Different commercial broiler crosses have different susceptibilities to leg weakness

Sequential feeding with variations in energy and protein levels improves gait score in meat-type chickens

Feeding broilers by alternating different diets for 1 or 2 days is known as sequential feeding, and it possibly reduces leg problems since it slows down early growth and may enhance general activity. The present study compared continuous feeding with a standard diet (C: metabolisable energy = 12.55 MJ/kg, crude protein = 190 g/kg) with alternations of a high-energy/low-protein diet (E+P-:+7% ME; -20% CP) and a low-energy/high-protein diet (E-P+: -7% ME,+20% CP) and investigated its effects on growth, behaviour and gait score in 352 male Ross broiler chickens. Sequential feeding was carried out during ten 48-h sequential-feeding cycles from 8 to 28 days of age. Three treatments were compared: complete diet (C) and two alternations of diets varying in protein and energy contents (S1: E+P- followed by E-P+; and S2: E-P+ followed by E+P-). Chickens received the same feed during the starter and finisher periods (0 to 7 and 29 to 38 days of age). Body weight (BW), feed intake, general activity and gait score, bone quality and carcass conformation were measured to evaluate leg condition and general performance. Sequential feeding significantly reduced BW at 28 days of age (S1: -9.1%; S2: -3.7%/C group; P < 0.05) and S1 were lighter than S2. In both sequential groups, time spent standing increased (C: 28%; S1:33%; S2: 35%; P < 0.05) and leg abnormalities decreased (mean gait score: C: 2.61; S1: 2.45; S2: 2.38; P < 0.02). This improvement was not related to changes in bone quality. BW at slaughter was impaired in Group S1 only, and the feed conversion ratio throughout the rearing period was not significantly impaired by sequential feeding. However, abdominal fat was higher in the S2 group. Sequential feeding using diets varying in energy and crude protein can be a useful method of reducing leg problems in broilers since it improves gait score without impairing growth performance when used as early as 8 days of age and up to not less than 8 days before slaughter in order to compensate for reduced growth. This improvement can be explained by reduced early growth and enhanced motor activity. However, it appears that the low-energy diet should be given first in order to avoid a reduction in BW at slaughter.

The effects of growth rate on leg morphology and tibia breaking strength, mineral density, mineral content, and bone ash in broilers

Fast-growing broilers are especially susceptible to bone abnormalities, causing major problems for broiler producers. The cortical bones of fast-growing broilers are highly porous, which may lead to leg deformities. Leg problems were investigated in 6-wk-old Arkansas randombred broilers. Body weight was measured at hatch and at 6 wk. There were 8 different settings of approximately 450 eggs each. Two subpopulations, slow-growing (SG; bottom quarter, n=511) and fast-growing (FG; top quarter, n=545), were created from a randombred population based on their growth rate from hatch until 6 wk of age. At 6 wk of age, the broilers were processed and chilled at 4°C overnight before deboning. Shank (78.27±8.06 g), drum stick (190.92±16.91 g), and thigh weights (233.88±22.66 g) of FG broilers were higher than those of SG broilers (54.39±6.86, 135.39±15.45, and 168.50±21.13 g, respectivly; P<0.001). Tibia weights (15.36±2.28 g) of FG broilers were also greater than those of SG broilers (11.23±1.81 g; P<0.001). Shank length (81.50±4.71 g) and tibia length (104.34±4.45 mm) of FG broilers were longer than those of SG broilers (71.88±4.66 and 95.98±4.85 mm, respectively; P<0.001). Shank diameter (11.59±1.60 mm) and tibia diameter (8.20±0.62 mm) of FG broilers were wider than those of SG broilers (9.45±1.74, 6.82±0.58 mm, respectively; P<0.001). Tibia breaking strength (28.42±6.37 kg) of FG broilers was higher than those of SG broiler tibia (21.81±5.89 kg; P<0.001). Tibia density and bone mineral content (0.13±0.01 g/cm2 and 1.29±0.23 g, respectively) of FG broilers were higher than those of SG broiler tibia (0.11±0.01 g/cm2 and 0.79±0.1 g; P<0.001). Tibia percentage of ash content (39.76±2.81) of FG broilers was lower than that of SG broilers (39.99±2.67; P=0.173). Fast-growing broiler bones were longer, wider, heavier, stronger, more dense, and contained more ash than SG ones. After all parameters were calculated per unit of final BW at 6 wk, tibia density and bone ash percentage of FG broilers were lower than those of SG broilers.

Footpad dermatitis in Dutch broiler flocks: prevalence and factors of influence

In some European countries, footpad dermatitis (FPD) is measured as an indicator of broiler welfare. Prevalence and seasonal variation of FPD was determined within broiler flocks (fast-growing breeds) in the Netherlands. Samples were taken from 386 Dutch flocks at 8 slaughterhouses during a period of one year. Prevalence of footpad dermatitis was related to background information gathered using a food chain certification scheme to identify possible factors of influence. On average, 35.5% of the broilers had no lesions, whereas 26.1% and 38.4% had mild or severe lesions, respectively. Season, age, thinning of flocks, slaughter age, breed, slaughterhouse, and the interaction between thinning and slaughter age significantly affected severity of FPD. Peak flock FPD scores occurred in flocks where 1-d-old chicks were placed in March and December, whereas flocks placed in warm months, between June and August, displayed lower flock FPD scores. Generally, birds sent to slaughter when thinning a flock displayed less severe FPD than birds from completely depopulated flocks. Severity of FPD decreased with age. Because poultry farmer, hatchery, veterinary practice, and feed manufacturer were included in the model as random factors, it was only possible to assess their contribution relative to each other. The broiler farmer had the largest contribution. Also, a large contribution was found for hatchery, perhaps indicating that broiler quality is important. No relationship was observed between FPD and mortality. Across farms, less severe FPD was observed on farms using antibiotics. However, within farms, FPD was more common in flocks where antibiotics had been used compared with flocks that did not require antibiotic treatment. In conclusion, footpad dermatitis was frequently observed in Dutch fast-growing broiler flocks, and many factors had significant effects on severity of FPD, such as breed, thinning of flocks, age at slaughter, slaughter plant, and hatchery.

