ABSTRACT
A total of 54 broiler flocks during the first two weeks of life was used to investigate the incidence of avian pathogenic E. coli in Egypt; 28 isolates (51.85%) were revealed by colony morphology and biochemical identification which then investigated for their serogroups and only 18/28 isolates were serotyped. The most prevalent serotypes were O115, O142, O158, O55, O125, O114, O27, O20, and O15. By application of polymerase chain reaction (PCR), 83.3% (15/18) of the serotyped isolates were confirmed to be E. coli, and 93.3% (14/15), 46.6% (7/15), and 20% (3/15) of isolates harbored the iss, iutA, and fimH genes, respectively. Virulence testing of the selected 13 APEC isolates on the specific-pathogen-free (SPF) chicks revealed them to be highly virulent (15.4%), moderately virulent (23.1%), and avirulent (61.5%); however, all isolates (100%) were extremely virulent towards SPF embryonated chicken eggs. Antibiotic resistance (100% of isolates (n = 13)) was observed for ampicillin, amoxycillin-clavulanic acid, and tetracyclines, colistin (92.31%; 12/13), doxycycline and spiramycin (84.62%; 11/13), florfenicol (69.23%; 9/13), cefotaxime (61.54%; 8/13), and ciprofloxacin (53.85%; 7/13). The highest percentage of sensitivity (53.85% of isolates; 7/13) was recorded for ofloxacin and enrofloxacin followed by gentamycin (46.15%; 6/13). The results suggest that the diagnosis of APEC with PCR is rapid and more accurate than traditional methods for E. coli identification; moreover, the presence or absence of iss, iutA, and/or fimH genes is not an indicator of in vivo pathogenicity of APEC. Thus, further studies, including a wider range of virulence genes and gene sequencing, are required. In addition, serotyping has no effect on the virulence of APEC.
ABSTRACT
The objective of this work was to evaluate the effects of varying levels of chromium propionate on blood biochemistry and growth performance of broilers (1-35 days). Five diets were formulated by using chromium propionate with inclusion levels of 0, 200, 400, 800 and 1600 ppb. A total of 300 broilers were divided into 5 groups with 6 replicates of 10 birds in each under completely randomized design. The starter feed intake remained unaffected (p > 0.05) whereas finisher and overall feed intake was different (p < 0.05) among different experimental groups. Feed conversion ratio and weight gain in starter, finisher and overall improved significantly (p < 0.05) with the increasing levels of chromium propionate. Blood glucose was decreased (p < 0.05) with increasing dietary chromium level. Chromium supplementation did not affect antibodies titers against NDV and AIV-H9. Neither live, hilal, after skin removal, eviscerated, chest weight and legs with shanks weight nor liver and heart weights were affected (p > 0.05) while gizzard weight reduced significantly (p < 0.05) due to supplementation of chromium. On the basis of results, it may be concluded that chromium propionate supplementation improved weight gain and FCR and reduced blood glucose. However, better performance and weight gain may be achieved if chromium propionate is added at the rate of 400 ppb in broiler diets.
