2020, Taylor, P S, Hemsworth, P H, Groves, P J, Gebhardt-Henrich, S G, Rault, J-L

Little is known about the implications of accessing an outdoor range for broiler chicken welfare, particularly in relation to the distance ranged from the shed. Therefore, we monitored individual ranging behaviour of commercial free-range broiler chickens and identified relationships with welfare indicators. The individual ranging behaviour of 305 mixed-sex Ross 308 broiler chickens was tracked on a commercial farm from the second day of range access to slaughter age (from 16 to 42 days of age) by radio frequency identification (RFID) technology. The radio frequency identification antennas were placed at pop-holes and on the range at 2.7 and 11.2 m from the home shed to determine the total number of range visits and the distance ranged from the shed. Chickens were categorised into close-ranging (CR) or distant-ranging (DR) categories based on the frequency of visits less than or greater than 2.7 m from the home shed, respectively. Half of the tracked chickens (n=153) were weighed at 7 days of age, and from 14 days of age their body weight, foot pad dermatitis (FPD), hock burn (HB) and gait scores were assessed weekly. The remaining tracked chickens (n=152) were assessed for fear and stress responses before (12 days of age) and after range access was provided (45 days of age) by quantifying their plasma corticosterone response to capture and 12 min confinement in a transport crate followed by behavioural fear responses to a tonic immobility (TI) test. Distant-ranging chickens could be predicted based on lighter BW at 7 and 14 days of age (P=0.05), that is before range access was first provided. After range access was provided, DR chickens weighed less every week (P=0.001), had better gait scores (P=0.01) and reduced corticosterone response to handling and confinement (P<0.05) compared to CR chickens. Longer and more frequent range visits were correlated with the number of visits further from the shed (P<0.01); hence distant ranging was correlated with the amount of range access, and consequently the relationships between ranging frequency, duration and distance were strong. These relationships indicate that longer, more frequent and greater ranging from the home shed was associated with improved welfare. Further research is required to identify whether these relationships between ranging behaviour and welfare are causal.

2021, Ahaduzzaman, Md, Groves, Peter J, Walkden-Brown, Stephen W, Gerber, Priscilla F

Salmonellosis, caused by Salmonella spp., is a widely reported foodborne zoonosis frequently associated with ingestion of poultry products. Salmonella vaccination of chickens can be used to reduce bacterial shedding and risk of human infection. To determine Salmonella burden in chicken farms, culture methods of environmental samples that require a turn-around time of 5-7 days are usually used. Rapid screening using molecular assays such as PCR of pre-enriched broth has been reported for Salmonella spp. detection in feed, floor dust, and drag swabs within 2-3 days. Here we report an adaptation of the method for detection of Salmonella in poultry dust samples collected using a settle plate method under experimental conditions. Key features:

• Passive dust sample collection using dry settle plates without media suspended from dropper lines of drinkers.
• Small amount of sample required for the pre-enrichment process.
• Quantification of Salmonella DNA with high sensitivity using an inexpensive extraction protocol.

2022-10, Habte, Tadiose, Gerber, Priscilla F, Ibrahim, Fozia, Groves, Peter J, Walkden-Brown, Stephen W

In Ethiopia, most chicken disease outbreaks and mortalities are attributed to a respiratory syndrome known as “fengil” with variable clinical signs and undefined etiology. The main goal of this study was to determine whether key respiratory pathogens that could contribute to the fengil syndrome circulate in Ethiopia. Specifically, we aimed to determine the seroprevalence of infectious laryngotracheitis virus (ILTV), infectious bronchitis virus (IBV), Newcastle disease virus (NDV), Mycoplasma gallisepticum (Mg), and avian metapneumovirus (aMPV). A cross-sectional survey was conducted in 158 scavenging and 42 small and medium-scale intensive chicken holdings in the East, West and North Shewa Zones of central Ethiopia. Blood from 495 chickens was collected and serological tests were used to determine exposure to these pathogens. Vaccination against NDV was the only immunization practiced with a significantly higher vaccination rate in the intensive than the scavenging system. Serological evidence of a high level of exposure to all pathogens was detected, including the first report on the seroprevalence of aMPV, ILTV, and IBV in the East Shewa Zone. The chicken and holding seroprevalence rates were respectively 91% and 94% for IBV, 34% and 57% for aMPV, 47% and 66% for Mg, 27% and 51% for ILTV and in unvaccinated flocks, 39% and 53% for NDV. These pathogens could contribute to the fengil syndrome, commonly ascribed to NDV. The seroprevalence of aMPV and ILTV was higher in chickens under the scavenging system. Exposure to multiple pathogens was common, with more than 50% of chickens positive for three or more pathogens in the scavenging system. This was reflected in significant positive associations between seropositivity to ILTV, Mg, ILTV, and IBV. The role of these pathogens in the causation of respiratory disease in the field requires further investigation.

