Some aspects of the microbiology of poultry foods
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Date
1968
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Thesis
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Abstract
This investigation was undertaken in an attempt to find an explanation for diseases of unknown etiology occurring among chickens in New Zealand. Within the poultry industry, opinions were expressed of the importance of such diseases, particularly the so-called 'Q' disease, and it was felt that considerable economic losses were sustained. Because in recent years, toxins of fungal origin have been implicated as causal agents of a number of diseases of previously unknown etiology, it was felt that a study of the fungi present on poultry mashes in this country would be of value in providing evidence for or against mycotoxins as the cause of some unexplained diseases of chickens. In New Zealand there has already been a considerable amount of work done on mycotoxins. The disease known as facial eczema, which affects sheep and cattle, and is of great economic importance, was worked on in this country. It was found to be caused by a fungal toxin present in fodder ingested by the affected animals.
In this project, before the effects of fungi on the health of young chickens were studied, the microbial population of poultry foodstuffs as a whole was examined. Micro-organisms in mashes and components of mashes were enumerated by the plate count technique. Bacteria in poultry foodstuffs were identified to generic level. A separate study was made of the incidence of Salmonella spp. because of the economic importance of Salmonellae to the poultry industry.
The fungi isolated from poultry foodstuffs were studied in greater detail than the bacteria. The dominant genera of fungi which occurred on mashes and their components were determined. Fungi isolated were identified as far as possible.
Once preliminary work was completed, biological assays were carried out. The effects of dosing young chickens with fungal extracts were studied; the fungi tested having been isolated originally from poultry foodstuffs. In some cases, feeding trials were also carried out. The effects of fungal extracts on other biological systems were studied, sterile extracts being added to healthy cultures of chicken embryo fibroblasts, and injected into developing chicken embryos. These techniques provided a more rapid method of screening extracts for toxicity than the dosing and feeding trials.
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