# Assessment of Various Tissues in Broilers Reared Under Different Lighting Programs with Respect to Rearing Disorders

## TL;DR

This study found that gradual light transitions in broiler rearing had minor effects on heart and eye weights but did not significantly impact musculoskeletal disorders or bone health.

## Contribution

The study provides new insights into the effects of light transition duration on organ weights and rearing disorders in broilers.

## Key findings

- Gradual light transitions did not affect major musculoskeletal disorders in broilers.
- Broilers in the 30-min gradual transition group had higher relative heart weights than those in the abrupt-transition group.
- A 1-h gradual transition led to significantly greater eye weights compared to abrupt and 30-min transitions.

## Abstract

Lighting programs are an important management factor in intensive broiler production. This study evaluated whether abrupt or gradual transitions between light and dark periods influence organ development and the occurrence of rearing-related disorders in broilers. The findings showed that different light transition regimes did not affect the occurrence of major musculoskeletal disorders. Gradual light transitions resulted in minor differences in some organ weights but did not lead to clear health advantages compared to abrupt transitions. These results indicate that extending light–dark transition periods beyond short gradual changes may not provide additional practical benefits in broiler production.

This study aimed to assess the impact of gradual versus abrupt light–dark transitions on the pectoral muscle, heart, tibia, and eye tissues of broilers, focusing on rearing disorders. A total of 270 male broiler chicks (ROSS-308) were divided into three groups according to the type of light transition: abrupt, 30-min gradual, and 1-h gradual changes in light intensity. The broilers were reared for six weeks, after which samples were collected for gross examination, morphometric and histomorphometric measurements, and histopathological analysis of the pectoral muscle, heart, tibia, and eye. White striping incidence in the pectoral muscle was not significantly affected by light–dark transition type. Results indicated that broilers in the 30-min gradual transition group had a higher relative heart weight than those in the abrupt-transition group (p < 0.05), although the RV/TV ratio did not differ. Tibial measurements, including weight, length, and cortical index, showed no differences across groups. Broilers exposed to a 1-h gradual transition between light and dark periods showed significantly greater eye weights compared to both the birds in the abrupt transition group and the birds in the 30-min transition group (p < 0.01). Overall, gradual light transitions did not substantially affect pectoral muscle or bone health but had minor effects on heart and eye weights in broilers reared under intensive production systems.