Effect of Newcastle Disease Virus (Kudu 113) Infection on Calcium Metabolism in Response to Endocrinological Changes in Commercial Layers

Abstract

The effect of experimental Newcastle disease virus (NDV) infection on some aspects relating to endocrinology of calcium metabolism, which affects eggshell quality and production, was studied. Twenty 22-week-old ISA brown layers vaccinated against Newcastle disease (ND) were allocated to infected and uninfected groups of 10 chickens each. The chickens in the infected group were inoculated intranasally with 0.1 ml of NDV (Kudu 113 strain). Blood samples were collected every other day for the first week, weekly for 5 weeks and analysed for haematology and serum chemistry. Clinical signs such as anorexia, ruffled feathers, greenish diarrhoea, misshapen, small-sized and white-shelled eggs were observed in the infected chickens from day 3 post infection (pi). The eggshell abnormalities were observed in the 2^nd and 3^rd week pi, which subsequently normalized. The mean packed cell volume (PCV) in the infected chickens on day 6 pi was significantly lower (P<0.05) than that of the uninfected. There was a significant difference in plasma calcium levels between both groups. There were significant decreases in the concentrations of calcium and phosphorus from onset to day 18 and then an increase in phosphorus on day 25. Plasma oestrogen activity showed a significant increase (P<0.05) from onset to day 18 and then decreased on day 25 pi. The activity of parathormone also increased progressively until day 32 pi. From this study, ND induced decline in plasma calcium and phosphorus levels which triggered an increase in oestrogen and parathormone activity with a consequent rise in plasma calcium and phosphorus levels.

Key words: Newcastle Disease, Calcium, Oestrogen, Parathormone