Effects of Different Pen Lighting Sources on Growth, Feed Efficiency and Gene Expression in Blood and Liver of Broiler Chickens.

Several reports suggest use of light-emitting diode (LED) lights of various colors may improve efficiency of broiler production. The objective was to compare effects of different light sources on growth and gene expression of broilers. In a subset of a larger experiment, 48 Cobb 500 strain chicks were assigned to one of six lighting treatments with 8 birds per treatment: 1) incandescent, INC); 2) fluorescent (FL); 3) white LED (WL); 4) green LED (GL); 5) blue LED (BL); or 6) green LED on days 1-9 followed by blue LED on days 10-17 (GB). Treatments were administered by using bulbs that met the above specifications. Feed and water were available ad libitum. At termination on day 17, body weight and feed intake were determined and blood and liver samples were obtained for RNA analysis. Blood RNA was used for RNAseq analysis on a subset of samples (n=4/treatment for WL, GL and BL) to identify target genes for further analysis. Treatment effects were analyzed by orthogonal contrasts and genes were considered differentially expressed (DE) when P ≤ 0.001 and FDR ≤ 0.10. Comparing white and colored LED light (WL versus the average of GL and BL) revealed 63 DE genes. Comparing GL to BL identified 107 DE genes. Integrative analysis using DAVID software indicated: Functions including signal, secreted, blood microparticles, extracellular exosomes and plasma membrane; KEGG pathways, including PPAR signaling; and Tissue specificity, indicating liver. Based on those analyses, we selected 12 DE genes for analysis in liver RNA by qPCR. Target genes included AvBD9, APOA4, CAT, CHAC1, FOXN2, HMGCS1, IL15, SCD, SPINK5, TTR, UBAP2, XPA. Target gene expression was normalized to that of a reference gene, RPL4, and data were log2 transformed before analysis using Proc GLM of SAS. Genes were considered DE at P < 0.05. There was no effect (P > 0.05) of any lighting treatment on expression of the selected genes of interest in liver. Similar to liver gene expression, light treatments had no effect on broiler growth, feed intake or feed efficiency to day 17 (P > 0.05). In summary, different light treatments altered gene expression in blood cells but not liver and had no effect on broiler performance. Conflicting gene expression in blood and liver suggests cell type specificity in response to lighting. Similarity of broiler performance under different lighting suggests LED lights of various colors can be used to reducing operating costs without penalizing performance.