Following the ban of all food animal growth-promoting antibiotics by Sweden in 1986, the European Union banned avoparcin in 1997 and bacitracin, spiramycin, tylosin and virginiamycin in 1999. Three years later, the only attributable effect in humans has been a diminution in acquired resistance in enterococci isolated from human faecal carriers. There has been an increase in human infection from vancomycin-resistant enterococci in Europe, probably related to the increased in usage of vancomycin for the treatment of methicillin-resistant staphylococci. The ban of growth promoters has, however, revealed that these agents had important prophylactic activity and their withdrawal is now associated with a deterioration in animal health, including increased diarrhoea, weight loss and mortality due to Escherichia coli and Lawsonia intracellularis in early post-weaning pigs, and clostridial necrotic enteritis in broilers. A directly attributable effect of these infections is the increase in usage of therapeutic antibiotics in food animals, including that of tetracycline, aminoglycosides, trimethoprim/sulphonamide, macrolides and lincosamides, all of which are of direct importance in human medicine. The theoretical and political benefit of the widespread ban of growth promoters needs to be more carefully weighed against the increasingly apparent adverse consequences.

Background: Conventional broilers are currently one of the most efficient protein converters. Although decades of progress in genetic selection and feed formulation have lead to high standards of efficient broiler production, still a lot of variability is found between farms and between successive flocks. The aim of this study was to investigate risk-and/or protective factors for poor health and performance in conventional broiler-farms in Europe by developing eight multivariable linear mixed models. Three different models were used to investigate mortality (overall, first week, after first week), three models for performance variables (growth, feed conversion, European production index) and two models were related to slaughterhouse data (i.e. dead on arrival and condemnation rate). Results: Several factors related to management and housing were significantly associated with health and performance of broilers. The following factors were associated with increased mortality: floor quality, neonatal septicemia, ventilation type and other professional activities of the farmer. The factors associated with performance were chick sex, coccidiosis infections, necrotic enteritis, dysbacteriosis, light intensity adaptations, ventilation type, comparing daily flock results with previous flock results by farmer, daily check of feed and water system and type of feed. For dead on arrival three risk factors were identified i.e. daily growth, type of light adaptation and type of drinkers system. For condemnation rate seven risk factors were found, i.e. type of drinking system, daily growth, feed withdrawal time, type of ventilation, house size, septicemia after seven days and type of feed. Conclusions: These results imply that a multifactorial approach is required with adaptations involving both improvements in management, housing, health programs and an increasing level of professionalism of the farmer in order to improve broiler performance and health.

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This short communication reports on the isolation of QX-like infectious bronchitis virus (IBV) from the proventriculus of broiler chicken in England, and its pathogenesis in specific-pathogen-free (SPF) chicks. This appears to be the first report of the isolation of this virus from the proventriculus of affected chicks in the UK. The virus was first recovered from this tissue in chickens in China in 1996 (YuDong and others 1998), and later, more cases were reported, including in flocks vaccinated against IBV (Yu and others 2001). We received samples of kidney and proventriculus from a flock of 56-days-old commercial broiler chickens, where the submitting field veterinarian reported respiratory signs, increased levels of mortality, a poor feed conversion ratio and suboptimal live body weight gain. At necropsy, proventriculitis and swollen kidneys were reported. Similar tissues were pooled and processed for IBV detection by reverse-transcriptase PCRs (RT-PCR), as previously described (Worthington and others 2008), and virus isolation (VI) were attempted. RT-PCR tests on the supernatant of the pooled tissues of kidneys were negative for IBV, while the proventriculus samples were positive. The proventriculus was negative for avian metapneumovirus (aMPV), Newcastle disease virus (NDV) and infectious bursal disease virus (IBDV), but positive for fowl adenovirus by PCR tests. Subsequent sequencing of the IBV showed that it closely resembled a vaccinal strain belonging to IBV 793B. Since the flock had been vaccinated with a 793B-type vaccine two weeks prior to the sampling, it was likely that residual genome of the vaccine was detected. The tissue supernatant was subjected to VI, both in tracheal organ cultures (TOC) and embryonated chicken eggs (ECE).

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