Abstract
This study is aimed at evaluating antibody responses, viral loads, viral clearance and growth rate of Tanzanian free-range local chicken (FRLC) challenged with LaSota strain of Newcastle disease virus (NDV) as indicator traits for selection of chickens for breeding with enhanced resistance to the disease and economic value. Three popular free-range local chicken ecotypes: Kuchi, Ching’wekwe and Morogoro-medium from three ecological zones of Tanzania were used for the experiments. Progenies from the breeder chickens were challenged with 107 titer of 50% egg infectious dose (EID50) of the virus at 28 days of age. The viral loads and viral clearance rates evaluated by qRT-PCR from tear samples collected at 2- and 6-days post infection (dpi) showed that Kuchi could clear NDV better than Morogoro-medium and Ching’wekwe. Anti-NDV antibody levels determined from blood samples collected at 10 dpi using ELISA showed that Kuchi ecotype expressed higher mean anti-NDV antibodies compared to Morogoro-medium and Ching’wekwe. Growth rates determined from body weights collected for 38 days from day of hatch (D0) to 10 dpi showed higher growth rate for Kuchi than Morogoro-medium and Ching’wekwe chickens. Kuchi chickens were potentially more resistant to ND compared to Morogoro-medium and Ching’wekwe. Key words: Free-range local chickens, Newcastle disease, immune response, innate resistance.
Highlights
Newcastle disease (ND) is one of the major devastating diseases in poultry worldwide (Ferreira et al, 2019; Miller and Koch, 2013)
This study aimed to evaluate the natural resistance of Tanzanian free-range local chicken (FRLC) to ND using antibody response, viral load and viral clearance rate as indicator traits for resistance to the disease
This study was designed to characterize three Tanzanian FRLC ecotypes in terms of their antibody response, viral load, viral clearance rates and effects on growth rate upon challenge with the LaSota strain of Newcastle disease virus (NDV), a nonpathogenic strain of the virus commonly used as a vaccine to protect poultry from ND
Summary
Newcastle disease (ND) is one of the major devastating diseases in poultry worldwide (Ferreira et al, 2019; Miller and Koch, 2013). The disease is endemic in Tanzania and frequently causes outbreaks in free-range local chicken (FRLC) flocks. Control of ND in Tanzanian FRLC flocks will improve their survivability and productivity, and contribute to availability of animal protein in human diet as well as improved family income. The control of ND in the Tanzanian FRLC flocks has been and is still a big challenge due to the free-range nature of the husbandry system in practice which exposes them to the risk of ND. Vaccination in combination with biosecurity measures has been important in control of many diseases including ND and infectious bursal disease (IBD) in commercial poultry (Alders et al, 2012) but not practicable in FRLC flocks
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