Genetic parameters of foot-pad dermatitis and body weight in purebred broiler lines in 2 contrasting environments

The aims of this study were to investigate the genetic background of foot-pad dermatitis (FPD) in 4 different broiler lines reared in 2 contrasting environments (pedigree or sib-test) and to evaluate the performance of simultaneous genetic selection for improved FPD and BW. Data were available for 4 generations from 4 broiler lines, bred with varying intensities of selection for growth. The average BW ranged from 1.7 to 2.4 kg at 5 wk of age. In the pedigree environment, the prevalence of FPD ranged from 14 to 37%, with 3 to 9% being severely affected; in the sib-test environment, these values were correspondingly 45 to 79% and 35 to 70%. Both traits showed re-ranking of the 4 lines in terms of phenotype across the 2 environments, indicating the existence of a genotype-by-environment interaction. In both environments, females showed higher prevalences of FPD than males. In line with their higher prevalence, heritabilities of FPD in the sib-test environment ranged from 0.22 to 0.32, compared with 0.18 to 0.24 for FPD in the pedigree environment (all SE ≤0.02). Estimates of the genetic correlation between FPD in the pedigree and in the sib-test environments were high (0.78-0.82), which suggests that selection against FPD in a highly biosecure environment can improve the genetic merit for birds reared under commercial conditions. Estimates of the genetic associations between FPD and BW were small and varied in sign. Predicted responses to selection showed a yearly reduction in average score of -3.4 to -7.5% for FPD in the pedigree environment and -0.5 to -6.6% for FPD in the sib-test environment, while maintaining improvement of BW of 2.6 to 3.2% and 2.6 to 3.8% of the average BW per year, respectively. This research indicates that balanced genetic selection for both BW and FPD in contrasting environments is an effective strategy to reduce the genetic disposition to develop FPD in broilers.

Animal behavior and well-being symposium: Farm animal welfare assurance: science and application

Public and consumer pressure for assurances that farm animals are raised humanely has led to a range of private and public animal welfare standards, and for methods to assess compliance with these standards. The standards usually claim to be science based, but even though researchers have developed measures of animal welfare and have tested the effects of housing and management variables on welfare within controlled laboratory settings, there are challenges in extending this research to develop on-site animal welfare standards. The standards need to be validated against a definition of welfare that has broad support and which is amenable to scientific investigation. Ensuring that such standards acknowledge scientific uncertainty is also challenging, and balanced input from all scientific disciplines dealing with animal welfare is needed. Agencies providing animal welfare audit services need to integrate these scientific standards and legal requirements into successful programs that effectively measure and objectively report compliance. On-farm assessment of animal welfare requires a combination of animal-based measures to assess the actual state of welfare and resource-based measures to identify risk factors. We illustrate this by referring to a method of assessing welfare in broiler flocks. Compliance with animal welfare standards requires buy-in from all stakeholders, and this will be best achieved by a process of inclusion in the development of pragmatic assessment methods and the development of audit programs verifying the conditions and continuous improvement of farm animal welfare.

Footpad dermatitis in poultry

Footpad dermatitis (FPD) is a condition that causes necrotic lesions on the plantar surface of the footpads in growing broilers and turkeys. This condition not only causes downgrades and condemnations of saleable chicken paws, the portion of the leg below the spur, but is also an animal welfare concern in both the United States and in Europe.. Revenue from chicken paws in 2008 alone was worth $280 million. Harvesting large, unblemished paws has become a priority to poultry companies all over the world. Research on this subject has been ongoing since the 1940s and has looked into many different areas including nutrition, environment, and genetics. Early research looked at nutritional deficiencies such as riboflavin and biotin mainly in turkey poults. This early research was most likely looking at a separate form of dermatitis than what is being investigated now. Recent findings have suggested that there is a myriad of interacting factors that lead to FPD. Litter moisture appears to be the most likely culprit in the onset of this condition. Research has also shown a possible genetic link in the susceptibility to development of FPD lesions. Current chicken paw prices have skyrocketed due to a large export market in Asia. To produce unblemished paws for both increased profit and comply with current animal welfare recommendations, further research is needed to understand how the condition develops and what strategies can be used to prevent it.

Effects of different management factors on broiler performance and incidence of tibial dyschondroplasia

(1) This study was to determine the effects of two lighting programmes (continuous--24L:0D or intermittent--12L:3(1L:3D)), two feeding programmes (continuous--ad libitum or meal Jeeding--3 h feed:3 h deprivation x 4 times per d) and two ascorbic acid (AA) supplementations (0 or 150 mg/l in water) on broiler performance and incidence of tibial dyschondroplasia (TD). (2) One-day-old male commercial (Ross PM3) broiler chicks (1600) were used. The chicks were randomly divided into 8 treatment groups (2 x 2 x 2) and their replicates (2) replicates per treatment). (3) Intermittent lighting increased body weight and improved feed conversion. Body weight of broilers was decreased by meal feeding. AA supplementation had no significant effect on the body weight and feed conversion ratio. There was no lighting x feeding x supplemental AA interaction for body weight, feed conversion ratio, mortality rate and carcase weight. (4) Supplemental AA improved the cortical thickness of tibiotarsus and decreased the incidence of TD. (5) It was concluded that the application of intermittent lighting in combination with supplementation of 150 mg/l AA is a useful method to reduce TD in broilers without loss of performance.

