Influence of stocking density on the performance, carcass characteristics and selected welfare indicators of broiler chickens

AIM: To compare the effects of four stocking densities (5, 10, 15 or 20 birds per m2) on the performance, carcass characteristics and selected welfare indicators of broiler chickens. METHODS: A total of 756 day-old male broiler chicks were assigned as six replicates of 13, 25, 38 and 50 birds per pen, to stocking densities of 2,000, 1,000, 667 and 500 cm2 floor space per bird, respectively. The birds were housed in floor pens in an environmentally controlled room. Normal commercial diets were fed ad libitum and fresh water was freely available throughout the 5-week study period. Liveweights of birds and feed intake were recorded at weekly intervals. Data on carcass parameters and welfare indicators (moisture, gait scores, feather scores, breast and hip lesions, and foot pad and hock burns) were obtained on Day 35. Adrenal glands were removed at slaughter, weighed and examined histologically to determine the total proportion of cortical and medullary tissues. RESULTS: During the study, the birds at the lowest density grew faster (p<0.001-0.01) and consumed more (p<0.001- 0.01) feed than those at the other three stocking densities. The liveweight gains and feed intake of birds reared at densities of 10, 15 and 20 birds per m2 were similar (p=0.11-0.83 and p=0.17-0.57, respectively). Stocking density had no influence on the feed/weight gain, mortality or carcass characteristics. No breast or hip lesions were observed in carcasses from any of the groups. The weight and structure of the adrenal glands were similar across all groups although the staining of medullary tissue of birds was most intense in the highest stocking density group. As stocking density increased, so did moisture and gait score, hock and foot pad burn scores, and the feather score was adversely affected. CONCLUSIONS: The data showed that the relationship between stocking density and productivity traits was not linear in nature, in accordance with other studies. Under the conditions of the current study, the performance, mortality and carcass characteristics of broilers grown at densities of 10, 15 and 20 birds per m2 were similar. There were some welfare implications at high population densities as indicated by adverse effects on litter quality, gait scores and the incidence of hock and foot pad burns.     

Influence of claw clipping, stocking density and feeding space on the incidence of scabby hips in broilers

1. The aetiology of scabby hips was studied in broilers by scratching the skin with chicken claws, clipping the birds' claws and varying the effects of stocking density and food trough allocation. 2. Gentle scratching twice a week resulted in skin lesions that could not be distinguished from clinical scabby hips at slaughter. Interaction between birds appeared to be a prerequisite for the skin condition to develop. 3. Clipping of the claws at day 25 could almost completely prevent scabby hips at day 45 when the birds were slaughtered. 4. No positive correlation was found between feather condition and the severity of scabby hips at slaughter at day 45. 5. Decrease in stocking density and an increase in feeding space resulted in a reduction of skin lesions at day 25 and resultant scabby hips after slaughter.     

The effect of varying stocking density on the development and subsequent laying performance of floor‐reared pullets

Light‐weight, hybrid pullets were reared on litter at 0.070, 0.093, 0.139 and 0.186 m² of floor area per bird. Flock size was constant at 400 birds per pen and other related factors of management were standardised. Results showed that the different densities of stocking had no commercially important effect on growth rate, food consumption or viability, but feathering was poorer in the more densely populated groups.

At 18 weeks of age, some of the birds from each treatment were transferred to battery cages and others to deep‐litter laying quarters and records of their performance in terms of egg production and quality, food consumption, mortality and body weight gain were taken over a period of one year. The use of high stocking densities during the preceding rearing stage caused no impairment of the performance of layers kept in batteries, but was possibly responsible for a small decline in productivity of layers housed on deep litter.     

Survey of the stocking densities at which sheep are transported commercially in the United Kingdom

A total of 6578 sheep carried in 74 vehicles to one slaughter plant were monitored, and stocking densities, in terms of m2 floor area available per 100 kg liveweight, were estimated from the dimensions of the vehicle pens and estimates of liveweight based on chest girth measurements. The observed stocking densities ranged from 0.29 to 2.00 m2/100 kg liveweight, and the average density was 0.65 m2/100 kg. One per cent of the sheep were carried at estimated stocking densities of less than 0.3 m2/100 kg, 37 per cent at densities between 0.3 and 0.6 m2/100 kg and 57 per cent at densities between 0.6 and 0.9 m2/100 kg. Over 30 per cent of the animals in the survey were transported at densities higher than the working recommendations made by the Farm Animal Welfare Council.     

