Pathological consequences of low atmospheric pressure stunning in broiler chickens.

Low atmospheric pressure stunning (LAPS) is a novel approach to pre-slaughter stunning of chickens using progressive hypobaric hypoxia by the application of gradual decompression (280s cycle) according to a set of prescribed pressure curves. Low atmospheric pressure stunning produces a non-recovery state. Concerns have been raised relating to the possible pathological and welfare consequences of expansion of air in the body during LAPS. In a randomised trial, we compared the gross pathology of broilers exposed to LAPS with a control group euthanised by intravenous injection of pentobarbital sodium (60 mixed sex broilers per treatment). The birds were exposed to each treatment in triplets and all birds were subject to necropsy examination to detect and score (1 to 5, minimal to severe) haemorrhagic lesions or congestion for all major organs and cavities (e.g. air sacs, joints, ears and heart) as well as external assessment for product quality (e.g. wing tips). Behavioural data (latency to loss of posture and motionless) and chamber cycle data (temperature, humidity, pressure and oxygen availability) confirmed that LAPS had been applied in a manner representative of the commercial process. All of the organs observed were structurally intact for both treatment groups. No lesions were observed in the external ears, oral cavity, tracheal lumen, crop and air sacs of birds from either treatment group. There was no difference between treatments in the wingtips, nasal turbinates, thymus, biceps femoralis and colon. Haemorrhagic lesions were observed in the calvaria, brains, hearts and lungs of both treatment groups, but lesions in these areas were more severe in the LAPS treatment group. It was not possible to distinguish between pathological changes induced by decompression or recompression. In the barbiturate group, more severe haemorrhagic lesions were observed in the superficial pectoral muscles as well as greater congestion of the infraorbital sinuses, liver, spleens, duodenum, kidneys and gonads. These findings provide evidence that LAPS did not result in distension of the intestines and air sacs sufficient to cause changes, which were grossly visible on postmortem examination. There was also no evidence of barotrauma in the ears and sinuses. The pathological changes observed in the barbiturate treatment were as expected based on barbiturate toxicity. Low atmospheric pressure stunning appears to produce pathological changes by a variety of well-established mechanisms, and while these pathological data have limited value as welfare indicators, the results confirm that organ integrity was not compromised by the process.

Risk factors associated with Salmonella status of broiler flocks delivered to grow-out farms.

In a prospective field observational study in the southeastern USA, we sampled gastrointestinal (GI) tracts from chicks of 65 broiler flocks delivered to conventional grow-out farms for rearing. The flocks were hatched at seven broiler hatcheries. The mean within-flock prevalence of Salmonella-positive samples was 6.5% and ranged from 0% to 86.7%. Of the 65 flocks studied, 25 (38.5%) had at least one Salmonella-positive sample. Accounting for confounding variability among the hatcheries and broiler companies, we tested whether the probability of detecting Salmonella in GI tracts of the chicks delivered was associated with certain characteristics of parent breeder flocks; hatchery production volume; hatchery ventilation system; hatchery egg-room conditions; egg incubation, candling, hatching, eggshell and bird separation, and bird-processing procedures; management of hatchery-to-farm transportation; day of week of hatch; weather conditions during transportation; or season of the hatch. Two risk factor models were adopted. The first model indicated that a greater number of parent flocks, manual separation of eggshell and bird, and a greater amount of fluff and feces on tray liners used during hatchery-to-farm transportation at delivery were associated with increased probability of detecting Salmonella in chick GI tracts, whereas a greater number of birds in the delivery vehicle was associated with decreased probability. The second model indicated that broiler flocks hatched on Tuesdays versus either Mondays or Thursdays (with no hatches on Wednesdays, Fridays or week-ends), increased average hatchability of the eggs from the parent flocks, and greater amounts of fluff and feces on the transport tray liners at delivery were all associated with increased probability of detecting Salmonella in chick GI tracts. The results of this study suggest potential management decisions to lessen Salmonella contamination of broilers supplied by commercial hatcheries and areas for further research.

Risk factors associated with detection of Salmonella in broiler litter at the time of new flock placement.

In this study, we investigated risk factors associated with the probability to detect Salmonella in samples of litter collected within 2 h prior to new flock placement in 76 grow-out houses on 38 conventional broiler farms located in the US states of Mississippi, Alabama and Texas. We evaluated characteristics of location and layout of the farm; area adjacent to and surrounding the house; house construction; condition and type of equipment in the house; litter management and other production, sanitation, visitation and biosecurity practices; non-broiler animal species on the farm; and weather conditions on the 3 days leading up to flock placement. Logistic regression was used to model the relationships between probability to detect Salmonella in litter and potential risk factors. In the screening process, each risk factor was evaluated as a single fixed effects factor in a multilevel model that accounted for variability among the sampled farms and their production complexes and companies. Of almost 370 risk factors screened, 24 were associated with the probability to detect Salmonella in litter. These were characteristics of the surroundings of the house, house construction and conditions, litter management, length of downtimes between flocks in the house, biosecurity and farm location. After investigation of collinearity between these variables and building of models for important risk factor categories, the list of candidate variables for the final model was refined to eight factors. The final model demonstrated that a higher probability of detecting Salmonella in litter was strongly associated with the use of wood to construct the base of the walls or to cover the inside of the broiler house foundation, and with the use of fresh wood shavings to top-dress or completely replace the litter between flocks.

Attempts to reproduce a runting/stunting-type syndrome using infectious agents isolated from affected Mississippi broilers.

