The effects of long (C20/22) and short (C18) chain omega-3 fatty acids on keel bone fractures, bone biomechanics, behavior, and egg production in free-range laying hens.

Keel fractures in the laying hen are the most critical animal welfare issue facing the egg production industry, particularly with the increased use of extensive systems in response to the 2012 EU directive banning conventional battery cages. The current study is aimed at assessing the effects of 2 omega-3 (n3) enhanced diets on bone health, production endpoints, and behavior in free-range laying hens. Data was collected from 2 experiments over 2 laying cycles, each of which compared a (n3) supplemented diet with a control diet. Experiment 1 employed a diet supplemented with a 60:40 fish oil-linseed mixture (n3:n6 to 1.35) compared with a control diet (n3:n6 to 0.11), whereas the n3 diet in Experiment 2 was supplemented with a 40:60 fish oil-linseed (n3:n6 to 0.77) compared to the control diet (n3:n6 to 0.11). The n3 enhanced diet of Experiment 1 had a higher n3:n6 ratio, and a greater proportion of n3 in the long chain (C20/22) form (0.41 LC:SC) than that of Experiment 2 (0.12 LC:SC). Although dietary treatment was successful in reducing the frequency of fractures by approximately 27% in Experiment 2, data from Experiment 1 indicated the diet actually induced a greater likelihood of fracture (odds ratio: 1.2) and had substantial production detriment. Reduced keel breakage during Experiment 2 could be related to changes in bone health as n3-supplemented birds demonstrated greater load at failure of the keel, and tibiae and humeri that were more flexible. These results support previous findings that n3-supplemented diets can reduce fracture likely by increasing bone strength, and that this can be achieved without detriment to production. However, our findings suggest diets with excessive quantities of n3, or very high levels of C20/22, may experience health and production detriments. Further research is needed to optimize the quantity and type of n3 in terms of bone health and production variables and investigate the potential associated mechanisms.

Evaluation of the microclimate in poultry transport module drawers during the marketing process of end-of-lay hens from farm to slaughter.

Changes in module drawer temperature and relative humidity were monitored for 24 commercial loads of hens. Mathematical models revealed significant differences in predicted drawer temperature depending on their location and the outside environmental temperature. Higher predicted temperatures were found in uppermost drawers of the top modules at the front of the lorry, and lower temperatures in drawers on the outer sides of modules and in those drawers in modules next to the back of the lorry in both the upper and lower modules during transport. In the lairage, drawer temperature generally decreased, except in drawers at the top of modules where temperatures increased. Temperature increases were most often recorded in modules which had been located at the rear of the lorry, which were generally cooler during transport. End-of-lay hens would appear to be exposed to a greater risk of cold stress rather than heat stress in the UK. Inspection of birds during transport, or upon arrival, should be directed to the bottom and side drawers of a load when looking for cold stress, and the top row of drawers (centre) of the top modules when looking for heat stress. The frequency of inspections should increase at times of high ambient temperature while the birds are being held in lairages. Adjusting the numbers of birds loaded per drawer according to bird condition and weather appears to be an effective mitigation strategy which is already in use commercially.

Impact of a mixed chain length omega-3 fatty acid diet on production variables in commercial free-range laying hens.

1. Previous studies found beneficial effects on the prevalence of keel fractures and bone health in laying hens receiving a short chain ω3 fatty acid diet. However, subsequent work using a mixed short and long chain ω3 diet (MCD) found little benefit to bone health and substantial production losses. 2. The current study examined commercial use of a mixed chain length ration in multiple farms and flocks and identified a detrimental effect on productivity including: mortality, number of poor quality eggs, hen daily average, feed consumption, and increased egg weight. 3. Production data were acquired from 11 flocks housed on 5 farms and modelled using MlwiN, a statistical package developed for analysis of hierarchical data. Production responses were individually modelled with duration of exposure to the diet, age of introduction, flock size and farm, included as prediction variables. 4. Analysis indicated birds receiving the MCD manifested dramatic increases in mortality, poor quality eggs, mean egg weight, feed consumption and decreased production in comparison to control flocks receiving a standard ration. Increased exposure time appeared to increase the magnitude of the diet effect. 5. Although no data were collected to explain the potential mechanisms of this diet, the authors discuss several possible scenarios including excessive long chain ω3 content overwhelming eicosanoid regulatory capacity and changes in behaviour patterns.

Levels of mortality in hens by end of lay on farm and in transit to slaughter in Great Britain.

