Newcastle disease is endemic in Nigeria and there are reports of frequent outbreaks both in village and commercial poultry population. Of particular importance and interest is the report in layers particularly at the commencement of production up to peak hen day production. This paper reports preliminary investigations on onset of lay and the development of clinical Newcastle disease. It combined complaints as recorded in two Veterinary clinics for a period of three years and field studies in a layer farm where frequent outbreaks of Newcastle disease were known to have occurred. Data collected showed that 38.1% of Newcastle disease cases recorded within the 3-year period in layers were in young layers between the period of first egg lay to the fourth month of production. The remaining 61.9% was observed in older layers above four months of production life. Parameters taken during the field study showed that unprotected young layers were more susceptible to Newcastle disease infection than older ones. We therefore report that onset of lay can be a stress factor that can alter the immune system of young layers and reduce their resistance to Newcastle disease. We also recommend that pullets should be vaccinated against Newcastle disease at point of lay with strategic management targeted at helping the birds achieve maturity to withstand the stress associated with commencement of lay.
Key words: Newcastle disease, immune system, layers, onset of lay, egg production, stres
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