Various organisms, including 12 aerobic and 2 anaerobic bacteria, an infectious bronchitis virus (IBV), a reovirus, and 2 bacteriophages, were isolated from intestinal tracts of commercial broiler chicks undergoing a runting/stunting-type condition. In a series of trials, these agents were given alone and in combination to 1-day-old chicks in an attempt to reproduce the field condition. Because the agents were isolated and evaluated over time, an augmented designs variation of the analysis of variance proved particularly useful in analyzing the data collected and minimizing bird usage. Chicks inoculated with tryptose phosphate broth served as negative controls, and those inoculated with the original intestinal tract material were positive controls. Relative to the negative control chicks, body weights of the positive control chicks and of chicks inoculated with several of the agent combinations were depressed at 7, 14, and 21 days postinoculation. Common to combinations that most consistently caused weight depression were reovirus + IBV + others of the agents isolated. However, because none of the agent combinations reproduced the lethargy or dry feces seen in the positive controls, none was considered to be the ultimate cause of this particular runting/stunting-type condition. Further characterization of the disease syndrome was based on the positive control chicks. These chicks consistently had lowered body weights and transient lethargy and dry fecal pellets. Microscopic lesions consisted of lymphocytic renal and pancreatic interstitial infiltrates, dilated or cystic duodenal and jejunal crypts of Lieberkühn, increased crypt depth, and increased cellularity in the intestinal lamina propria. Electron microscopy revealed regular arrays of 26-nm viral particles, usually in association with membrane debris, in intestinal epithelial cells and crypt lumens and in intestinal and renal mesenchymal cells. These viral particles were theorized to be essential to reproduction of the complete malady seen.

Intralesional herpesvirus, reovirus-like particles, and bacteria in a flock of broiler chicks with spiking mortality, diarrhea, and enterotyphlitis.

The search for a solitary cause of spiking mortality (so-called spiking mortality syndrome) among broiler chicks has been thwarted by the fact that multiple agents cause similar mortality histograms. In the present case report, we describe intralesional herpesvirus, reovirus-like virus particles, and bacteria in small and large intestines from chicks with a spiking mortality histogram, diarrhea, and enterotyphlitis. We attributed the spiking mortality histogram to starvation coupled with diarrhea.

Effects of modified-live infectious bronchitis virus vaccines on the head-associated lymphoid tissue (HALT).

Specific-pathogen-free (SPF) leghorn chicks were inoculated with different modified-live infectious bronchitis virus (IBV) vaccines to determine if the vaccines interfered with immune competence of the head region. A total of 16 vaccines were evaluated comprising nine Massachusetts, three Arkansas, two Holland, one Florida, and one combination vaccine (containing both Connecticut and Massachusetts). Chicks were vaccinated when they were 4 weeks, 2 weeks, or 1 day of age. When all chickens were 4 weeks 3 days of age, their glands of Harder (GH) were assayed for the ability to respond to antigenic stimulation. Tissues from chicks given GH-depressing and non-GH-depressing vaccines were also collected and scored for histological changes in the head-associated lymphoid tissue (HALT) sites and the trachea. All 16 vaccines depressed the GH response to antigenic stimulation when given to 4-week-old chicks. Six of these vaccines (two Massachusetts, two Arkansas, and two Holland) also depressed the GH response when given to 2-week-old chicks, and one, an Arkansas vaccine, depressed the GH response when given to 1-day-old chicks. The main histological changes associated with the vaccines were increases in lymphocyte populations in the nasal mucosa, eyelid, and, for some, the lacrimal gland and the GH. In addition, lymphoid follicles were increased in the eyelid, to a lesser degree in the GH, and occasionally in the trachea. No relationship was found between histologic changes and vaccine-induced suppression of the GH response.

Blood glucose values and definitions for hypoglycemia and hyperglycemia in clinically normal broiler chicks.

Two analytical methods were used to establish expected blood glucose values for normal 2-week-old broiler chicks. The lower values (cut-offs) that define hypoglycemia are 137 mg/dl for the standard method and 60 mg/dl for the Chemstrip bG method. The upper cut-offs that define hyperglycemia were 363 mg/dl for the standard method and 280 mg/dl for the Chemstrip bG method. Results from these two tests are significantly (F = 110.9, df = 1/124, P < 0.00001) linear and highly correlated. Results from the present study will allow diagnosticians to make confident diagnoses of hypoglycemia and hyperglycemia in young broiler chicks.

Reovirus associated with excessive mortality in young bobwhite quail.

Multiple submissions of bobwhite quail (Colinus virginianus) were received for diagnosis from a commercial-size quail operation. The history and clinical signs included respiratory distress, lethargy, and substantial mortality. Reovirus was recovered from quail in the first submission, and both reovirus and adenovirus were isolated from later submissions. To determine the pathogenicity of the isolated reovirus, the initial isolate was inoculated into young quail from a different source. Those inoculated by the subcutaneous route became lethargic, and more than half died during the 2 weeks of the trial. Reovirus was recovered from a high percentage of those inoculated by this route. To the authors' knowledge, the isolation of reovirus from quail has rarely been reported, and reovirus has never before been suggested as a pathogen in this species.

Victim emotional response: effects on social reaction to victims of rape.

Two studies examined the impact of variations in a rape victim's emotional reactions on others' perceptions of her. The victim was presented as emotionally expressive or emotionally controlled. In one study written descriptions were used, while in the second, videotape presentations were employed. In both studies, the emotionally expressive victim was rated as more credible. In the videotape presentation, additional differences indicated that the emotionally controlled victim is perceived as having less aversion for the rape and was liked less. Results are discussed in terms of observers' expectations concerning rape victim reactions and the social climate after a rape.