The average mortality for end of lay hens dead on arrival (DOA) was 0.27 per cent (median 0.15 per cent) in a survey of 13.3 million hens transported during 2009. A statistical model of the data indicated main risk factors for DOA to be slaughter plant, distance travelled and external air temperature, with longer journeys and low external air temperatures increasing the risk. Other highly significant risk factors (P<0.001) related to the condition of the birds on farm, where an increased risk of DOA was positively associated with poor feather cover, lower body weight, cumulative mortality of the flock and poor health (indicated by a high proportion of the load rejected at the plant for traumatic injury and disease state). However, the data indicate that by taking risk factors into consideration it is possible to transport hens up to 960 km with low losses in temperate conditions. Mean levels of on-farm mortality, during the laying period, for a total of 1486 flocks were significantly lower in cages (5.39 per cent) than in barn (8.55 per cent), free-range (9.52 per cent) or organic flocks (8.68 per cent) according to producer records a median of seven days before depopulation, with considerable variation between flocks in all systems.

Pop hole use by hens with different keel fracture status monitored throughout the laying period.

The aim of this work was to study the effect of keel fractures on the extent to which free-range hens access the range through pop holes. Over two consecutive laying periods (two production years) a total of 1100 individual birds from one half of a house, divided into four separated flocks, were caught at 25, 35, 45, 55 and 65 weeks, palpated to assess the prevalence and severity of keel fractures and tagged with RFID transponders. Their use of pop holes was subsequently monitored in some cases from week 25 to end of lay at 68 to 70 weeks. At regular intervals (every 10 weeks), the tagged birds were re-caught to assess changes in keel fracture prevalence and severity. The average percentage of birds with fractured keels at 25, 35, 45, 55, 65 and at end of lay (68 to 70 weeks of age) was 5.5, 25.5, 49, 63, 66.5 and 78.5, respectively, across both production years. The effect of keel score on pop hole use was modelled statistically, adjusting for weather conditions and age of the birds. There were significant effects of most of the weather variables recorded, as well as age of the bird, on use of pop holes and also a significant effect of keel score. Higher keel scores resulted in a reduction in pop hole use. A significant statistical interaction between keel score and ambient temperature revealed an accelerated reduction in use as the temperature decreased and keel score increased. It is concluded that the occurrence of keel fractures may affect the birds' ability or willingness to utilise the outdoor range provided by free-range housing systems, thereby reducing the potential welfare advantages of this type of housing.

Use of radiography to identify keel bone fractures in laying hens and assess healing in live birds.

The aim of this study was to use radiography to assess and characterise naturally occurring keel bone fractures in laying hens and monitor live birds over several weeks to examine the healing process. Twenty-four Lohmann brown commercial laying hens with varying degrees of keel bone fracture were used in the study. Birds were radiographed regularly over six weeks and the radiographic features and changing appearance of keel bone fractures were evaluated. The radiographic characteristics of old and new fractures were categorised and indicated that 80 per cent of birds entering the study with new fractures had healed after 35 days and five birds had incurred new fractures irrespective of their original fracture status.

Continuous monitoring of pop hole usage by commercially housed free-range hens throughout the production cycle.

Free-range laying hens are able to move between the indoor house and range through exits termed pop holes. The aim of this study was to examine the proportion of the flock that used the pop holes and to identify patterns of movement throughout the flock cycle. Four flocks of free-range hens each of 1500 birds were studied. Ten per cent of each flock were tagged with RFID (radio-frequency identification) transponders and their pop hole activity studied throughout the production cycle. Within two weeks of tagging at 25, 35, 45, 55 and 65 weeks of age, approximately 80 per cent of the tagged birds were seen in the pop holes and 50 per cent of the tagged birds were seen on 80 per cent of the days available to them after tagging. Within the flock, subpopulations of birds could be identified: those that never ventured to the pop holes (approximately 8 per cent), those that used the pop holes very infrequently (approximately 8 per cent), those that sat in the pop holes (approximately 4 per cent), and those that used the pop holes frequently (approximately 80 per cent). There was an effect of age of the birds, time of day and daily mean temperature on pop hole usage. Additional factors affecting activity on particular days were wind speed, rainfall and hours of sunshine. The findings show that a significant proportion of the flock accesses the pop holes on a regular basis with only a very small proportion preferring to stay in the house.

Influence of housing system and design on bone strength and keel bone fractures in laying hens.