Footpad dermatitis in broiler chickens in Japan

The prevalence of footpad dermatitis (FPD) in broiler chickens in Japan was investigated. In the first examination at slaughterhouses, lesions were commonly observed on the footpads of a total of 8,985 broiler chickens from 45 flocks on 36 farms. In 3 flocks, all the birds examined had lesions. In the other 42 flocks, the incidence of FPD ranged from 31.9% (81/254) to 99.5% (1/222). The footpad lesions were classified into 4 categories according to the severity of dermatitis as follows; score 0, 1,181 birds (13.1%); score 1, 2,992 birds (33.3%); score 2, 3,000 birds (33.4%); and score 3, 1,812 birds (20.2%). The mean scores of the flocks varied widely from 0.31 to 2.69. Males had higher mean scores than females. No significant differences were found between the mean scores of birds reared in windowless houses and those in open-sided houses. On 4 farms, the investigation was carried out in different seasons, and 3 of them showed higher mean scores in winter than in summer. Next, observation of 2,255 birds from 15 flocks on 5 farms during a 4-week rearing period revealed that FPD was already produced at 7 days of age and worsened with age.

Photoperiodic responses of broilers. III. Tibial breaking strength and ash content

1. A total of 7960 Cobb and Ross broiler males were reared on various photoperiods or continuous illumination in two trials to 35 or 40 d. Tibial breaking strength was measured in both, and tibial ash content determined in the first of the two trials. 2. Tibial breaking strength was significantly affected by photoperiod, body weight, testicular weight, and genotype. Although peak bone strength occurred at about 7 h for Ross and at 12 h for Cobb, with reductions in strength for both shorter and longer photoperiods than these peaks, the removal of body weight effects showed that tibial breaking strength was negatively correlated with photoperiod per se. However, after removal of photoperiodic influences, breaking strength was positively correlated with both body weight and testicular weight. 3. Ross birds had greater tibial breaking strengths than Cobb, irrespective of whether the comparisons were made at the same photoperiod, the same body weight, or the same ash content. 4. Ash content increased according to the logarithm of photoperiod, but was unrelated to body weight. Tibial breaking strength increased with ash content. Ash contents were similar for Ross and Cobb birds. 5. Despite the significant differences in breaking strength and ash content, there were no broken bones or signs of leg abnormality in any of the 300 birds sampled. Tibial breaking strength data may therefore be of limited value in assessing the benefits of photoperiod to welfare in modern broilers.

Broiler Response to Open Field Test in Early Ontogeny

The aim of this study was to observe the development of exploratory behaviour in growing broilers, i.e. their reaction to a novel environment (habituation) during the post-incubation period. Twelve males and twelve females of ROSS 308 line were kept from hatching until 42 days of age in separate pens, under identical husbandry conditions. To study their behaviour, we used the open-field test (OFT). Individual 10-min tests were initiated at the age of 3 days, and were repeated at weekly intervals, i.e. a total of 6 tests were carried out. The results were evaluated using analysis of variance (ANOVA) for repeated measures and Tukey post-hoc test. Broilers of both sexes were most active during the first OFT on day 3 after hatching. In male broilers, we found a significant decrease in all exploratory activities between the first and 2nd OFT; duration of their horizontal locomotor activity was reduced from 104 ± 51.86 s to 3.50 ± 3.50 s (p < 0.05), duration of visual orientation decreased from 327.50 ± 55.94 s to 125.00 ± 31.94 s (p < 0.001), and duration of vocalizations decreased from 412.50 ± 63.12 s to 90.00 ± 34.25 s (p < 0.001). In females, a significant decrease was observed betwen the first and 2nd OFT only in duration of horizontal locomotor activity that decreased from 234.25 ± 52.07 s to 14.25 ± 8.36 s (p < 0.001) and between the first and 3rd OFT in duration of vocalization (decreasing from 430.00 ± 66.30 s in 1st OFT to 60.00 ± 23.35 s; p < 0.001). On the other hand, a significant increase in duration of comfort behaviour was noted between the first and second OFT in both sexes (in males from 95.00 ± 40.76 s to 462.50 ± 38.81 s; p < 0.001; in females from 85.00 ± 31.73 s to 437.50 ± 67.74 s; p < 0.001). Changes in defecation numbers were not significant in either sex. Our findings show that the most profound changes in behaviour of broiler chickens occurred between the first and second OFT, that male broilers used visual orientation in the open field arena more than females in the first test, they vocalized less in the second test, and they seem to have habituated to the novel environment earlier than females.

Skin lesions in broiler chickens measured at the slaughterhouse: relationships between lesions and between their prevalence and rearing factors

1. This slaughterhouse-based study was to evaluate correlations between cutaneous lesions which are linked to animal welfare. The relationships between these lesions and various rearing factors were investigated. 2. The percentage of lesions in each flock was determined by observation at the slaughterhouse. Fifty-five flocks slaughtered between May 2005 and May 2006 in 8 slaughterhouses were investigated. 3. Data relating to farm management and housing factors during the rearing period were collected retrospectively from 36 of the 55 flocks scored for lesions. 4. A negative correlation was observed between (i) presence of breast blisters and deep hock burns, (ii) presence of breast blisters and deep footpad dermatitis, and (iii) presence of breast burns and scratches. 5. We proposed an assessment of broiler chicken welfare at the slaughterhouse on the basis of several criteria: (i) footpad dermatitis, hock burns and breast burns, (ii) scratches, and (iii) breast blisters. 6. The presence of contact dermatitis was related to litter quality and several management factors. Only scratches and breast blisters were related to high stocking density. The type of lesion was related to genotype. Genotype A (fast-growing) had fewer breast blisters but deeper footpad lesions than B (slower-growing).

