Selected highlights from other veterinary journals
Measuring space requirements of broiler chickens
E. A. M. Bokkers, I. J. M. de Boer, P. Koene
THERE is continuing debate about the space requirements of broiler chickens. This study aimed to measure the amount of floor area a broiler occupies when displaying different behaviours and to estimate the number of birds that can be kept per square meter.
Fast growing broilers were housed in eight floor pens (1.25 by 0.8 m) from one to 42 days of age. Birds were housed at either a low (eight birds per pen) or high (16 birds per pent) stocking density. Cameras positioned above the pens were used to make video recordings of the birds over four consecutive days when the broilers were six weeks old (general time of slaughter). Overhead screenshots taken of birds showing particular behaviours (dustbathing, walking, stretching, idle, drinking, ground pecking and preening) were used to measure the amount of floor area occupied by their bodies. Data were entered into two models to compute the space needed per bird performing a behaviour in relation to flock size, and to compute stocking density based on synchronisation of behaviour and body space.
Posture and density were found to affect body space when broilers were idle, drinking or ground pecking. The first model showed that the maximum number of broilers that could be housed was 15.3 to 15.7 birds/m2 (37.8 to 38.7 kg/m2), based on low-density measurements, and 18.5 to 19.4 birds/m2 (45.7 to 47.9 kg/m2), from high-density measurements. The second model showed that the maximum number of broilers that could be housed was 13.7 to 15.9 birds/m2 (33.8 to 39.2 kg/m2), based on low-density measurements, and 15.4 to 18.6 birds/m2 (38.0 to 45.9 kg/m2), from high-density measurements.
On the basis of the results, the authors conclude that stocking density in large flocks should not exceed 16 birds/m2 (39.4 kg/m2). They add that greater stocking densities might lead to compression of birds, suppressing opportunities for behavioural expression and impairing welfare.
Early immune response to foot-and-mouth disease virus infection in cattle
M. A. Windsor, B. V. Carr, B. Bankowski, D. Gibson, E. Reid, P. Hamblin, S. Gubbins, N. Juleff, B. Charleston
THIS study examined the early innate and adaptive immune response to foot-and-mouth disease (FMD) virus infection in cattle.
Six Holstein-Friesian cattle were exposed for 24 hours to one of two cattle that had been challenged intradermolingually with a FMD serotype O viral strain. Blood and serum samples were collected for haematology, quantitative RT-PCR for virus detection, virus-neutralising antibody testing and liquid-phase blocking ELISA. Interferon type 1 (IFN-1) activity was measured using a promoter-reporter gene assay, and interleukin type 10 (IL-10) levels were measured by ELISA. Blood samples were tested in proliferation assays using a variety of antigens, including pokeweed mitogen, inactivated FMD virus antigen, mock infected BHK-21 cell lysate and heat inactivated bovine herpesvirus antigen.
Viraemia was detected between two and four days after cattle were placed in contact with challenged animals. Typical clinical signs were observed in all cattle from days 2 to 4 postinfection, and viraemia was resolved by day 7. All animals seroconverted to FMD virus, had detectable neutralising antibodies seven days after challenge, and were considered to have protective titres (>45) by 14 days after challenge. These results were consistent with previous reports. In contrast to previous studies in pigs, cattle did not develop leucopenia, and the proliferative responses of peripheral blood mononuclear cells to either mitogen or third-party antigen were not suppressed. Low levels of IFN-1 and IL-10 were detected in the circulating sera.
The authors conclude that the results suggest there was no generalised immunosuppression during the acute phase of FMD virus infection in cattle.
Testing for feline leukaemia virus in cats from an area of low antigen prevalence
J. A. Beatty, S. Tasker, O. Jarrett, A. Lam, S. Gibson, A. Noe-Nordberg, A. Phillips, A. Fawcett, V. R. Barrs
MOLECULAR techniques have demonstrated that cats may harbour feline leukaemia virus (FeLV) provirus in the absence of antigenaemia. This study used a number of serological and molecular techniques to look for evidence of infection with FeLV in cats from an area of low antigen prevalence.
Peripheral blood samples were obtained from three groups of cats in Australia: sick, in-contact, and young, healthy cats. Data on signalment, environment, source and feline immunodeficiency virus vaccination status were recorded. The sick group included 75 cats that presented at a veterinary clinic over a seven-month period with anaemia or another cytopenia or with intermediate or high-grade lymphoma. The in-contact group contained four free-ranging cats from a multi-cat household that had been in contact with a persistently antigenaemic cat (in which FeLV was confirmed by isolation) during the previous 12 months. The young group included 169 healthy cats aged up to one year, which were presented for routine procedures at one of three inner city veterinary clinics over a 12-month period. Peripheral blood samples were obtained and tested using quantitative real-time PCR for FeLV, p27 ELISA, anti-feline oncornavirus-associated cell-membrane-antigen (FOCMA) antibody testing, and virus isolation.
Two of the 75 cats with cytopenias or lymphoma were found to be transiently positive for provirus. In one other cat, anti-FOCMA antibodies were the only evidence of exposure. In the 169 healthy cats, all test results were negative. In contrast, three of the four in-contact cats showed evidence of infection.
The authors conclude that the results support a role for factors other than FeLV in the pathogenesis of cytopenias and lymphoma. They add that, in regions of low prevalence, where the positive predictive value of antigen testing is low, quantitative PCR may assist with diagnosis.
- British Veterinary Association