In mid-2000, a broiler chicken company in Alabama experienced high early mortality rates in chicks from two different hatcheries. Five isolates of Pseudomonas aeruginosa, obtained from these contaminated hatcheries and resulting broiler chicks with omphalitis, were selected to determine virulence of the bacteria. One-day-old specific-pathogen-free white leghorn chicks were placed into positive pressure isolation units (10 chicks per unit); feed and water were provided ad libitum. The five isolates of P. aeruginosa (1 x 10(1) or 1 x 10(1) colony-forming units/bird) were used to challenge two replicates of 10 chicks via yolk sac inoculation. Two control groups were injected with 0.1 ml of phosphate-buffered saline, and two groups received no treatment. Mortality was recorded daily, and the chicks that died were necropsied and liver and yolk sacs were cultured. After 14 days, the remaining chickens were euthanatized and necropsied. Bacterial isolates retrieved from liver and yolk sacs were identified by the API 20 NE typing system to confirm that they were the same as the challenge isolate. Virulence varied greatly among the isolates, resulting in mortality rates from 0 to 90%. The challenge isolates produced different and often distinctive postmortem lesion patterns. Antibiotic sensitivity tests showed that all five isolates were resistant to sulfisoxazole, ceftiofur, penicillin, lincomycin, bacitracin, oxytetracycline, erythromycin, naladixic acid, and tetracycline. The isolates varied in sensitivity to other antibiotics, but all isolates were sensitive to gentamicin.
The effect of lysine deficiency on chicken immune function was evaluated using broiler chickens fed a diet with lysine at 67% of the control diet (1.24% lysine). The evaluation of humoral immune function was conducted by measuring the antibody production to a live Newcastle disease virus (NDV) vaccination using the hemagglutination inhibition (HI) test and enzyme-linked immunosorbent assay (ELISA). The cellular immune function was evaluated through the use of cutaneous basophil hypersensitivity test. The antibody response to NDV vaccination was reduced in broiler chickens fed a lysine-deficient diet when measured by ELISA but not when measured by HI. The cell-mediated immune response was also reduced by lysine deficiency.
Extended posthatch holding (in the hatcher) has been reported to dehydrate chicks, reduce broiler performance, and depress immune response. Nevertheless, some commercial hatcheries are increasing incubation time in an attempt to minimize possible bacterial contamination of incompletely healed navels. The objectives of this study were to determine the effects of posthatch holding on broiler performance and the effects of bird density and additive stress on performance and immune response. Twelve hundred broiler eggs (58 to 70 g) were incubated. Chicks were removed from the hatcher after 528 h of incubation, banded, and weighed. Half of the chicks were returned to the hatcher for an additional 24 h (HELD). Both hatcher treatments were placed at two densities (.07 and .12 m2 per bird). Individual BW were taken at 21 and 43 d of placement and 43 d of age. The HELD chicks weighed significantly less than controls at time of placement. At 21 d postplacement the HELD broilers were significantly heavier than controls, but were similar by 43 d. Total feed conversion was not affected in the HELD treatment, but birds in the .07 m2 per bird density were less efficient in terms of total feed conversion. Chick holding time and density seemed to affect antibody titers at 5 wk. Although holding chicks in the hatcher for 24 h did not clinically dehydrate chicks or affect performance, it decreased immune response. In addition to less efficient growth, birds in the more crowded pens had depressed immune response.
Concern by consumers about food safety has resulted in increased pressure on poultry companies to develop effective sanitation programs. Salmonella isolates in hatcheries are often the same species isolated from processing plants. Resistance develops in bacteria after prolonged exposure to disinfectants. The methods available in published literature to detect the efficacy of disinfectants are labor intensive and do not consider how bacteria behave when adhered to a solid surface. We used a recently developed technique, which utilizes the actual surfaces on which the disinfectant is to be applied, to evaluate the degree of resistance to four commercially available disinfectants of 17 bacterial isolates from poultry hatcheries. We found that bacterial isolates within the same genus and species have different sensitivities to the same disinfectant. In addition, disinfectants with similar but not identical chemical formulations have different efficacies against the same bacteria.
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