Quantifying genetic (co)variation and effects of genetic selection on tibial bone morphology and quality in 37 lines of broiler, layer and traditional chickens

1. Tibial bone morphology and quality was assessed at 6, 8 and 10 weeks of age in 12 broiler, 12 layer and 13 traditional lines of chickens. 2. High intraclass correlations (0.65-0.96) were estimated for tibial weight, length, width, strength, stiffness, stress radiodensity, plateau angle but not for cortical width and tibial torsion at 6 and 10 weeks of age and for weight, length, width, strength radiodensity and plateau angle at 8 weeks of age. Lower intraclass correlations (0.4-0.8) were estimated within category (broiler, layer and traditional) for weight, length, width at 6, 8 and 10 weeks, and for stiffness, stress and radiodensity at 6 and 10 weeks, and were lower (<0.33) at 8 weeks of age. Intraclass correlations for tibial torsion angles were low (< or =0.4) at all ages. 3. Tibia from layers and traditional lines were similar suggesting that intensive genetic selection for high rates of egg laying has not changed bone size, shape or quality. Tibia from broilers, as expected, were heavier and larger and the differences were greatest at 6 weeks of age suggesting that the broilers were earlier maturing than layers and traditional lines. Broiler tibiae were more radiodense, stronger and stiffer and had lower stress values than bones from layers and traditional lines. Plateau angles were higher in broilers and torsion angles had higher external rotation compared with layers and traditional lines.

Effect of inulin on growth performance, intestinal tract sizes, mineral retention and tibial bone mineralisation in broiler chickens

1. A 5-week feeding trial with 240 one-day-old male broiler chickens was conducted to investigate the responses of performance, intestinal tract measurements, relative apparent retention of minerals (Ca, Mg, Fe, Zn and Cu), and tibial bone measurements and mineral content (ash and Ca) to dietary graded levels of inulin. Treatments consisted of a maize-soybean meal control diet without or with supplemental antibiotic (flavomycin, 40 mg/kg diet) and 4 diets containing inulin at concentrations of 5, 10, 15 and 20 g/kg. 2. Growth performance of birds and morphological measurements of intestinal tract (duodenum, jejunum, ileum and caeca) showed no response to dietary levels of inulin as compared with the control diet and the control diet with flavomycin. 3. Dietary inulin improved the relative apparent retention of Ca, Zn and Cu (up to 18.4, 35.5 and 466%, respectively), did no affect that of Mg and impaired the retention of Fe. Differences among inulin treatments and control with flavomycin were significant only for Mg content. 4. Dietary inulin increased the concentration of ash and Ca in the tibiae. This effect was not reflected in the tibial bone morphology (weight, length and width). In conclusion, the results from the current study suggest that feeding inulin to broiler chickens may have a beneficial effect on bone quality.

Leg disorders in broiler chickens: prevalence, risk factors and prevention

Broiler (meat) chickens have been subjected to intense genetic selection. In the past 50 years, broiler growth rates have increased by over 300% (from 25 g per day to 100 g per day). There is growing societal concern that many broiler chickens have impaired locomotion or are even unable to walk. Here we present the results of a comprehensive survey of commercial flocks which quantifies the risk factors for poor locomotion in broiler chickens. We assessed the walking ability of 51,000 birds, representing 4.8 million birds within 176 flocks. We also obtained information on approximately 150 different management factors associated with each flock. At a mean age of 40 days, over 27.6% of birds in our study showed poor locomotion and 3.3% were almost unable to walk. The high prevalence of poor locomotion occurred despite culling policies designed to remove severely lame birds from flocks. We show that the primary risk factors associated with impaired locomotion and poor leg health are those specifically associated with rate of growth. Factors significantly associated with high gait score included the age of the bird (older birds), visit (second visit to same flock), bird genotype, not feeding whole wheat, a shorter dark period during the day, higher stocking density at the time of assessment, no use of antibiotic, and the use of intact feed pellets. The welfare implications are profound. Worldwide approximately 2×10¹⁰ broilers are reared within similar husbandry systems. We identify a range of management factors that could be altered to reduce leg health problems, but implementation of these changes would be likely to reduce growth rate and production. A debate on the sustainability of current practice in the production of this important food source is required.

Effect of diet with thiram on liver antioxidant capacity and tibial dyschondroplasia in broilers

1. An experiment was conducted to study the effect of thiram on liver antioxidant capacity and incidence of tibial dyschondroplasia in broilers. 2. One hundred and twenty Avian commercial broilers were allotted at random to three treatments: control group, low thiram group (50 mg/kg) and high thiram group (100 mg/kg). 3. Blood samples were collected to determine the activity of AST (aspartate aminotransferase). At the end of the trial, broilers were killed and liver samples were collected to determine the activity of SOD (superoxide dismutase), GSH-Px (glutathione peroxidase) and MDA (malondialdehyde) content, while the right proximal tibiotarsi were dissected in longitudinal section for assessment of tibial dyschondroplasia (TD) incidence and TD score. 4. The results showed that thiram increased the incidence of TD and TD scores, increased serum AST activity and MDA content of liver, and decreased the activity of SOD and GSH-Px in the liver. 5. They suggest that thiram causes TD in broilers by reducing liver antioxidation capability and damaging liver function; this may be one of the mechanisms by which thiram causes TD in broilers.