Performance and welfare of broilers as affected by stocking density and zinc bacitracin supplementation

The influence of stocking density (16, 20 and 24 birds/m²) and zinc bacitracin (0 or 100 mg/kg) on the performance, carcass characteristics and some indirect welfare indicators of broilers were examined in a 35‐day trial. The weight gain, feed intake, liveability and carcass characteristics of broilers grown at densities of 16, 20 and 24 birds per m² were similar (P > 0.05). Over the whole trial period, however, feed per gain of birds at the highest density (24 birds/m²) was higher (P < 0.05) than those at the other two densities. Litter quality was poorer at high population densities, but there were no welfare implications as indicated by the lack of effect of density on gait scores and the incidence of hock and fat pad burns. Inclusion of zinc bacitracin improved weight gains and feed intake of broilers over the 35‐day trial period at all three stocking densities tested. Zinc bacitracin supplementation had no influence on the feed per gain of birds reared at densities of 16 and 20 birds/m², but improvements were observed at a density of 24 birds/m². The relative weights of lymphoid organs (spleen and bursa) were lowered (P < 0.05) with increasing density, suggesting a greater degree of stress on the birds. Zinc bacitracin supplementation had no influence on bursa weights of birds reared at densities of 16 and 20 birds/m², but increased the bursa weights of birds reared at a density of 24 birds/m². Overall, these data indicate that, with the removal of in‐feed antibiotics in the future, care should be taken when considering population densities of greater than 20 birds/m².     

Broiler performance under high stocking densities

1. In two consecutive experiments a total of 4,780 broilers were reared at high stocking densities. 2. In experiment 1, the birds were housed at 10, 20, 30, 40 or 50/m2 till 6 weeks. In experiment 2 densities of 20, 40 and 50/m2 were compared; the two higher densities were reduced to 30/m2 at either 3 or 5 weeks of age. 3. In the first experiment 6-week body weight was a curvilinear function of stocking density. Average food intake over the whole experimental period declined linearly with densities above 20/m2. 4. A slight but significant improvement in the efficiency of food utilisation was recorded from birds at high densities in the first experiment only. 5. Reducing the stocking density from 40 or 50/m2 to 30/m2 at 3 weeks increased food consumption and body weight gain and led to a recovery in their body weight by 6 weeks. 6. No significant differences were observed in mortality as a result of high stocking densities in either experiment. 7. Profit margin per m2 increased almost linearly in experiment 1, by about 65 p for every bird/m2 increase in stocking density. 8. The implications for poultry welfare are briefly discussed.     

Assessment of the behaviour and welfare of laying hens on free-range units

The aims of this study were twofold: to develop and test an animal-based protocol for the assessment of the physical and emotional elements of the welfare of laying hens on free-range units and to investigate the effects of different approaches to housing and management on the welfare of the birds. The protocol was tested on 25 free-range units for laying hens, each of which was visited on four occasions by one of five trained observers; further information about husbandry, health and productivity was gathered from interviews with the farmers. Measures of the birds' attitude included arousal, noise, flight distance and response to a novel object, measures of their activity included feather pecking, aggression and use of range, and measures of their physical welfare included mortality, body condition and egg quality. Increased arousal was associated with increased flight distance, greater reluctance to approach a novel object and higher levels of feather pecking and feather loss, but the correlation between pecking and feather loss was low. The birds maintained body condition throughout the period of lay. Neither body condition, feather pecking nor feather loss was affected by the extent of beak trimming. Estimated losses (deaths and culls) ranged from 1.8 to 21.4 per cent (median 6.95 per cent). Few birds showed signs of ill health, limb lesions or red mite infestation. No feature of building design had a significant effect on mortality, but there were consistent differences in the birds' attitude, behaviour and performance attributable to the type of floor and the presence or absence of perches, which suggested that the welfare of the hens was inferior when they were housed on plastic floors with no perches.     