The main objectives of the study were to provide an accurate assessment of current levels of old breaks in end-of-lay hens housed in a variety of system designs and identify the important risk factors. Sixty-seven flocks housed in eight broad subcategories were assessed at the end of the production period. Within each flock, the presence of keel fractures was determined and the tibia, humerus and keel bones dissected for measurement of breaking strength. For each house, variations in internal design and perching provision were categorised and the effective heights of the differing structures recorded. All systems were associated with alarmingly high levels of keel damage although variation in mean prevalence between systems was evident with flocks housed in furnished cages having the lowest prevalence (36 per cent) despite also having significantly weaker bones and flocks housed in all systems equipped with multilevel perches showing the highest levels of damage (over 80 per cent) and the highest severity scores.

Prevalence and factors associated with it, of birds dead on arrival at the slaughterhouse and other rejection conditions in broiler chickens.

1. Standardised data on husbandry were recorded for a flock of birds in one house on each of 150 broiler farms in the UK during the 4 d prior to slaughter. 2. For each flock, the incidence of birds found dead on arrival (DoAs) and the Meat Hygiene Service carcase rejection records were recorded at the slaughterhouse. 3. The mean percentage of birds in each flock found DoA was 0.12% (range 0-0.64%) and the mean percentage of Total Carcase Rejects (TCRs) for each flock was 1.23% (range 0.07-5.51%). 4. A general linear model was developed to examine factors associated with flock percentage DoAs. Assuming a linear relationship, all other factors remaining the same, a one percentage point (PP) increase in small/emaciated birds will result in a 0.155 PP increase in DoAs and a 1 PP increase in wheat in diet 4 will result in a 0.003 PP decrease. An increase by one in the total number of vaccines administered will cause a 0.029 PP decrease in DoAs, a 1 g increase in live weight at slaughter will be associated with a 0.000043 PP increase and a 1 PP increase in mortality on farm would be associated with a 0.000044 PP increase. A 1 PP increase in Ross birds decreases DoAs by 0.0004 PPS: there is also a seasonal effect. 5. The model developed for flock percentage TCRs found that a 1 PP increase in wheat in diet 3 will result in a 0.052 PP decrease in TCRs and a 1 PP increase in Ross birds will cause a 0.009 PP decrease. A 1 PP increase in birds culled on farm will be associated with a 0.03 PP increase in TCRs and the diagnosis of disease during the flock cycle increases TCRs by 0.397 PPs. A one day increase in age at slaughter will result in a 0.046 PP increase in TCRs.

Factors affecting the prevalence of foot pad dermatitis, hock burn and breast burn in broiler chicken.

1. Standardised data on flock husbandry were recorded on 149 broiler farms during the 4 d prior to slaughter. 2. Birds were examined at the slaughterhouse for contact dermatitis lesions. Foot pad dermatitis score (FPDS) and hock burn score (HBS) were measured on five point scales. Carcase rejection data were also collected. 3. The mean percentage of birds in each flock with: moderate or severe foot lesions was 11.1% (range 0-71.5%); moderate or severe hock burn was 1.3% (range 0-33.3%); and, breast burn was 0.02%. 4. A general linear model was developed to examine factors associated with mean flock FPDS. Assuming a linear relationship, within the range of data collected and with all other factors remaining the same, every 1% increase in the proportion of Genotype A birds in the flock was associated with an increase in mean FPDS of 0.003, every one-point increase in litter score was associated with a 0.326 increase in mean FPDS and every one-point increase in flock mean HBS was associated with a 0.411 increase in mean FPDS. Flock mean FPDS was associated with feed supplier and was higher in winter. 5. The general linear model developed for flock mean HBS, found that every one-point increase in mean FPDS increased mean HBS by 0.090, every one-point increase in litter score increased HBS by 0.119 and, every 1% increase in small/emaciated birds decreased mean HBS by 0.333. Reduced HBS was also associated with increased final litter depth, younger slaughter age and an increased percentage of dietary wheat. For every 1% increase in Genotype A birds, a decrease in flock mean HBS of 0.003 would be expected. 6. An effect of hatchery was also identified.

Comparison of the effects of fan-assisted and natural ventilation of vehicles on the welfare of pigs being transported to slaughter.