Influence of dietary nutrient density, feed form, and lighting on growth and meat yield of broiler chickens

The objective of this study was to examine main and interactive effects of nutrient density (ND), feed form (FF; mash, pellet), and lighting program (12L:12D, 20L:4D) on production characteristics and meat yield of broilers raised to 35 d of age. Diets (starter, grower, and finisher) were formulated so that amino acid levels were in proportion to the dietary energy level. Lighting programs were initiated at 4 d of age. Body weight was not affected by ND when diets were fed in a pellet form but decreased in a linear manner with lower ND when fed as a mash. Final BW of birds fed mash were less than those of birds fed pellet diets. Feed to gain ratio decreased with increasing ND but was not affected by FF. Feed intake decreased with increasing ND and was lower for birds fed mash. The effect of ND on feed intake was less when birds were fed mash in contrast to pellet diets (P(ND x F) < 0.0001). Dietary ND had no effect on mortality, but feeding mash decreased mortality (3.8%) compared with feeding pelleted feed (5.6%). Lighting programs affected production characteristics independently of ND and FF. Use of 12L:12D reduced BW, feed to gain ratio, feed intake, and mortality compared with 20L:4D. Similarly, carcass components were not affected by ND when fed in pellet form but decreased with lower ND when fed as a mash. Overall, carcass yields were reduced when broilers were fed mash or provided with 12L:12D. Female birds had higher carcass yields and increased proportional breast meat deposition compared with males.

The impact of nutrient density, feed form, and photoperiod on the walking ability and skeletal quality of broiler chickens

The aim of this study was to examine the main and interaction effects of 3 dietary nutrient densities (low-, medium-, high-density), 2 feed forms (mash, pellet), and 2 lighting programs (20L:4D, 12L:12D) on the walking ability and skeletal quality of broiler chickens raised to a young age (35 d). Forty-eight birds per treatment (nutrient density x feed form x lighting program subclass) were randomly selected (0 d) for assessment of their gait score (GS) and BW at 11, 18, 25, and 32 d. Samples of birds from various GS classifications were selected at 32 d for radiographs and histology of the femur and tibiotarsus. Bone ash (BA) content was evaluated at 35 d from the right tibiotarsus to assess bone quality. Overall, the mean GS values were low (GS <1). An interaction existed between lighting and sex. Males provided with 20L:4D had a higher GS (0.74) than females (0.45), and this score was greater than for broilers provided with 12L:12D (0.34 and 0.26 for males and females, respectively). Feeding mash reduced the GS (0.29) compared with pellet rations (0.62). The GS increased with age, and by 32 d 2.43% of birds had a GS >/=3. Broilers fed mash had a higher BA content (50.6%) than birds fed pellet diets (49.8%), and the 12L:12D value (50.5%) was greater than for 20L:4D (48.9%). Last, males had a lower BA content (49.8%) than females (50.6%). A positive correlation existed between BW and GS based on sex, where BW at 11, 18, and 25 d affected bird mobility at 32 d (r(2) = 0.39, 0.49, and 0.50 for males; r(2) = 0.34, 0.37, and 0.36 for females, respectively). Radiography and histology were unaffected by GS. This study confirmed that a reduced growth rate improved GS but also demonstrated that overall bird mobility was good and the incidence of skeletal disease was low.

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.

Validation of broiler chicken gait scoring training in Thailand, Brazil and New Zealand

Broiler chickens are the most numerous terrestrial farmed animals on earth. These birds can suffer a range of pathologies which result in lameness, and one technique for assessing the impact of lameness on the individual bird, and on the flock has been gait scoring. This paper describes a study where the results of the same training programme for validated gait scoring are compared for groups of assessors in Thailand, Brazil and New Zealand. A uniform course of training carried out in the classroom, through video assessment and through on-farm training was carried out in the countries named; a total of 95 persons being trained overall. A measure of agreement with the reference scale for the assessors' numerical responses was carried out using a Cohen's Kappa test, and the results indicated significant differences in the ‘origin position’ ie the view taken by the assessors of the impact of lameness on the bird before training had taken place, but a high degree of consistency in the response to training. The study demonstrated that gait scoring can be learned by assessors from different geographical and social backgrounds, and that the ‘rate of learning’ – the improvement in performance in relation to a standard, was similar between the countries studied. The ‘origin’ and ‘final’ position of the assessors pre- and post-training, from the different countries in relation to the reference standard is discussed.

Leg health and performance of broiler chickens reared in different light environments

1. The effects of light source and intensity on leg health and performance of female ROSS 308 broiler chickens were investigated in a 2 x 2 experimental design (8 groups of 275 chicks) of two light sources (Osram biolux and Osram warm-white) and two light intensities (5 and 100 clux, adjusted to fowl-perceived illuminance). 2. At 41 d of age, body weight, gait-score, footpad dermatitis and hock-burn were measured on 50 birds from each light environment. In addition, weekly feed intake and body weight were determined on a group basis and mortality was recorded continuously. 3. The light environment did not affect the severity of the gait-score or hock-burns. The risk of moderate to severe lameness and hock-burns increased with body weight. Birds weighing more than 2400 g had an increased probability of moderate footpad lesions in biolux light. 4. Weight and gait-score, as well as gait-score and hock-burn were positively correlated. Podo-dermatitis was weakly correlated with hock-burn, which contradicts earlier findings. The light environment did not affect feed intake, body weight or mortality. 5. The light sources and intensities employed in this study did not adversely affect production or leg health of broiler chickens reared semi-commercially.

