Gordon Memorial Lecture. Chicken anaemia virus--a glimpse of the future?

Assessment of turkey vehicle container microclimate on transit during summer season conditions

This study evaluated the formed microclimate commercial truck transport practices effects on the turkeys' welfare by measuring Dead on Arrival (DOA) index and pale, soft, and exudative (PSE-like) meat occurrence. The experimental design was entirely randomized in a 6 × 2 factorial arrangements (two truck container compartments × six water shower groups) with birds positioned at superior front (SF), inferior front (IF), superior middle (SM), inferior middle (IM), superior rear (SR), and inferior rear (IR) and two bath treatments: with water shower (WiS) and without water shower (WoS) with eight replications for each treatment. The animals were transported for 95 min' journey from the farm to the slaughterhouse under hot-humidity conditions. The results shown herein indicated the formation of a thermal core at the inferior middle and rear truck container regions, because the heat produced by the birds and the influence of developed microclimate consisting of temperature, relative humidity, and air ventilation. The IM and IR container compartments under the WoS treatment presented the highest (P < 0.01) numbers of PSE-like meat incidence and DOA index values compared with those located at the front under WiS treatment as the consequence of the altered to birds unbearable conditions within the container microclimate in transit. The formed microclimate during the commercial transport practices under hot-humidity conditions affected the bird's welfare consequently turkey meat qualities.

Chicken anaemia virus evades host immune responses in transformed lymphocytes

Chicken anaemia virus (CAV) is a lymphotropic virus that causes anaemia and immunosuppression in chickens. Previously, we proposed that CAV evades host antiviral responses in vivo by disrupting T-cell signalling, but the precise cellular targets and modes of action remain elusive. In this study, we examined gene expression in Marek's disease virus-transformed chicken T-cell line MSB-1 after infection with CAV using both a custom 5K immune-focused microarray and quantitative real-time PCR at 24, 48 and 72 h post-infection. The data demonstrate an intricate equilibrium between CAV and the host gene expression, displaying subtle but significant modulation of transcripts involved in the T-cell, inflammation and NF-κB signalling cascades. CAV efficiently blocked the induction of type-I interferons and interferon-stimulated genes at 72 h. The cell expression pattern implies that CAV subverts host antiviral responses and that the transformed environment of MSB-1 cells offers an opportunistic advantage for virus growth.

Pathological manifestations observed in dead-on-arrival broilers at a Danish abattoir

1. The mortality of broilers during pre-slaughter handling, including harvesting and transport, is an issue of increasing public concern which has led to the adoption of Council Directive EC/43/2007 implementing abattoir surveillance regarding the number of dead-on-arrival (DOA) broilers. 2. Pathological lesions and causes of death of DOA broilers at a Danish abattoir were investigated in a cross-sectional study comprising 300 DOA broilers (25 broilers from each of 12 randomly selected flocks). Major pathological manifestations of DOA broilers included severe pulmonary congestion (51.5%), lung congestion in combination with trauma (12.5%), trauma (10.2%), nephropathy accompanied by dehydration and/or discolouration (8.8%), morbus cordis (2.0%), septicaemia (1.7%) and suspected septicaemia (1.0%). Lung congestion accompanied by circulatory disturbances in other tissues was suggested to be due to suffocation. 3. Analyses of pathological diagnoses revealed that DOA broilers can be divided into two main categories, lung congestion and trauma, based on the chronicity of the lesions, both of which are primarily related to management and handling procedures. Most DOA broilers examined (74.2%) were estimated to have died as a consequence of events during pre-slaughter handling underlining the importance of increased focus on handling-related factors to reduce DOA rate.

Broiler trailer thermal conditions during cold climate transport

Burlinguette, N. A., Strawford, M. L., Watts, J. M., Classen, H. L., Shand, P. J. and Crowe, T. G. 2012. Broiler trailer thermal conditions during cold climate transport. Can. J. Anim. Sci. 92: 109–122. Thermal environments within broiler transport vehicles are dependent on ambient conditions and, if poorly managed, can be a welfare concern. To effectively manage broiler transport, the environmental conditions throughout vehicles must be understood. Under standard commercial practices, temperature and humidity levels in double-trailer broiler vehicles were examined for a range of ambient temperatures (−24 to 11°C). During warmer ambient conditions (9.8°C) trailer roof vents and side curtains were all open, which resulted in a narrowing of the on-board temperature range (10.3 to 16.7°C). As ambient temperature cooled side curtains and some of the roof vents were closed. This resulted in increasingly variable and more extreme thermal conditions, with heat and moisture accumulated along the midline of the load near the front of the lead trailer and near the back of the rear trailer. At an ambient temperature of −22.1°C trailer temperatures ranged from −20.7 to 21.7°C with an estimated 58.6% of the load volume being exposed to temperatures below 0°C. In addition, the trailer humidity ratio rose 14.0 g kg−1 above ambient and conditions approached saturation (RH>80%) in 55.2% of the load volume. These results support the need to find a means to remove moisture and redistribute heat on broiler trailers during cold ambient conditions.

Relationship between maximum daily temperature and mortality of broiler chickens during transport and lairage

1. Based on records of all (n = 59 171 843) broiler chickens slaughtered over three years at one processing plant, the overall mortality of birds in transit was 0.126%. 2. There was a pronounced seasonal effect with increased mortality in the summer months, particularly June, July and August. Mortality increased when the maximum daily temperature (measured in the shade) rose above about 17 degrees C at the start of the summer. 3. Between 17.0 and 19.9 degrees C, mortality was 30% higher than at lower temperatures. Between 20.0 and 22.9 degrees C it increased 2.6-fold, and at temperatures of above 23 degrees C 6.6-fold. There was no evidence of birds dying from hypothermia at very low ambient temperatures (down to -1 degrees C). 4. The implication from the results is that above a maximum daily temperature of 17 degrees C steps may need to be taken to ameliorate the damaging effects of transport on bird welfare.

Site-directed mutagenesis of the VP2 gene of Chicken anemia virus affects virus replication, cytopathology and host-cell MHC class I expression

Chicken anemia virus (CAV) is an immunosuppressive pathogen of chickens. To further examine the role of viral protein 2 (VP2), which possesses dual-specificity protein phosphatase (DSP) activity, in viral cytopathogenicity and its influence on viral growth and virulence, an infectious genomic clone of CAV was subjected to site-directed mutagenesis. Substitution mutations C87R, R101G, K102D and H103Y were introduced into the DSP catalytic motif and R129G, Q131P, R/K/K150/151/152G/A/A, D/E161/162G/G, L163P, D169G and E186G into a region predicted to have a high degree of secondary structure. All mutant constructs were infectious, but their growth curves differed. The growth curve for mutant virus R/K/K150/151/152G/A/A was similar to that for wild-type virus, a second cluster of mutant viruses had an extended latent period and a third cluster of mutant viruses had extended latent and eclipse periods. All mutants had a reduced cytopathogenic effect in infected cells and VP3 was restricted to the cytoplasm. Mutation of the second basic residue (K102D) in the atypical DSP signature motif resulted in a marked reduction in virus replication efficiency, whereas mutation of the first basic residue (R101G) attenuated cytopathogenicity, but did not reduce replication efficiency. Expression of major histocompatibility complex (MHC) class I was markedly downregulated in cells infected with wild-type CAV, but not in those infected with mutants. This study further demonstrates the significance of VP2 in CAV replication and shows that specific mutations introduced into the gene encoding this protein can reduce virus replication, cytopathogenicity and downregulation of MHC I in infected cells.