2017-07-20, Taylor, Peta S, Hemsworth, Paul H, Groves, Peter J, Gebhardt-Henrich, Sabine G, Rault, Jean-Loup

Little is known about broiler chicken ranging behaviour. Previous studies have monitored ranging behaviour at flock level but whether individual ranging behaviour varies within a flock is unknown. Using Radio Frequency Identification technology, we tracked 1200 individual ROSS 308 broiler chickens across four mixed sex flocks in two seasons on one commercial farm. Ranging behaviour was tracked from first day of range access (21 days of age) until 35 days of age in winter flocks and 44 days of age in summer flocks. We identified groups of chickens that differed in frequency of range visits: chickens that never accessed the range (13 to 67% of tagged chickens), low ranging chickens (15 to 44% of tagged chickens) that accounted for <15% of all range visits and included chickens that used the range only once (6 to 12% of tagged chickens), and high ranging chickens (3 to 9% of tagged chickens) that accounted for 33 to 50% of all range visits. Males spent longer on the range than females in winter (p < 0.05). Identifying the causes of inter-individual variation in ranging behaviour may help optimise ranging opportunities in free-range systems and is important to elucidate the potential welfare implications of ranging.

2019-09, Nguyen, Trong V, Ahaduzzaman, M, Campbell, Dana L M, Groves, Peter J, Walkden-Brown, Stephen W, Gerber, Priscilla F

Monitoring of Marek's disease virus (MDV) and infectious laryngotracheitis virus (ILTV) genome using poultry dust can be useful to monitor on-farm vaccination protocols but there are no set guidelines for collection of this sample type. This study assessed different dust collection methods for MDV and ILTV detection in a vaccinated layer flock (n = 1700) from day-old to 50 weeks of age. Birds were vaccinated against MDV at day-old, and ILTV by drinking water at week 6 and eye drop at week 12. Dust samples were collected weekly by settle plates (1-3 plates/15 m ²) or by scraping surfaces in the poultry shed and tested for ILTV and MDV genomic copies (GC) by PCR. ILTV GC were detected 4 weeks post water vaccination, peaked at weeks 12-14 and became mostly undetectable after week 18. MDV was detected in dust on week 1, peaked at weeks 3-6, declined 3 logs by week 26 and remained detectable at this level until week 50. There was no difference in the detection rates of ILTV and MDV collected from settle plates in different locations of the shed (P>0.10). There was no difference between settle plate and scraped samples in ILTV GC load but higher MDV GC were found in scraped samples. The settle plate method appears to reflect the current level of vaccine virus in the flock while the scrape method likely represents a cumulative record of shedding. Assessment of viral GC in dust samples is a good candidate for a practical method of estimating successful vaccine administration.

2022-09-26, Groves, Peter J, Assen, Awol M, Etherington, Ashley, Stillman, Mark, Alfirevich, Sheridan, Gerber, Priscilla F, Langfield, Alex-Kate, Walkden-Brown, Stephen W

Context. Drinking water vaccination of young meat chickens with Infectious Laryngotracheitis (ILT) vaccine is problematic. Vaccine failure and adverse vaccine reactions are frequently reported. Variations in the technique of applying ILT vaccines by this mass vaccination method need to be understood to contribute to improving the success of vaccination.

Aims. This study aimed to examine variations in the techniques of application of Infectious Laryngotracheitis vaccines via drinking water for young meat chickens.

Methods. Drinking water vaccination techniques were observed and recorded across 52 broiler flocks during ILT outbreaks in three geographic areas of Australia. Descriptive statistics for all variables were computed and variations between integrator company procedures were statistically compared.

Key results. Despite rigorous standard operating procedures, wide variations were observed in time of water deprivation prior to vaccination (3–15 min), time drinking water was stabilised prior to addition of vaccine and the type of stabiliser product used, time to activate the flock following filling of the water lines with vaccine (10–127 min), time for the vaccine to be consumed (36–226 min) and the volume of drinking water per bird used to provide the vaccine (11–48 mL/bird).

Conclusions. Variation in vaccination technique can affect the success of drinking water vaccination against ILT in young meat chickens.

Implications. Understanding the importance of the variable factors in vaccine application method can improve the success of water vaccination against ILT.