Bone breaking strength and apparent metabolisability of calcium and phosphorus in selected and unselected broiler chicken genotypes

1. The present study examined the bone strength and apparent mineral metabolisability of a selected broiler chicken compared with those of a relatively unselected genotype. 2. Selected (SB) and unselected genotypes (UB) were reared under standard conditions and were fed on either a high quality (HQ) or a low quality (LQ) diet. Tibiotarsi samples were collected at 42 d from SB and compared to tibiotarsi from UB of the same age and the same body mass (BM). 3. Bones were assessed for: bone breaking strength (BBS), morphology (weight and length), and both organic (OM) and inorganic content (ASH). Apparent dry matter digestibility and the coefficient of apparent metabolisability of calcium and phosphorus were determined at the same BM. 4. The BBS of SB (214 +/- 9 N) was greater than that of same-age UB (119 +/- 8 N) but the same as that of same-BM UB (218 +/- 10 N). At the same age, the SB had stronger, heavier bones with more ash and organic matter per unit length of tibiotarsus than UB. At the same BM, the tibiotarsi of the SB were shorter and lighter, with a higher ash and a similar organic content than the bones of the UB. At the same BM, BBS was about 15% lower in both genotypes fed on the LQ compared to the HQ diet. 5. The coefficients of apparent metabolisability of calcium and phosphorus were the same in both genotypes when fed on the HQ diet, but were lower in the SB than in the UB genotype when the birds were given the LQ diet. 6. The tibiotarsi of the selected broilers were stronger, or at least as strong, as those of the unselected broiler genotype, which may be due to similar levels of apparent calcium metabolisability of the selected chickens.

Effects of dietary metabolisable energy, calcium and phosphorus on bone mineralisation, leg weakness and performance of broiler chickens

1. Performance, gait score (GS), tibial dyschondroplasia (TD), and tibia bone mineralisation and breaking strength were determined in 2880 male and female Ross 208 broilers fed on diets with two different concentrations of dietary metabolisable energy (ME) (11.00 or 12.00 MJ/kg) and 4 different concentrations of available phosphorus (aP) adjusted for dietary ME content (4.0, 4.5, 5.0 or 5.5 g/kg aP in starter and 3.5, 4.0, 4.5 or 5.0 g/kg aP in finisher diets containing 12.00 MJ/kg). 2. Tibia ash, calcium (Ca) and phosphorus (P) contents in broilers given diets with low ME (11.00 MJ/kg) were greater than those of broilers given diets with higher ME (12.00 MJ/kg). Tibia ash, Ca and P contents increased curvilinearly with increasing dietary aP content. The dietary aP level had no effect on GS. 3. Dietary concentration of ME or aP had no effect on tibia breaking strength. 4. Walking ability, as measured by GS, was negatively correlated with the body weight (BW) of tested birds at 23 and 35 d of age, but the dietary ME content or aP level had no significant effect on GS at 35 d of age. 5. The results indicated that bone mineral content had no clear correlation with the walking ability of broilers.

Chicken welfare as indicated by lesions on carcases in supermarkets

1. The extent of visible lesions in British broiler carcases was investigated in order to discover the extent of any poor welfare. It is well established that hock burn and some other injuries can occur during housing of broiler chickens, whilst other injuries can occur during handling. 2. Three hundred and eighty-four whole conventionally reared British Farm Standard Grade A chickens were scrutinised in supermarkets to assess the frequency of 15 kinds of lesions. Six lesions were analysed histopathologically and this showed that hock burn would have occurred several days pre-mortem, red alular and wrist bruise were very likely to have occurred pre-mortem, whilst red parson's nose and scratches were likely to have occurred pre-mortem. 3. Many broiler carcases in the supermarkets had dermal lesions: 0.82 had hock burns, 0.45 a red parson's nose, 0.32 a red alular, 0.21 wrist bruises and 0.21 had at least one scratch on a leg. The frequency of the larger hock burns increased with body weight. 'Organic' chickens had half as many hock burns as conventionally reared broilers, perhaps because of differences in litter quality or leg strength. 4. The sample studied indicates that painful lesions which would result in poor welfare are frequent in broilers slaughtered in the UK. The Grade A chickens observed exclude birds with obvious visible defects because these birds would have had the blemishes removed and the carcase would have been portioned. Hence the frequencies of lesions in farmed birds would be higher than those reported here.

Development of the skeleton and feathers of dusky parrots (Pionus fuscus ) in relation to their behaviour

A clutch of five dusky parrots (Pionus fuscus) was observed from hatching to fully grown. They were examined radiographically from 16 to 45 days of age, a few days before the cessation of bone growth, and the development of their feathers and their behaviour were also studied. It was observed that when growing birds were removed from the nest and placed singly on a flat surface they would stand up and walk about until restrained; normally these birds would move very little and lie in an intertwined huddle that supported their relatively weak growing skeletons. At 50 days old they would climb to the nest entrance, retreating if scared. From day 51 the parrots flapped their wings vigorously inside the nest box, and they emerged at 53 days old when nearly all their large feathers had finished growing. These findings may help to explain the high rate of juvenile osteodystrophy in hand-reared parrots; premature exercise could lead to pathological deformity of the long bones, especially the major weight-bearing bone, the tibiotarsus.

Can a Modified Latency-to-Lie Test be Used to Validate Gait-Scoring Results in Commercial Broiler Flocks?

Bodily contact with water is a novel and aversive experience for broiler chickens, and this has been used when designing the Latency to Lie (LTL) test. The original testing procedure, in which the birds are tested in groups, involves a certain settling period, which makes the test time-consuming to carry out on commercial broiler farms. Our modifications of the LTL test for on-farm use mean that a) the birds are tested individually without visual contact with other birds; and b) the water tub is already filled with water when the birds are placed in it. The results from the LTL tests can then be compared with the scores achieved for each individual bird on the commonly used ‘gait scoring’ procedure. At 14 farms participating in a larger survey, we used three birds of each gait score from 0 to 4 (when available) for LTL testing. The time spent standing before making the first attempt to lie down was recorded. The results show a clear negative correlation (r = -0.86, P < 0.001) between time spent standing and gait score. The mean LTL values for the different gait scores were all significantly (P < 0.01) different. There was no significant difference in LTL results between flocks. The method described appears to be well suited for on-farm use. If further developed, it could become a useful tool in monitoring programmes for the ongoing efforts aiming at decreasing the levels of leg weakness in modern broiler production.

