Abstract
ABSTRACTThis study evaluated the changes that occurred in the serum levels of calcium and phosphorus in laying hens infected with velogenic Newcastle disease (ND) virus (vNDV), and their relationship to the decrease in egg production usually associated with ND. Two hundred and forty laying hens (32 weeks old) were randomly assigned into four groups of 60 each viz: VAI – vaccinated with ND vaccines and intramuscularly inoculated with vNDV, VAU – vaccinated uninfected, UNI – unvaccinated infected and UNU – unvaccinated uninfected. At weekly intervals blood was collected from six randomly selected hens in each group for serum calcium and phosphorus assays. Groups VAI and UNI showed a significant (p < .05) drop in egg production. Serum phosphorus levels of groups VAI and UNI were significantly (p < .05) lower than those of groups VAU and UNU. There was a highly positive correlation between serum phosphorus levels and egg production which was highly significant (r = .74; p < .01). The changes in serum calcium levels of infected groups were only slight, and the relationship between serum calcium levels and egg production was low, positive and not significant (r = .26; p > .05). Drop in egg production that occurred in the ND-infected laying hens was positively strongly correlated with the drop in serum phosphorus levels.
Highlights
Newcastle disease (ND) is a viral disease of poultry caused by a single-stranded, non-segmented, negative-sense RNA virus known as avian paramyxovirus serotype 1, belonging to the genus Avulavirus, subfamily Paramyxovirinae within the family Paramyxoviridae, order Mononegavirales (Mayo 2002; Lamb et al 2005)
The objective of this study was to evaluate changes in serum levels of calcium and phosphorus in laying hens infected with velogenic Newcastle disease (ND) virus (vNDV), and correlate these changes with the drop in egg production that occurs in ND
There was a drastic drop in egg production in both infected groups (VAI and VAU) of hens beginning at week 1 post infection (PI), with the egg production of these groups being significantly (p < .05) lower than those of groups VAU and UNU (Table 1)
Summary
Newcastle disease (ND) is a viral disease of poultry caused by a single-stranded, non-segmented, negative-sense RNA virus known as avian paramyxovirus serotype 1, belonging to the genus Avulavirus, subfamily Paramyxovirinae within the family Paramyxoviridae, order Mononegavirales (Mayo 2002; Lamb et al 2005). The disease is worldwide in distribution (Alexander and Senne 2008) and is regarded throughout the world as one of the most important poultry diseases. It causes high flock morbidity and mortality in susceptible birds, leading to serious economic losses (Alexander and Senne 2008). ND outbreaks can cause massive economic damage through control efforts and trade losses (Alexander 2001; Alexander and Senne 2008). ND belongs to the notifiable diseases of list A of the World Organisation for Animal Health (OIE 2013)
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