Spatio-temporal factors influencing the occurrence of Syngamus trachea within release pens in the South West of England

Syngamus trachea is a pathogenic tracheal nematode that causes syngamiasis in wild and game birds, especially when birds are managed at high densities. Despite its pathogenic nature, very little is known about its epidemiology and relationship with ambient temperature and humidity. The spatial and temporal modelling of disease was undertaken on two pheasant estates within the South West of England from April 2014 to August 2014. Significant differences between the mean numbers of eggs per gram of soil were identified between pens at both site 1 and site 2 but did not differ significantly between sites. Egg abundance was significantly associated with soil moisture content, with greater egg survival between years in pens with higher average volumetric soil moisture content. Previous years stocking density and pen age were also associated with greater egg survival between years with more eggs being recovered in pens with greater stocking densities, and pens that had been sited longer. The greatest model to explain the variation in the numbers of eggs per gram of soil per pen was a combination of soil moisture content, stocking density and pen age.Larval recovery differed significantly between sites. Larval abundance was significantly and positively associated with temperature and relative humidity at site 1. Similarly, temperature and humidity were also positively and significantly associated with larval abundance at site 2. Rainfall did not influence larval recovery at either site 1 or site 2. The model with the greatest ability to explain larval abundance at both sites, was a combination of temperature, humidity and rainfall. Infection status (positive faecal egg counts) was significantly and positively associated with larval abundance at both sites, but rainfall was only positively associated at site 1. Temperature and humidity were positively associated with infection status at site 2, but not at site 1. The present study highlights the influence of climatic variables on both egg survival and larval abundance, and could therefore be used to develop more targeted treatment strategies around periods of higher disease risk. The frequent use of release pens is a clear factor in the epidemiology of syngamiasis, and it is recommended that pens be rested and/or rotated in order to reduce infection pressure in subsequent flocks.     

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.     

Incidence of histomonosis in turkeys in France since the bans of dimetridazole and nifursol

Between April 2003 and March 2005, 113 outbreaks of histomonosis were recorded in standard turkey farms in France, and 15 cases were recorded in turkey breeding centres. Most of the cases were in north-west France, the principal farming area for turkeys. The majority of the cases occurred during the hottest months, from April to September. Large numbers of cases occurred among birds from four to eight weeks of age, but there were some cases in three-week-old birds and some in birds up to 17 weeks of age. In most of the standard turkey flocks the mortality was less than 10 per cent, but it was above 30 per cent in nearly 20 per cent of the outbreaks. In the breeding flocks, the average mortality was 60.2 per cent. The size of the flocks, the sex of the birds and the age at which the first clinical signs appeared did not seem to influence the mortality.     

Effect of DDT, intensive use of the floor surface and post-incubation stress on the development of immune response in chickens]

We studied the long-term effect of civilization factors, DDT, high stocking rates, and post-incubation stress on the antibody response to the administration of Newcastle disease vaccine. The chickens were divided into three groups after hatching. The first group was fed a mixture with an addition of commercial DDT (100 mg per 1 kg of feed). The second group was given the same feed and, in addition, was kept at a high stocking rate. Half the experimental chickens of each group were tied in the third post-natal week, to subject the birds to another stress. Those in the control group remained intact. The results indicate that DDT administered with food increased the immunity response to the antigen stimulus. The additive stress from high stock densities reduced the immunity response, and decreased the response raised by DDT administration to the level of the control. The post-incubation stress was found to modify the long-term effect of DDT and high stocking rate upon the immunity response of the chickens.     

Pop hole passages and welfare in furnished cages for laying hens

1. This study included two designs of furnished cages for 16 hens; H-cages divided into two apartments by a partition with pop holes in the middle of the cage, and fully open O-cages, without a partition. The hypothesis was that in this rather large group of birds the pop hole partition would benefit the birds by allowing them to avoid or escape from potential cannibals, feather-peckers or aggressive hens. All cages had two nests, two perches and one litter box. 2. A total of 10 cages (5 H and 5 O) were stocked with Lohmann Selected Leghorn (LSL) and 8 cages (4 H and 4 O) with Hy-Line W36. No birds were beak-trimmed. 3. Heterophil/lymphocyte (H/L) ratios, duration of tonic immobility (TI) and exterior appearance (scoring of plumage condition and wounds at comb or around cloaca) were used as indicators of well-being. Total mortality and deaths due to cannibalism were also recorded. 4. Visits to nests and passages through partition pop holes were studied in samples of 35 and 21 birds, respectively, using a technique based on passive integrated transponder (PIT) tags. 5. Cage design (H- vs O-cage) had no effect on the welfare traits chosen. 6. Hy-Line birds showed higher H/L ratios, longer duration of TI and better plumage condition than LSL birds. These differences are discussed in terms of stress thresholds and copying strategies. 7. On days when a hen made visits to nests, the visiting frequency was 1.4 and the total time in the nest was 41 min on average. Hens made use of the pop hole passages between 1 and 8 times per hen and day. 8. Overall low levels of aggression, lack of injuries or deaths due to cannibalism, and plumage condition indicating moderate feather pecking, together imply a low need to escape. The pop holes were used frequently and birds distributed well between compartments showing that the system worked well. However, at this group size there was no evidence in the measured traits that H-cages provided a better housing environment.     