A total of 417 pigs with an estimated average liveweight of 91 kg were transported to slaughter in three journeys, carried out in late June, each consisting of a three-hour drive followed by a one-hour holding period at the slaughter plant before they were unloaded. The pigs were accommodated on the lower two decks of a three-deck articulated lorry, each deck having five equal-sized pens; half were kept in naturally ventilated pens and half in pens with fan-assisted ventilation. The pigs' body temperature was recorded as the temperature of the blood lost at exsanguination, and as the temperature of the inner surface of the ear measured by thermal imaging. The pigs carried on the upper deck were hotter than those carried on the lower deck, and the pigs carried at the front of the vehicle were hotter than those at the back. There were small differences between the temperatures of the pigs in the different pens, but overall the temperatures of the pigs kept in pens with fan-assisted ventilation were no lower than those of the pigs kept in pens with natural ventilation. The higher temperature of the pigs transported in the front of the vehicle was associated with significantly higher serum concentrations of cortisol and activities of creatine kinase, and a tendency to higher albumin concentrations and osmolality, suggesting that they may have been exposed to more physical and psychological stress, and were possibly slightly more dehydrated, than the pigs in the rearmost pens. The type of ventilation had no effect on the blood composition of the pigs.

Effects of stocking density, flock size and management on the welfare of laying hens in single-tier aviaries.

Management practices, stocking rate and flock size may affect laying hen welfare but there have been few replicated studies in commercial non-cage systems that investigate this. This study used a broad range of physical and physiological indicators to assess the welfare of hens in 36 commercial flocks. Six laying period treatments were examined with each treatment replicated 6 times. It was not possible to randomly allocate treatments to houses, so treatment and house were largely confounded. Three stocking rates were compared: 7 birds/m(2) (n = 2450), 9 birds/m(2) (n = 3150) and 12 birds/m(2) in either small (n = 2450) or large (n = 4200) flocks. In addition, at 12 birds/m(2), in both small and large flocks, birds were subjected to either standard (SM) or modified (MM) management. MM flocks had nipple drinkers and no nest-box lights. Bone strength, fracture incidence, heterophil:lymphocyte (H:L) ratio, live weight, organ weights, serum creatine, serum osmolality, muscle pH and faecal corticosterone were measured on samples of birds at the end of the rearing period and at the end of lay. During the laying period, mortality, production and integument condition were recorded at regular intervals. Birds housed at 9 birds/m(2) had higher mortality than birds housed at 12 birds/m(2) by the end of lay, but not higher than birds housed at 7 birds/m(2). Birds housed at 7 and 9 birds/m(2) had lower percent liver weight, and worse plumage condition than most of the 12 bird/m(2) treatments. Modified management tended to improve plumage condition. There were no clear effects of flock size on the welfare indicators recorded. At the end of the rearing period fracture incidence was almost negligible and H:L ratio was within a normal range. By the end of lay fracture incidence was 60% and H:L ratio was high, with no treatment effect for either measure. This, together with information on faecal corticosterone, feather loss and mortality, suggests that the welfare of birds in all treatments was relatively poor by the end of lay.

Preliminary study to examine the utility of using foot burn or hock burn to assess aspects of housing conditions for broiler chicken.

1. Eleven broiler chicken farms, representing 4 production system types, were visited during the last 5 d of the flock cycle: bird and flock details were recorded. Litter friability was assessed at 9 sites within the house, atmospheric ammonia was measured at three sites and bird cleanliness was assessed on a numerical rating scale. 2. For these flocks, hock burn, foot burn and breast burn were measured at the processing plant by standardised assessors. 3. Significant correlations were identified between the percentage of birds with foot burn and average litter score, average house ammonia concentrations and feather score. 4. No correlation was found between the percentage of birds with hock burn or breast burn and average litter scores, average ammonia concentrations or feather score. 5. No correlation was found between stocking density and foot burn, hock burn or breast burn.6. If confirmed, these findings may have implications for the draft EU Broiler Directive, for which it is proposed that permitted stocking density on farm may be determined by the incidence and severity of contact dermatitis measured on plant.

Estimating the body temperature of groups of pigs by thermal imaging.

Measurements on 28 pens of pigs containing 384 animals to be slaughtered at a commercial abattoir showed that the mean ear temperatures of the pigs in each pen, measured with a thermal imaging camera, were significantly correlated (r=0.71, P<0.001) with the mean temperature of the blood the pigs lost at exsanguination. In measurements on 220 pigs in 16 of the 28 pens, the mean activity of serum creatine kinase was positively correlated with the mean ear temperature (r=0.55, P<0.05) and the mean concentration of serum cortisol was positively correlated with the mean blood temperature (r=0.50, P<0.05), suggesting that the hotter pigs were suffering from a higher level of stress.