2009, Islam, Afm Fakhrul, Walkden-Brown, Steve W, Groves, Peter John, Wells, Ben

An experiment was conducted to develop and optimize a chicken bioassay to detect the presence of infective viral pathogens in poultry litter from a variety of sources. The experiment also aimed to determine the effect of type of chickens and age of exposure to litter on the level of viral infectivity. The bioassay detected chicken anaemia virus, infectious bursal disease virus and fowl adenovirus from chicken litters. SPF chickens showed higher sensitivity than commercial broiler chickens without any effect of age of exposure, however, the assay was more sensitive in broiler chickens when exposed at day 8. We conclude that the bioassay based on exposure of day-old SPF chickens is a viable assay of viral infectivity of poultry litter.

2001, Islam, Afm Fakhrul, Walkden-Brown, Steve William, Wong, Chun Wai, Groves, Peter John, Burgess, Susan, Arzey, KE, Young, P

'In ovo' vaccination against Marek's disease is a widely used technology in the broiler industry.A series of experiments was carried out to determine the site of vaccine deposition in the egg during automated 'in ovo' vaccination, and the effect of vaccine deposition site and dose on vaccine responses following vaccination with cell-associated herpesvirus of turkeys in commercial broiler chickens. Vaccine deposition site following automated 'in ovo' vaccination was principally influenced by the age of embryo, with egg size having a smaller effect. The frequency of vaccine deposition inside the embryo body increased as incubation progressed from day 17.5 to 19.5. In experiments using manual vaccine deposition intra-embryonically (IE) or extra-embryonically (EE) at day 18.5, EE vaccine deposition resulted in a significantly delayed development of post-vaccinal viraemia relative to both IE vaccination and subcutaneous vaccination at hatch. There were no effects of vaccine dose (2000, 4000 or 8000 plaque forming units) on the timing of post-vaccinal viraemia. The timing of post-vaccinal viraemia was found to be a good indicator of the level of protection provided by the vaccine against challenge with earlier viraemia associated with better protection. IE vaccine deposition induced significantly greater protection than EE deposition against challenge with a virulent strain of Marek's disease virus. IE deposition consistently produced a high level of protection (68 to 84%) irrespective of vaccine dose or challenge day, while EE vaccine deposition produced no or low levels of protection (0 to 27%) depending on the vaccine dose and day of challenge. The growth of challenged chickens was also affected by site of vaccine deposition, with significantly higher live weights at day 56 of age in IE compared with EE vaccinated groups. These data suggest that the site of vaccine deposition within the embryo is an important determinant of the success of 'in ovo' vaccination.

2015, Taylor, P, Hemsworth, P H, Dawkins, M S, Groves, P, Rault, J-L

The demand for free-range chicken meat in Australia is increasing. Free-range products are usually perceived as more welfare friendly by consumers (Department for Environment Food and Rural Affairs, 2011) and particularly fulfill the belief that the ability to perform natural behaviour leads to better welfare. However, there is a lack of scientific knowledge relative to the use of the outdoor range by broilers and its implications, advantages or disadvantages, in terms of bird behaviour and welfare. Therefore this study investigated behavioural time budgets of broiler chickens on two Australian commercial farms. Behaviour was monitored inside the shed and in four range areas, differing in resource availability (tree, shade cloth or no resource present) and distance from the shed (adjacent to the shed wall or 7.5m from the shed). Results indicated that distance is a deterrent for range use, as few broiler chickens were seen in areas 7.5m from the shed. Furthermore, behavioural time budgets differed between broiler chickens observed in the shed compared to those in the range; there was more active, exploratory and vigilant behaviours seen in the range and more resting and comfort behaviors observed in the shed. However the implications of such behavioural differences remain unknown.

2003, Islam, Afm Fakhrul, Groves, Peter John, Walkden-Brown, Steve William, Arzey, K E, Burgess, Susan

Automated 'in ovo' vaccination (IOJ) against Marek's disease in broiler chickens is now a routine practice in the poultry industry. This method deposits vaccine mostly into the extra-embryonic (EE) spaces around the embryo, principally the amnion. In earlier experiments of ours, manual EE (MEE) vaccine deposition has not produced good protection in contrast to the apparent efficacy of the automated 'in ovo' method. Two experiments are reported, one confirming this difference in protection and the other demonstrating that there are significant differences in the precise site of vaccine deposition between the two methods, with a higher incidence of allantoic deposition in the case of MEE (25.5%) compared to OIJ (5.7%). However, this finding alone cannot explain the difference in protection between the two methods. We suggest that different methods of vaccinal virus uptake from the amnion may be involved.