Preliminary investigations of ultraviolet-induced markings on domestic turkey chicks and a possible role in injurious pecking

Several gallinaceous species including domestic turkeys have the capacity for ultraviolet (UV) vision. This might function in signalling between birds, for example in individual recognition, which would suggest the presence of plumage markings visible under UV radiation. Between 1 and 22 d of age, the plumage of 17 male turkey poults (BIG6) was examined. When viewed under a conventional fluorescent white luminaire (which emits minimal UV) the birds were a uniform yellow or white according to the stage of feather emergence. However, when viewed under a lamp emitting radiation with peaks in the UV spectrum, distinct fluorescent and non-fluorescent patches were observable on several parts of the body including the wings, tail, shoulders, thighs, neck, breast and dorsal surface. This paper describes the changes in incidence, size, location and qualitative aspects of these UV-visible markings. The age at which UV-visible markings were first observed on the wings and tail corresponded closely with the age at which injuries to these sites were first caused by pecking, as reported previously. It is suggested that the 'unnatural' appearance of these markings under conventional lighting, which emits minimal UV radiation, might attract or protract injurious pecking from conspecifics.     

Efficacy of danofloxacin in the therapy of experimental mycoplasmosis in chicks.

Specific pathogen free day-old chicks were inoculated with a virulent strain of Mycoplasma gallisepticum. Birds received either danofloxacin (50 ppm), tylosin (500 ppm) or no medication in the drinking water from 24 hours after infection for three days. The effects of medication on mortality, weight gain, serology, lesions and reisolation of M gallisepticum 21 days following infection were studied. Treatment with danofloxacin and tylosin significantly decreased mortality and increased weight gain compared with infected unmedicated birds. Twenty-one days after infection, M gallisepticum was isolated from 96 per cent of unmedicated birds compared with only 6 per cent of danofloxacin-treated and 40 per cent of tylosin-treated birds, and the percentage showing positive serological tests was reduced from 100 per cent of unmedicated birds to 0 per cent of danofloxacin-treated and 29 per cent of tylosin-treated birds. In both cases, the proportion of positive birds from the danofloxacin-treated group was significantly lower than that from the tylosin-treated group. The occurrence of air sac lesions was also significantly lower in danofloxacin-treated than in tylosin-treated birds.     

Duration of wing flapping in chickens shackled before slaughter

Shackling can induce wing flapping in chickens. In this survey of 30 chicken processing plants the proportion of birds flapping their wings had usually subsided to less than 0.5 per cent after the birds had been conveyed 2 m away from the shackling area. Thereafter, there were many causes of wing flapping, of which the following were thought to be important; tight fitting shackles on the birds' shanks, electric shocks at the water bath stunner before stunning, sudden bright sunlight, bends in the line, temporary loss of visual contact between neighbouring birds, and unevenness in the line which jolted the birds. If it is decided that legislation is required to prescribe a minimum 'hang-on' period before stunning it is suggested that birds should not be put through the stunner less than 12 seconds after shackling because after this time 99.7 per cent of the birds had stopped flapping.     

The effect of environmental factors on activity,selected behaviour patterns and “fear” of fowls in cages and pens

The causes of feather pecking are closely linked with the nature of the environment in which the bird is kept. The object of this study was to assess the influences of group size, stocking rate and illumination intensity on general activity, preening, head shaking and “ fear ” responses and to relate these activities to feather pecking. In caged birds activity was increased by brighter light, by more space per bird and by more birds in a group; more preening was seen in birds housed at a lower density and no treatment had an effect on head shaking. “ Fear ” responses were greater in dim light and particularly when group size was large. Birds in pens appeared to lack completely “ fear ” responses to the stimulus used. In pens only stocking rate was varied; it had the same effect on activity as in cages. At higher stocking rates birds in pens showed more head shaking. The relationships between feather pecking, “ fear ” responses and general activity are discussed.     

