S06 AF July August 2017 Poultry 01_Layout 1 28/07/2017 17:09 Page 22
AFRICAN POULTRY SUPPLEMENT
Maintaining high standards of hygiene in eggs set for hatching can play a major role in producing healthier and higher quality chicks. Dr Terry Mabbet explores good poultry practices that can ensure better hygiene and high yield in poultry farms.
Hygiene management for high hatch numbers
Treatment of hatching eggs is essential to control shell-borne infections in hatched chicks. (Photo: Franz12/Shutterstock)
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OOD POULTRY PRACTICE is often a matter of common sense and none more so than health and hygiene measures required for high hatchability of healthy chicks. All else being equal, the cleaner the eggs set for hatching in the incubator, the better are the results achieved as healthier and higher quality chicks. The science is simple. Pathogenic bacteria, which can never be totally eliminated from poultry practice, respond rapidly to the warm and humid conditions in the incubator. The bird’s egg is designed to exclude pathogenic microbes but also to allow free gaseous exchange as the chick embryo respires, grows and develops. This requires
Sub-standard hygiene can reduce hatchability by up to 15 per cent. 22 African Farming - July/August 2017
a porous calcium carbonate shell to allow oxygen to diffuse in and carbon dioxide to diffuse out. But egg shell pores are potential weak points through which bacteria can enter to disrupt and destroy developing chick embryos. Sub-standard hygiene can reduce hatchability by up to 15 per cent but is easily avoided by using common-sense on-farm measures that may be as simple as collecting floor eggs separately from nest eggs. Microbial contamination of hen’s eggs can occur congenitally or extra-genitally. Congenital contamination invariably happens in the ovary and involves a range of well-known pathogenic microorganisms including salmonella bacteria, mycoplasmas and certain virus particles. These egg transmitted pathogens are controlled by vaccination, blood testing and subsequent removal of infected hens or in the case of mycoplasmas, the use of antibiotic egg dipping.
Extra-genital contamination is something that happens after the egg is laid and which typically causes rots, mould growth, bangers (eggs that explode once inside the incubator), early dead chick embryos and a higher first-week on-farm chick mortality, the latter often being the result of yolk sac infection. Eggs laid-on and collected from the floor will be the most heavily contaminated by potentially pathogenic microbes and therefore most at risk. Evolution of the egg, complete with membranes and a hard and inert but porous calcium carbonate egg shell has furnished the embryo with a comprehensive system of protection for unimpeded growth and development and successful hatching of the free living chick. The eggshell has thousands of pores that are sufficiently large to permit bacterial cells and fungal spores to pass through and enter the egg. Passage through most of these pores is prevented by the presence of
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