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Newcastle disease outbreaks still occur sporadically in commercial vaccinated flocks and remains a constant threat to poultry producers despite advances in vaccination against the disease. Another aspect that can be a complementary control strategies or that is well recognized but is often neglected is the differences in immune response due to genetic or breed/type variation. This study investigated the immune responses to LaSota vaccination in light weight type or breeds of chickens (pullets) and heavy weight type or breeds of chickens (broilers) used in commercial poultry production. Fifty seven-week-old White Marshall broilers (Br) and 50 Isa Brown pullets (Pu) of the same age were randomly divided into 4 groups viz: vaccinated broilers chickens (VaBr), unvaccinated broiler chickens (UBr), vaccinated pullet chickens (VaPu) and unvaccinated pullet chickens (UPu). Chickens in groups VaBr and VaPu were vaccinated with LaSota vaccine while groups UBr and UPu were not vaccinated. The chickens were observed for clinical signs and lesions. Serum samples were collected from the chickens in all the groups on days 0, 7, 14, 21, 28 post vaccination (PV), and assayed for haemagglutination inhibition (HI) antibodies. The geometrical mean antibody titres (GMT) of the pullets were 2 to 3 times higher than those of the broilers on days 7 to 28 PV. Vaccination produced neither clinical signs nor lesions. The above observations show that naturally pullets produce higher antibodies than broilers, and suggest breedbased variation on immune responses to Newcastle disease vaccination. The knowledge from the present study may lead to genetic approach to vaccine development and development of more effective vaccination strategies to be used in commercial poultry production.

The histology of visceral organs from singed Red Sokoto goats were assessed for reliability for use as histopathological samples from singed abattoir specimen. This becomes important as samples for histopathology and histology of goats in Nigeria have been sourced from singed carcasses, with no available literature reporting on the effect of singeing on the histological appearance of tissues from such sample. Hence, this study will fill this knowledge gap. The unfixed samples post-singeing were grouped into time periods of an hour interval up to 3 hours. They were subsequently fixed after allocated tie framed and processed for histological observation. The slides were graded on a scale of 1 to 3, where 1 referred to highly distorted, 2 referred to moderately distorted and 3 referred to mildly distorted. The samples from unsigned viscera that were fixed immediately served as control. Most of the visceral organs showed moderate distortions, except the intestines which degenerated to highly distorted architecture after 3 hours. The stomach compartments displayed normal organ structure similar to the control samples. Blood extravasations were observed in most of the organs. This project shows that samples from singed carcasses that are fixed within 2 hours post-singeing are stable for histology or histopathological studies. It also implied that abattoir samples for histopathogy should be sent to the nearest laboratory about 2 hours radius for fixation and processing to generate reliable data.Key words: Singeing, organ architecture, fixation, histology, histopathology, Nigeria