Pathogenesis of marble spleen disease in bursectomized and non-bursectomized ring-necked pheasants following oral inoculation with cell-culture-propagated virus.

Seventy-two 13-week-old ring-necked pheasants were inoculated orally with 5.0 x 10(2) tissue-culture infective dose (TCID) of cell-culture-propagated marble spleen disease virus. Inoculated birds exhibited neither mortality nor clinical disease. Gross and histologic lesions were typical of marble spleen disease. The mean splenic weight was significantly (P less than 0.02) higher in inoculated birds than in controls between 6 and 10 days postinoculation (PI). The histologic splenic lesions, which consisted of reticuloendothelial cell hyperplasia, intranuclear inclusions within reticuloendothelial cells, and lymphoid depletion, were most prominent between 6 and 10 days PI. In a second experiment, 1-day-old pheasants were chemically bursectomized by dosing birds with 1.2 mg cyclophosphamide on 3 consecutive days. At 7 weeks of age, 54 bursectomized birds were inoculated orally with 5.0 x 10(2) TCID of marble spleen disease virus. Gross and histologic lesions were detected in one of the inoculated pheasants, but the mean splenic weight was not significantly different from control birds at any time PI. These results are evidence of the role of the bursa of Fabricius in the pathogenesis of marble spleen disease.     

Influence of stocking density on behavioural, health and productivity traits of turkeys in large flocks.

1. The effect of stocking density on welfare traits of turkeys was studied in 2 experiments. In each experiment 2,633 sexed BUT turkey poults were assigned to 3 rooms, 135 m2 with 1 treatment per room. Because of the large flock size (675,878 and 1080 birds in T1, T2 and T3 respectively) treatments were not replicated 2. Floor space allowances varied according to treatment; for the males: 24 dm2, 18.5 dm2 and 15 dm2 until week 12 and 40 dm2, 31 dm2 and 25 dm2 from week 12; for the females: 16 dm2, 12.3 dm2 and 10 dm2. 2. The scan sampling method in experiment 1 and the focal sampling method in experiment 2 were used to record behaviour at week 6, 9, 12 (males and females), and 16 (males). Birds' ethogram was divided into 7 mutually exclusive behaviours: standing/walking, resting, feeding, drinking, pecking at the environment, pecking at another bird, and preening. Position changes in the pen and the frequency of disturbances of resting birds by other birds were recorded in experiment 2. 3. Gait was assessed at week 12 (females) and week 16 (males). Prevalence of lesions, breast (males), hip and foot (males and females), were recorded at slaughter. Birds were weighed at week 12 (males and females) and week 16 (males). 4. Stocking density had little influence on behaviour except on the frequency of disturbances of resting birds by other birds, which tended to be more frequent at the highest density. 5. Gait deteriorated as stocking density increased. Hip and foot lesions were more frequent at the highest density. Bodyweight decreased significantly with decreasing floor space. 6. The results suggest that turkey welfare was poorer at the highest density than at the 2 lower stocking densities.     

Effects of stocking density on growth performance,meat quality and tibia development of Pekin ducks

This study was performed to investigate the effects of stocking density on performance, meat quality and tibia development in Pekin ducks reared on a plastic wire floor. A total of 372 healthy, 21‐day‐old, male ducks with similar body weight (BW) were randomly allotted to stocking densities of five (low), eight (medium) and 11 (high) birds/m². Each group had six replicates. Results showed that compared with the low density group, medium and high stocking density caused a decrease in final BW at 42 days old, and in average daily gain, European performance index (p < .01) and meat pH at 45 min postmortem (p < .001), and an increase of meat drip loss (p < .01). High stocking density resulted in an increase of feed/gain ratio (p < .001), but a decrease of tibia calcium (p < .01) and phosphorus content (p < .05). Meat color, shear force values, tibia size (weight, length, and width) and breaking strength were not significantly influenced by stocking density. In conclusion, stocking density over eight birds/m² negatively affects growth performance, but meat quality and tibia development are not dramatically influenced. Based on this study, the stocking density of male Pekin ducks should be adjusted between five and eight birds/m².