The response of pigs to being loaded or unloaded onto commercial animal transporters using three systems.

Groups of pigs were subjected to three different systems of loading and unloading to and from commercial animal transporters. The systems under trial were: the use of a hydraulic tail-lift, a tail board ramp at an angle of 18 degrees and a modular system. The module was a container 2 m x 2.4 m x 1 m high into which the pigs were loaded. The module could then be lifted on and off the lorry with a fork lift truck. Non-invasive monitoring techniques were used to study the responses of the pigs. A subjective handling score, time taken to load and unload, skin temperature, heart rate and salivary cortisol were recorded. Loading and unloading were subjectively assessed as being easiest and quickest using the modular system, which also appeared to be less physically demanding for the animals, as evidenced by lower heart rate and a reduced maximum heart rate. However, with the modular system, elevated cortisol was found during the loading, unloading and resting periods. This could be interpreted as indicating that the pigs were unable to settle in the module and suffered some small degree of stress, which might become more of a problem during prolonged transport. Of the other two systems, there appeared to be little difference between the hydraulic tail-lift and the ramp.

Investigation of palpation as a method for determining the prevalence of keel and furculum damage in laying hens.

Old breaks of the keel and furculum were identified by palpation in 500 end-of-lay hens from 10 flocks housed in free-range and barn systems, and the results were compared with the results obtained by a full dissection and inspection. The method was considered to be sufficiently precise to be used as a diagnostic tool although people using it would need to be trained. The results obtained by dissection indicated that 50 to 78 per cent of the birds in the flocks had breaks of the furculum and keel, but no other breaks of bones were detected.

Defaecation and weight of the gastrointestinal tract contents after feed and water withdrawal in broilers.

1. Broilers were held under constant light for up to 24 h with access to feed and water, access to water only, or access to neither feed nor water. 2. Birds given continuous access to feed ate evenly over the 24-h period. Feed deprivation reduced drinking behaviour to about half of that when feed was available. Deprivation of feed, or of feed and water, had similar effects on defaecation and the reduction in the weight of the gut contents. It reduced the overall number of defaecations over the 24-h period to about 40% of that in birds given food and water, and the weight of the contents by about 75%. The maximum effect of deprivation on defaecation was seen after about 4 h, and on gut contents weight after about 12 h. 3. With longer fasting the contents of most parts of the gut, except the caeca, became wetter. 4. The findings may have implications for the practice of preslaughter food withdrawal to reduce the potential for soiling of the live birds and contamination of the carcase after slaughter. However, the likelihood is that relatively short overall feed deprivation times of not more than 8 to 12 h before killing may be desirable, but specifying firm recommendations on optimal feed withdrawal times requires further work.

Cleanliness of broilers when they arrive at poultry processing plants.

An eight-point photographic scale from 1 (very clean) to 8 (very dirty) was used to assess the cleanliness of the plumage of 69,783 live broiler chickens delivered in 54 loads to three processing plants which were each visited in spring, summer and winter. There were considerable variations between the plants and between the visits, but most birds were given scores of 6 or 7. The average plant scores were 6.07, 6.56 and 6.84, which were associated with frequencies of birds with scores of 7 or more of approximately 38, 56 and 73 per cent. There was some indication that longer feed-withdrawal times of up to 10 hours were associated with dirtier birds.

Behaviour and welfare of individual laying hens in a non-cage system.

1. A leg band containing a transponder was fitted to 80 birds in a perchery containing 1,000 birds. 2. The transponder emitted a unique identification number when a bird walked on one of 8 flat antennae on the floor. The recording apparatus was used to measure the amount of time that each of the tagged birds spent on the slatted and littered areas in a 6-week period. 3. Some birds spent long periods of time on the slats, possibly as a means of avoiding repeated attacks. Duration on the slats was greatest in birds with the worst (as opposed to better) feather scores of the head, back and tail regions. 4. Birds that spent long periods on the slats were lighter than other birds at both 39 weeks of age and 72 weeks of age and had greater back, head and tail feather damage, consistent with these birds being victims of pecking. 5. Tagged birds received a social avoidance test outside the perchery at 39 weeks of age, which suggested that birds retreated to the slats in response to pecks rather than just to close proximity to other birds. 6. The failure to find that duration on the slats was related to anatomical indicators of stress (liver, spleen and bursa of Fabricius) suggests that retreating to the slats following pecking attenuates physiological stress responses. 7. We conclude that the provision of areas where birds in a large group can avoid pecking may improve the welfare of a minority of victimised birds.