Differences in the Expression of Genes in Lame and Normal Broiler Chickens Identified by Subtraction Hybridisation

In the UK, broiler chickens are normally slaughtered at about six weeks of age when they weigh approximately 2.2 kg; this contrasts with the growth of an ‘unimproved’ traditional strain of bird such as a White Sussex, which would weigh about 800 g at the same age. Lameness, characterised by abnormal gait, posture and impaired walking ability, can be prevalent in these rapidly growing birds and has been highlighted as a major welfare concern. It is during the later stages of rearing, when the bird is becoming heavy and may be achieving weight gains of over 50 g per day, that lameness begins to have an economic and welfare impact on the flock and to compromise the behaviour of large numbers of birds. A study was carried out to identify potential differences in the expression of genes between groups of lame and normal broiler chickens using subtraction hybridisation. The first group comprised lame birds with measurable gait abnormalities, and the second group comprised sound (not lame) birds. Both populations came from within the same flock. After extraction of mRNA and creation of cDNA, subtractive hybridisation was performed to eliminate genetic sequences common to both populations. The resultant DNA was separated and presented for sequence data analysis and comparison with a large sequence database. Some examples of the subtracted sequences detected are given, and the potential significance of these sequence differences at the individual and group level is discussed.

A Comparison Between Leg Problems in Danish and Swedish Broiler Production

In Denmark and Sweden, surveys were undertaken to estimate the prevalence of leg problems in conventional broiler production. The Danish survey included 28 Ross 208 flocks, and the Swedish survey included 15 Ross 208 and 16 Cobb flocks. Leg problems included reduced walking ability (gait), tibial dyschondroplasia (TD), varus/valgus deformations (VV) and foot-pad dermatitis (FPD). Danish Ross chicks showed a significantly higher prevalence of gait score > 0, gait score > 2 and TD, but a lower prevalence of VV, than Swedish Ross chicks. Cobb chicks showed a significantly higher prevalence of gait score > 0, gait score > 2 and TD than Swedish Ross chicks, a significantly higher prevalence of VV than Danish Ross chicks, and a significantly lower prevalence of FPD than both Danish and Swedish Ross chicks. The two genotypes of Swedish chicks showed similar relationships between body weight and probability of gait score > 0, TD and VV, indicating that the difference in prevalence of these leg problems may be due to the difference in mean body weight at slaughter age. At body weights below 2300 g, Danish chicks showed a higher probability of gait score > 2 than Swedish chicks. Furthermore, at body weights below 1900 g, Danish chicks had a higher probability of TD than Swedish chicks, whereas at body weights above 2200 g they had a lower probability of TD. This indicates that the difference in prevalence of TD between Danish and Swedish chicks was due to differences in mean body weight at slaughter age as well as housing conditions. Therefore, further studies on the risk factors in relation to management and housing conditions are required.

Growth curves for body weight and major component parts, feed consumption, and mortality of male broiler chickens raised to maturity

Body weight; yield of the major carcass component parts of breast, leg, thigh, drumstick, breast meat, thigh meat, and drumstick meat; feed consumption; feed conversion; and mortality of male broiler chickens from two commercial strains were measured from hatching to 154 d of age. As no differences were observed between the two strains, for any of the traits measured, the statistical analysis was made using pooled data. Growth curves for BW, breast weight, and leg weight were calculated. The Richards function was chosen to fit the data. The type of the curves predicted was typically sigmoid. Asymptotic weights for BW, breast weight, and leg weight were estimated at 6,870.2, 1,744.2, and 851.5 g, respectively. Age at point of inflection, at which maximum growth rate is attained, was predicted at 44.4, 47, and 49.1 d, respectively. The percentage of breast and breast meat increased with age, whereas percentages of leg, thigh, and drumstick remained roughly constant. Weekly feed conversion was determined, and polynomial functions were applied to relate feed consumption and feed conversion to the age of the birds. Cumulative mortality increased with age, especially beyond 70 d of age, rising to 50% by the end of the experiment. Mortality was related to high incidence of leg weakness observed in the same period. The results of the current study provide information on the growth potential of contemporary, genetically improved broiler chickens by means of a mathematical model.

Reliability and validity of a modified gait scoring system and its use in assessing tibial dyschondroplasia in broilers

1. The gait scoring system for broilers developed by Kestin et al. (Veterinary Record, 131: 190-194, 1992) has been widely used to evaluate leg problems. The many factors and measures associated with this scale have empirically established its external (biological) validity. However, published test-retest (within-observer) reliabilities are poor, and inter-observer reliabilities are unknown. We evaluated several modifications to this scale aimed at improving its objectivity and reliability. 2. Eighteen naïve observers scored a standardised video of birds exhibiting varying degrees of lameness, either using Kestin et al.'s system, or our modified system. 3. Test-retest reliability (0.906) for Kestin et al.'s system was higher than previously reported. Inter-rater reliability was also good (0.892). The modified system offered significantly better test-retest (0.948) and inter-rater reliabilities (0.943), without incurring costs in terms of time taken or difficulty of use. The systems were consistent, assigning individual birds the same score on average. 4. It is concluded that the modified system offers the advantages of reduced error within and between studies. 5. In a second experiment, we used our modified scoring system to examine the relationship between tibial dyschondroplasia (TD) and gait score in 267 selected broilers. 6. Neither the presence nor severity of TD affected gait score, suggesting that, at least in this strain of broilers, other leg problems like slipped tendons or torsional deformities had more influence on gait impairment than did TD.

