Date of Graduation

5-2025

Document Type

Thesis

Degree Name

Bachelor of Science

Degree Level

Undergraduate

Department

Biological Sciences

Advisor/Mentor

Alrubaye, Adnan

Committee Member

Hershberger, Margaret

Second Committee Member

Dong, Bin

Third Committee Member

Holland, Edward

Abstract

Bacterial Chondronecrosis with Osteomyelitis (BCO) is a leading cause of lameness in broiler chickens, impacting animal welfare and commercial poultry production. Supplementation using organic trace minerals, vitamin D, probiotics, and prebiotics has been studied to mitigate BCO lameness incidences in broiler chickens. Our previous study demonstrated that feeding Panbonis®-G-1,25(OH)2D3 from Solanum glaucophyllum, containing 1 µg/kg G-1,25(OH)2D3, to broilers for the first 28 days of their production cycle reduced BCO lameness by approximately 50%. In this study, we investigated the impact of 1,25-dihydroxy vitamin D3 supplementation on the expression of tight junction (TJ) proteins to further understand its mode of action in safeguarding birds from BCO disease.

We measured the mRNA expression of claudins (CLDN1 and CLDN5), occludin (OCLDN), and zonula occludens-1 (ZO-1) in the epithelial barrier of the respiratory and gastrointestinal tracts at 14, 21, and 28 days post-hatch. RNA extraction was performed using the QIAGEN RNeasy Plus Mini Kit, and gene expression was analyzed with RT-qPCR for key TJ genes, with GAPDH serving as a housekeeping gene. Expression levels were quantified using the ΔΔCt method to assess differences between experimental and control groups.

The results revealed a time-dependent pattern of TJ gene expression, with no and limited expression at days 14 and 21, respectively, and significant upregulation at day 28. T3 (1 µg/kg for 21 days) primarily influenced the gastrointestinal tract, while T4 (1 µg/kg for 28 days) had the strongest impact on the respiratory tract. Notably, CLDN1, OCLDN, and ZO-1 showed significant upregulation at day 28 in both the ileum and jejunum, whereas the trachea exhibited substantial changes only in response to T4 supplementation. These findings suggest that TJ protein activity is regulated developmentally and tissue-specifically, highlighting the potential role of gut and respiratory barrier integrity in BCO susceptibility.

Understanding these molecular mechanisms contributes to developing targeted nutritional strategies to reduce lameness in broiler chickens and informs potential genetic markers for selective breeding programs.

Keywords

BCO lameness; Tight Junction; Vitamin D3; Broiler Chickens; RNA Extraction; Gene Expression

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