الفهرس 
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Abstract
A survey study was carried out to identify and to estimate the effects of Mycoplasma gallisepticum, Salmonella typhymurium and E. coli (APEC) on performance of 15 commercial egg -layer flocks .In addition, a field study for monitoring the efficacy of some commercially available disinfectants on Mycoplasma gallisepticum, Salmonella typhymurium, E. coli (APEC ) and microbial load of the floor house in commercial egg- layer flocks in Egyptian farms, with different application methods. The selected disinfectants were; Formalin, Phenol, QAC, Halamid, Virkon S and Micro Sept M. The results showed that: (1) the incidence of M. gallisepticum in the flocks 33.3 % the mortalities rates at the end of 78 weeks of age was 12% and also, the current egg-production and performance significantly reduced (P < 0.05). (2) MG isolate accessed on Gen-Bank and coded as; MZ826700, 26 bp DNA linear BCT 30-SEP-2021. (2) The incidence of Salmonella typhymurium; the isolation of Salmonella typhymurium (hfq gene of Salmonella typhimurium) from 5 flocks (33.7 %) out of 15 flocks, the mortalities rates at the end of 78 weeks of age was 16 % and also, the current egg-production, average egg weight, hen housed day, hen housed egg and percent peak of egg-production were: 68 %, 59.2 gm, 68.4%, 318, 78% and 70%, respectively. (3) the incidence of E. coli in the observed commercial egg-layer flocks; the isolation of E. coli (APEC of rfbO157 gene ) from 4 commercial egg-layer flocks (26.7 %) out of 15 flocks, the mortalities rates at the end of 78 weeks of age was 20% and also, the current egg-production, average egg weight, hen housed day, hen housed egg and percent peak of egg-production were: 69.2%,58.3 gm, 70%,326,78% and 69%,respectivel. (4)Fogging increased the efficacy of the disinfectants for 15 min contact of exposure time and showed a highly significance reduction of Mycoplasma gallisepticum, Salmonella typhymurium and E. coli (APEC of rfbO157 gene) populations. (5) Disinfectants effects did not significantly influence total aerobic bacterial populations at the low application rate except in case of Formalin and Virkon’S, and affect significantly on aerobic bacteria, yeast and mold populations at the high application rates (P < 0.05). Cold fogging resulted in the greatest effect on aerobic bacteria, yeast and mold populations. Ultra-low volume (ULV) fogging machines are cold fogging machines that use large volumes of air at low pressures to transform liquid into droplets that are dispersed into the atmosphere. This type of fogging machine can produce extremely small droplets with diameters ranging from 1–150 μm. The size of the droplet is very important as each application has an optimal droplet size. The optimum droplet sizes are between 5 and 20 μm.
The droplets that are created are of such a small size that less carrier for the formulation is required to cover the required surface area. The best way to understand the concept of using less formulation to cover a larger surface area is to look at the mathematical side of the scenario. In the case where the diameter of a droplet is reduced to half its original size then the number of droplets that can be formed from the same volume of formulation will increase eightfold. If the droplet diameter is reduced to 10 percent of its original size, then the number of droplets that can be formed will increase a thousand-fold. In this way the droplet diameter determines the amount of droplets that will form.