Research note: Expert opinions of feather sucking and licking behavior in meat chicken breeder birds.

Feather sucking, or feather licking, has been reported anecdotally by employees in the Australian meat chicken breeder industry, but scarcely in the scientific literature. Consequently, the causes and implications of this behavior in meat chicken breeding chickens is relatively unknown. We surveyed 17 industry experts to generate hypotheses about feather sucking behavior. We aimed to understand the frequency and when it occurs, and attempted to understand what may cause an "outbreak". The recruitment of participants was intentionally biased towards Australian perspectives; only 5 of the 17 participants were international. All participants, except 1, had seen feather sucking/licking behavior (94.1%) and most participants (80%) suggested that the behavior was most frequently observed during rearing. Participants presented varying concerns about this behavior, ranging from the perspective that it was "normal" and had no impact on welfare, to concerns about mating injuries due to damaged feathers, increased risk of feather pecking and cannibalism, and psychological stress indicated by expression of repetitive (seemingly) functionless behavior. "Feather licking," "feather sucking," "feather eating," and "feather pecking" were terms used interchangeably, leading to confusion by participants about the cause and implications of the target behavior. The most common factors reported as the cause were boredom (52.9%), nutritional deficiencies (47.1%), and feed restriction (41.2%) and more than 80% of respondents agreed that stress contributes to feather sucking. The outputs from this study reflect only a small, but expert, number of opinions on feather sucking/licking behaviors in the Australian meat chicken breeder industry. A systematic understanding of this behavior is needed to provide insight into causation and the implications for welfare.

Descriptive epidemiology of smothering in Australian commercial free-range layer hen farms.

Since the early 2000 s the practice of free-range egg production has increased in developed countries, partly driven by consumer perception that free-range housing is better for hen welfare. While poultry in free-range systems have more behavioural opportunities compared with poultry in caged systems, free-range systems are associated with greater frequencies of infectious disease, predation and 'smothering', a condition where birds pile on top of one another with death occurring due to suffocation. Although the frequency of smothering deaths in Australian free-range layer poultry is anecdotally high, there is a lack of empirical evidence quantifying smothering cause-specific mortality rates and identifying factors that place birds at higher risk of death from smothering. This was a prospective cohort study of poultry flocks managed by three commercial free-range layer organisations in Eastern Australia. Flocks were enrolled into the study from 1 January 2019 to 29 March 2021 and were followed until the end of lay or until the end of the study on 31 March 2022, whichever occurred first. Throughout the follow-up period flock managers provided production details for each flock and details of smothering events using custom-designed logbooks.A total of 84 flocks were enrolled in the study: 32 from Organisation 1, 35 from Organisation 2 and 17 from Organisation 3. The number of birds per flock ranged from 16,000 to 45,000. The total mortality rate was 1131 deaths per 10,000 bird-years. Smothering mortality rate across the three organisations was 183 (minimum 133, maximum 223) deaths per 10,000 bird-years at risk. Smothering accounted for around 16% (minimum 9%, maximum 22%) of all deaths.We identified no distinctive temporal pattern in daily smothering risk as a function of either the number of days since placement or calendar date. The locations of smothering events in sheds and in the outdoor range were not consistent, with relatively large numbers of smothering events occurring in specific locations for some sheds but not others. To the best of our knowledge, this study is the largest prospective study of smothering mortality in commercial free-range layer flocks conducted to date. Estimates of smothering incidence rate and how that varies within and between flocks and organisations over time provides a critically important benchmark for further investigations into this substantial area of productivity loss.

Effect of woodchip bedding during wet conditions on feedlot cattle productivity, behaviour and relative adrenal gland weight.