Dehydration and Lameness in a Broiler Flock

A case study is described in which a high incidence of lameness in broiler chickens (Gallus gallus domesticus) is associated with rearing to 84 days of age; broilers are normally slaughtered at less than 50 days of age. A sample of 185 birds was scored for walking ability, and 24 birds from this group were assessed for dehydration by measuring plasma osmolality. The proportion of the group having gait abnormalities was compared with that recorded during a recent survey of Danish flocks and was found to be higher. A relationship is established between the degree of gait impairment and the level of dehydration. The degree of dehydration is related to the findings for plasma osmolality from previous research, and the results indicate that some of the birds in this case may have been deprived of access to water for periods in excess of 60 hours.

Effects of strain, maternal age and sex on morphological characteristics and composition of tibial bone in broilers

1. This study was to determine the effects of strain, age of the maternal flock and sex on morphological characteristics and composition of tibial bone of broilers from hatch to 48 d of age. 2. A total of 600 chicks was obtained from 2 strains of broiler breeder flocks (150/chicks/strain/maternal age). Maternal flock age was classified as young (32 to 35 weeks of age) or old (56 to 58 weeks of age). Birds were reared under standard feeding and lighting regimes. 3. On day 1, 16, 32 and 48, twelve birds were selected at random from each maternal group, strain and sex and killed. The wet bone weight and volume were measured. Morphological characteristics of tibia were determined using radiography. Bone breaking strength was tested. Tibia dry matter, ash content, mineral density and collagen level were determined. 4. A quadratic increase occurred with increase in age of broilers for all variables, except proximal width, medial cortex thickness and distal condyle width which increased in a linear manner. 5. Maternal age had a significant effect only on the variably measured at the time of hatch. On day of hatch bone weight, ash content and bone volume were affected by maternal age, but the extent of this also depended on the strain. 6. The differences observed between strains for bone anatomy and bone mineralisation during the rapid growth period of 16 d were not significant at later ages, with the exception of bone volume. Differences between sexes were evident from 16 to 49 d of age with females having lower values.

Relationships in broiler chickens between lameness, liveweight, growth rate and age

Thirteen genotypes of poultry were selected to represent a wide range of growth profiles and were fed either a non-limiting or Label Rouge diet. The birds' degree of lameness and liveweight were measured after 54 and 81 days. The birds reared on the Label Rouge diets were less lame than birds of the same genotype reared on the non-limiting diet. More traditional and slower growing genotypes tended to be less lame than the modern genotypes reared on the same feeding regimen. All the birds, irrespective of their genotype or diet, were less lame after 54 days than after 81 days. However, when liveweight was included in the analysis as a covariable, many of the differences disappeared. Only age at assessment significantly affected the walking ability of the birds, with the birds being approximately 0.6 units of gait score worse at 54 days of age than at 81 days. The regression coefficient between gait score and liveweight was 1.262 at 54 days and 1.128 at 84 days. The results indicated that liveweight was an important determinant of lameness in the diverse range of genotypes examined, that growth rate was also an important determinant of lameness and that younger birds may be more sensitive to differences in liveweight than older birds.

A note on the effects of perches and litter substrate on leg weakness in broiler chickens

Two trials were conducted to investigate the effect of availability of perches on indices of leg weakness in broiler chickens. A third trial investigated the effect of litter substrate on similar indices of leg weakness in broiler chickens. Leg weakness traits examined were walking ability and tibial dyschondroplasia, tibial curvature, foot burn, and hock burn. Body weight was also measured in all trials. The presence of perches in the rearing pens had no effect on any of the indices of leg weakness examined in either trial. There were no consistent effects of perches on BW. Litter substrate significantly affected some indices of leg weakness; birds reared on wheat straw had poorer walking ability and more foot burn than birds reared on wood shavings, and birds reared on hemp waste were intermediate between them. There was no effect of litter substrate on tibial dyschondroplasia or tibial curvature. Turning the straw litter regularly and adding fresh supplies when necessary did not significantly improve indices of leg weakness. It was concluded that wood shavings provide a better litter substrate than straw, but that perches have no beneficial effect on reducing leg weakness in broilers.

Effects of age and stocking density on leg weakness in broiler chickens

The effects of stocking density (STD) on leg weakness in broiler chickens was assessed in two trials. The interaction between age and STD on leg weakness was further evaluated in one trial. In Trial 1, walking ability was assessed at 28, 42, and 49 d of age. Birds were stocked at 833, 625, or 435 cm2 per bird. In Trial 2, birds were stocked at 625 or 455 cm2 per bird and assessed for tibial dyschondroplasia (TD) by radiographic examination at 28 d and walking ability at 35 d. Foot pad burn, hock burn, and angulation of the hock joint were also assessed at slaughter on Day 42. Body weight was measured during both trials. At 4 wk of age, leg weakness was a relatively minor problem; few severely lame birds had a gait score (GS) of 4 or 5 at any density. However, 2 wk later, the birds had substantially poorer walking ability. Further deterioration had occurred by 7 wk of age. At all ages, males exhibited greater leg weakness than did females, and the proportion of severely lame birds increased with age of assessment. The effect of STD was consistent across both trials; higher STD were associated with poorer walking ability and reduced live weights. In Trial 2, higher STD resulted in more foot and hock burns. Females were more sensitive to STD than were males However, there was no effect of STD on the prevalence of TD or angulation of the hock joint. The effect of high STD on walking ability was apparent even at 4 wk of age. Adjusting the observations for differences in BW did not alter the findings. It was concluded that the lower STD substantially reduced the prevalence of leg weakness.