Date of Graduation

5-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Cell & Molecular Biology (PhD)

Degree Level

Graduate

Department

Cell & Molecular Biology

Advisor/Mentor

Alrubaye, Adnan A.

Committee Member

Kwon, Young Min

Second Committee Member

Sun, Xiaolun

Third Committee Member

Fan, Chenguang

Keywords

BCO lameness; Broilers; Microalgae; Organic Trace Mineral; Skeletal disorder; Vitamin D3

Abstract

As the global population grows, the supply and demand for meat have dramatically increased. The poultry industry has managed to satisfy the high demand for chicken meat through fast-growing broilers. The poultry breeder industry has successfully provided modern broilers with high liveability, feed efficiency, and processing yields through genetic selection of the traits of interest such as growth rate, feed conversion rate, and breast quality. Nevertheless, the intensive selection of modern broiler chickens for fast growth and feed efficiency leads to unintended side effects, such as excessive fat, low reproductive performance, leg abnormalities, low immunity, cardiovascular diseases, and metabolic disorders. Lameness resulting from Bacterial Chondronecrosis with Osteomyelitis (BCO) in the long bones of the leg is a result of non-synchronized high body weight accretion with skeletal bone maturation of rapid-growth broilers. BCO lameness is initiated by micro-trauma and inflammation in the proximal growth plates of the leg bones and followed by infection of hematogenous bacteria in the growth plate of the long bones. BCO lameness leads to huge economic losses, food safety concerns, and animal well-being issues in the poultry industry. Therefore, effective intervention measures in controlling BCO lameness in poultry to minimize financial loss and health impact are highly required. In this study, we developed measures to alleviate BCO diseases in broilers through a model of inducing BCO and dietary supplementation. A reliable model to generate experimental BCO is pivotal in investigating etiology, pathogenesis, and intervention strategies mitigating BCO. We developed an aerosol transmission model as an alternative approach to induce experimental BCO lameness mimicking epidemic BCO in commercial farms. The model employs a group of birds reared on wire-flooring pens as a BCO infection source and the disease is further transmitted through airborne transmission to the treatment groups reared on litter flooring in the same housing environment. The effectiveness of the aerosol transmission model in inducing BCO lameness was measured from four independent experiments presenting that the cumulative lameness generated from the wire floors was successfully transmitted to the birds on litter floors without significant statistical differences. Furthermore, we also investigated the efficacy of several feed additives, particularly Spirulina microalgae, organic trace minerals, and 1,25(OH)2D3-glycosides, in reducing BCO lameness. Our findings suggested that the inclusion of 5% Spirulina platensis did not reduce BCO lameness, while 0.15% of Availa® ZMC containing the trace minerals-zinc, manganese, and copper, significantly alleviated lameness. When combined, there was no significant interaction between Availa® ZMC and microalgae in mitigating broiler lameness. Our next finding demonstrated that feeding 1.0 µg/kg of Solanum glaucophyllum-derived 1,25(OH)2D3-glycosides for the first 28 days is the optimum concentration and timing for 1,25(OH)2D3-glycosides administration protecting broilers from BCO for the entire production cycle. This early feeding strategy would minimize feed additive costs without compromising bone health while promoting resistance against BCO lameness. In conclusion, we anticipate that the study reported in this dissertation can contribute to mitigate the economic loss, animal welfare issues, and food safety risks of BCO lameness in broiler poultry.

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