Problems associated with muddy pens have been identified as some of the most serious animal welfare issues related to outdoor feedlot beef production, but there is relatively little work examining the use of woodchip bedding for lot-fed beef cattle under conditions of cold, wet, but non-freezing winters on soil under-bases. This study examined the effects of graded levels of woodchip on the performance and behaviour of feedlot cattle housed in wet pen conditions. Bos taurus steers (n = 300; 379.1 ± 24.1 kg) were blocked by weight and breed and randomly assigned to 30 10-steer feedlot pens provided with either no woodchip bedding (Control, n = 10) manure interface only, or 15 cm depth of woodchip bedding (W15, n = 10) or 30 cm depth of woodchip bedding (W30, n = 10). The steers were housed in these treatment pens for 109 days on a feedlot ration, and the pens were irrigated so that approximately 74 mm of total precipitation (irrigation + natural rainfall) fell onto the pen surface every 30 days. Temperatures were mostly <20 °C maximum and -1 to 5 °C minimum. Steers were weighed on five occasions. Animal position and posture in pen were recorded once a week over an 8-hour day-time period. Carcase characteristics were measured, and adrenal gland weights were recorded. Providing woodchip bedding increased liveweight gain (P < 0.001) and gain:feed (G:F, P = 0.012) after day 28, increased DM intake (DMI) after day 92 (P = 0.049), and increased carcase weight (P = 0.001) and dressing percentage (P = 0.023). There was no additional benefit of W30 over W15 for liveweight gain or DMI, but the benefit of W15 for G:F was lower than that of W30 by the end of the feeding period (P = 0.012). There were no effects of bedding on other carcase quality traits. Steers in Control pens utilised the front of the pen for lying and standing more than the W15 and W30 steers (P < 0.001) suggesting the steers in the Control pens perceived the front of the pen as less aversive, potentially due to increased drainage compared to rest of the pen and proximity to feed bunk. Adrenal gland weight/kg and carcase weight tended to be higher in the Control treatment group than the W30 steers (P = 0.077). This research has demonstrated that for a 109-day feeding period in cold, wet conditions, steer performance and welfare can be improved by providing a minimum of 15 cm woodchip bedding.

Visual access to an outdoor range early in life, but not environmental complexity, increases meat chicken ranging behavior.

Not all chickens access an outdoor range when the opportunity is provided. This may be related to the abrupt change in environments from the stable rearing conditions to the complexity of the outdoor range. We aimed to prepare chickens to range by increasing the complexity of the indoor environment early in life with the intention to encourage range use. Mixed sex Cobb500 chickens were allocated to 1 of 3 treatment groups: visual access (VA) treatment provided VA to the outdoor range from day old via transparent pop-hole covers; environmental complexity (EC) treatment provided an artificial haybale, fan with streamers and a solid vertical barrier; Control treatment was a representative conventional environment. Chickens were given access to the outdoor range at 21 d of age. Behavior in the home pen was assessed in wk 1, 2 and 5 and individual ranging behavior was monitored through radio frequency identification (RFID) technology. The VA chickens were more active compared to EC (P = 0.006) and Control (P = 0.007) chickens and spent more time foraging than control chickens (P = 0.036) during the first week of life. More VA chickens accessed the range area compared to EC chickens (P = 0.015). VA chickens accessed the range sooner after they were first provided access and spent more time on the range than EC and control chickens (P < 0.001). Mortality was lower in the VA treatment compared to EC (P = 0.024) and control group (P = 0.002). There was evidence that VA chickens weighed less than Control and EC chickens, however results were inconsistent between age and sex. Hence, providing meat chickens with VA to an outdoor range early in life increased activity in early life, decreased latency to first access the range and increased time on the range and lowered mortality. Future work should aim to understand the mechanism behind these changes in behavior to develop recommendations for producers to implement in commercial conditions.

Partition of variation for predicting experimental power with a broiler chicken example.

