and bursa of Fabricius, and melatonin receptor expression levels were assessed. The results demonstrated that exposure to green and blue light significantly enhanced immune responses and antioxidant capacity in Yangzhou geese, whereas red light exerted an opposing effect.

Light color is a key environmental factor regulating poultry immunity, but research data on geese remains limited. This study aimed to evaluate the effects of monochromatic light on the development of immune organs, antioxidant capacity, and immune response in Yangzhou geese. In this study, 240 male Yangzhou geese (4 replicates × 15 birds) were randomly assigned to white (400–700 nm), green (560 nm), blue (480 nm), or red (660 nm) light treatments for 70 days. In comparison to the white light (WL), both green light (GL) and blue light (BL) significantly enhanced the indices of thymus and bursa of Fabricius and upregulated proliferating cell nuclear antigen (PCNA) expression. These treatments also resulted in elevated serum levels of the anti-inflammatory factor IL-10 and immunoglobulins, while concurrently suppressing pro-inflammatory cytokines. Moreover, exposure to GL and BL significantly upregulated the mRNA expression of melatonin membrane receptors, whereas red light (RL) activated the mRNA expression of nuclear receptors. Furthermore, antioxidant enzyme activities were significantly elevated under GL conditions, along with a decreased malondialdehyde (MDA) content, in comparison to those under WL. These results indicate that GL and BL significantly enhance immune response and antioxidant defense in Yangzhou geese, whereas RL exerts inhibitory effects.