A 1932 editorial in Poultry Science stated that sampling theory, or experimental power, could be useful for "the investigator to know how many … birds to put into each experimental pen." Nevertheless, in the past 90 yr, appropriate experimental power estimates have rarely been applied to research with poultry. To estimate the overall variation and appropriate use of resources with animals in pens, a nested analysis should be conducted. Bird-to-bird and separate pen-to-pen variances were separated for 2 datasets, one from Australia and one from North America. The implications of using variances for birds per pen and pens per treatments are detailed. With 5 pens per treatment, increasing birds per pen from 2 to 4 decreased the SD from 183 to 154, but increasing birds/pen from 100 to 200 only decreased the SD from 70 to 60. With 15 birds per treatment, increasing pens/treatment from 2 to 3 decreased SD from 140 to 126, but increasing pens/treatment from 11 to 12 only decreased the SD from 91 to 89. Choosing the number of birds to include in any study should be based on expectations from historical data and the amount of risk investigators are prepared to accept. Too little replication will not allow relatively small differences to be detected. On the other hand, too much replication is wasteful in terms of birds and resources, and violates the fundamental principles of the ethical use of animals in research. Two general conclusions can be made from this analysis. First, it is very difficult to detect 1% to 3% differences in broiler chicken body weight with only one experiment consistently because of inherent genetic variability. Second, increasing either birds per pen or pens per treatment decreased the SD in a diminishing returns fashion. The example presented here is body weight, of primary importance to production agriculture, but it is applicable whenever a nested design is used (multiple samples from the same bird or tissue, etc.).

Frequent range visits further from the shed relate positively to free-range broiler chicken welfare.

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.

Population ageing and social expenditure in Australia.

Questions concerning the impact of demographic aging on the dependency burden in Australia are examined. "This article shows that the social expenditure to GDP ratio is heavily dependent on assumptions made about real spending growth, productivity growth, unemployment and participation rates. It produces a framework that makes the assumptions underlying the projections clear and enables the results of changing the assumptions to be easily compared. The projected ratios are significantly higher than those obtained in previous Australian studies."

CD28 delivers a costimulatory signal involved in antigen-specific IL-2 production by human T cells.

CD4+ T cells require two signals to produce maximal amounts of IL-2, i.e., TCR occupancy and an unidentified APC-derived costimulus. Here we show that this costimulatory signal can be delivered by the T cell molecule CD28. An agonistic anti-CD28 mAb, but not IL-1 and/or IL-6, stimulated T cell proliferation by tetanus toxoid-specific T cells cultured with Ag-pulsed, costimulation-deficient APC. Furthermore, the ability of B cell tumor lines to provide costimulatory signals to purified T cells correlated well with expression of the CD28 ligand B7/BB-1. Finally, like anti-CD28 mAb, autologous human APC appeared to stimulate a cyclosporine A-resistant pathway of T cell activation. Together, these results suggest that the two signals required for IL-2 production by CD4+ T cells can be transduced by the TCR and CD28.

A monoclonal antibody specific for a cytochrome c T cell stimulatory peptide inhibits T cell responses and affects the way the peptide associates with antigen-presenting cells.

A monoclonal antibody (mAb) specific for the 93-104 segment of pigeon cytochrome c (cyt) was shown to block interleukin 2 production and proliferation by pigeon cyt-specific T cells in response to the pigeon cyt 81-104 peptide using either the LK35.2 B cell hybridoma or normal splenocytes as antigen-presenting cells (APC). The mAb inhibited the response to soluble peptide antigen presented by metabolically inactive paraformaldehyde-fixed APC but not the response to APC that were pre-pulsed with Ag. These results suggest that the mAb blocked the formation of peptide-major histocompatibility complex (MHC) class II molecule complexes at the cell surface but did not displace the peptide once bound to the MHC class II molecule. As determined by direct binding experiments using labeled peptide, the major means of free peptide association with live APC was fluid-phase endocytosis. No free peptide associated directly with the MHC class II molecule at the cell surface near 0 degrees C since APC pulsed with peptide on ice did not activate cyt-specific T cells. The mAb enhanced the association of the radiolabeled peptide with APC at 4 degrees C apparently by binding of the peptide-mAb complex to Fc receptors. By stripping molecules from the LK35.2 cell surface using a nonspecific protease it was shown that the peptide-mAb complexes were not internalized either at 4 degrees C or 37 degrees C. Since the mAb was found to stably bind the peptide at pH levels below that of endosomes (pH 5.5-6.2) even if the peptide-mAb complexes were taken up by fluid-phase endocytosis, it is likely that the peptide would not be able to associate with MHC class II molecules inside the APC. This mAb appears to inhibit T cell activation by blocking the formation of peptide-MHC class II molecule complexes at the cell surface and by interfering with uptake of the peptide into endosomes. Therefore, it is different from other antibodies that have been reported to block T cell receptor recognition of preformed peptide/MHC class II molecule complexes.

Selectivity and patch measurements of A-current channels in Helix aspersa neurones.

1. The ionic selectivity of A-current K+ channels has been measured in single Helix aspersa neurones by recording the reversal potential shift in test solutions containing various monovalent cations. 2. The A-current channel is permeable to Tl+, K+, Rb+, NH4+ and Cs+. The channels may also be sparingly permeable to Na+ and Li+. Organic cations have an apparent small permeability as judged from their reversal potentials, but this may be an artifact of K+ accumulation. 3. A large patch electrode (3 microns tip) isolated a region that appeared to contain only A-current channels. This may indicate that A-current channels are found in the membrane as rafts of at least 3 microns in diameter. 4. The single-channel conductance calculated from single-channel current steps was 14 pS.

The effect of leakage on micro-electrode measurements of intracellular sodium activity in crab muscle fibres.

The effect of lowering extracellular Na (Nao) on the intracellular Na activity has been measured in single muscle fibres from the crab Carcinus maenas using Na+-sensitive glass micro-electrodes. Measurements have been made with recessed-tip micro-electrodes inserted radially into intact fibres, and with axial electrodes in cannulated fibres. Reducing Nao to one-tenth normal caused local contractions in intact fibres. The apparent steady-state internal Na (Nai) and the fall in Nai when Nao was reduced were found to vary considerably not only between different fibres but also when measured with different electrodes in the same fibre. The steady-state Nai, and the extent and rate of its decrease when Nao was reduced, could be reduced by pushing the Na+-sensitive electrode deeper into the fibre. Cannulated fibres generally had higher internal Na activities than intact fibres, but at comparable levels of Nai the rate of fall recorded from cannulated fibres when Nao was reduced was much slower than with intact fibres. In both intact and cannulated fibres the decrease in Nai was reduced by ouabain. The level of Nai recorded in cannulated fibres was sensitive to depolarization. Depolarizations from -50 to -30 mV resulted in a rise in Nai while further depolarization to 0 mV resulted in a fall in Nai. We conclude that both our results and those of Vaughan-Jones (1977) on undissected fibres are contaminated by leakage into the fibre round the micro-electrode. The true internal Na activity is probably much lower than previously reported.

Respiratory distress in newborn infants: contribution to current mortality.

A review of infants with respiratory distress born at the Mercy Maternity Hospital, Melbourne, during the years from 1975 to 1977 showed that live-born infants totalled 13304; 288 (2.2%) had respiratory distress. Of the 13304 infants, 197 died; 75 (38.1%) were infants with respiratory distress. Hyaline membrane disease was the cause of the respiratory distress in 153 (53.1%) infants; 58 (37.9%) infants with that problem died. Hyaline membrane disease accounted for 58 (77.3%) of the 75 deaths in infants with respiratory distress. Assisted ventilation was required in 147 (51.0%) infants with respiratory distress and chronic complications of its use acceptable as bronchopulmonary dysplasia occurred in only 8.2% and retrolental fibroplasia in only 3.4%; it is suggested that assisted ventilation was commenced too late in 23 (34.0%) infants. Twenty-eight (42.0%) infants with respiratory distress died despite correct usage of assisted ventilation. This number attests to the dangers of prematurity; hence the decision to deliver an infant prematurely should not be taken lightly.