Wet litter not only induces footpad dermatitis but also reduces overall welfare, technical performance and carcass yields in broiler chickens

Introduction

Footpad dermatitis (FPD), also called footpad lesions or pododermatitis, is a major welfare concern in broiler chickens. Severe FPD is likely to be painful for the birds, and because of its association with litter quality it also reflects other welfare aspects (Haslam et al., 2007).Wet litter is the most important factor causing FPD in broiler chickens (Shepherd et al. 2010). It can be expected that the prevalence of severe FPD is accompanied by other negative effects on welfare and productivity caused by a deteriorated litter quality. Fast growing broiler chickens from three weeks of age onwards spend a considerable amount of time sitting (e.g. Alvino et al., 2009). When sitting, the hocks as well as the chest region are in contact with the litter. It can be expected that increased litter moisture not only increases the risk for FPD, but also for hock burns (hock dermatitis) and dermatitis of the skin on the chest (Allain et al., 2009; Greene et al., 1985; Martland, 1985). This may in turn lead to reduced carcass quality of the broilers and an increased number of downgraded carcasses at the slaughter house. In addition, broilers suffering from pain caused by FPD (Martland, 1985; Martland, 1984) and possibly also from dermatitis on the hocks and breast may be less eager to go to the feeders and drinkers and thus may show less weight gain as broilers having no FPD.

In an experimental setting technical performance, carcass yield and additional welfare indicators of broilers with a high incidence of FPD (induced by increasing litter moisture content) was compared with a control group having low incidences of FPD.

Material and methods

7,200 Day-old Ross 308 broiler chickens (as hatched) were housed in 8 identical floor pens (47.5 m²) bedded with white wood shavings (1 kg/m²) in two identical, climate controlled rooms until slaughter at 37 days of age. Per pen, 900 broilers were housed (19 chicks/m² at placement). The broilers were housed under conditions similar to Dutch commercial farms and received a commercial multi-phase diet. Lights were continuously on at day 1 and 2, and on day 37. From day 3 to 36 an intermittent lighting schedule was applied of 4L:4D:(4*(3L:1D)). Feed and water were supplied ad libitum during the whole experimental period.

The experiment aimed to have two contrasting treatments with respect to FPD: groups of broilers having a very low percentage of FPD (control, n=4 pens) and groups of broilers having a very high percentage of severe FPD (lesion-induction, n=4 pens). FPD was induced by systematically spraying water over the litter starting from day 6 of age and during 5 subsequent days per week until the end of the experiment. In the control groups, the development of FPD was prevented by keeping the litter as dry as possible. This was done by replacing wet spots underneath the drinking lines by fresh litter, adding fresh litter on top and by daily raking the litter underneath the drinking lines from two weeks of age onwards.

Technical performance (body weight, body weight gain, feed intake, water consumption, feed conversion ratio and mortality), slaughter yields (carcass yield and processing yields (wing, leg, fillet)) and rejections, litter quality, external quality (e.g. severity of footpad dermatitis, hock burns, breast cleanliness, breast irritation and thigh scratches) and gait score were measured.

All data were analysed by ANOVA with treatment (percentage of FPD: low and high) as factor and room and row within the room as blocking factors.

Results

As a result of water spraying in the lesion-induction groups and the active litter management (raking, litter adjustment and litter replacement) to prevent the development of FPD in the control groups, litter quality was significantly worse in the lesion-induction groups as compared to the control groups. The increased litter moisture content induced the development of FPD in the birds. At day 36, 99% of the birds in the lesion-induction groups had severe FPD compared with only 2% in the control groups.

The lesion-induction group had a significantly decreased growth, feed intake and water intake and an increased feed efficiency as compared to the control group (Table 1). These differences in performance were observed from day 28 of age. Before 28 day no significant differences in performance were observed. No differences were observed in mortality between the treatments.

Due to the higher growth rate a higher body weight and carcass weight were found for the control group as compared to the lesion-induction group at 37 days of age (Table 2). Compared with the lesion-induction group broilers from the control group had a lower wing percentage. No differences were found in carcass, leg and breast fillet percentage between control and lesion-induced group. There were no differences in percentages of downgraded carcasses, but the percentage of downgraded commercial parts was significantly higher in the lesion-induction group as compared to the control group (Table 2).

The induction of FPD was accompanied by a reduced bird cleanliness, increased incidence of hock burn and breast irritation and a worse locomotion at 36 days of age compared with the control groups. On the other hand, more thigh scratches were found in the control group as compared to the lesion-induction group (Table 3).

An economic calculation was performed based on the technical results of the current experiment. The lesion-induction group had a lower margin of 8.9 €cents per broiler placed than the control group which is a considerable difference. For a broiler farm with 90,000 places this means a difference of €8,500 per flock or € 62,000 per year.

Negative side effects of FPD on production and carcass yield may function as an additional incentive for farmers to reduce the risk for FPD and thus improve welfare in their flocks.

Conclusions

Induction of footpad dermatitis in broiler chickens by experimentally increasing the litter moisture content is accompanied by reduced technical performance, welfare and more rejections of commercial parts at the slaughter house as compared control groups of broilers kept on dry litter without severe footpad dermatitis;
Prevention of footpad lesions in broilers is therefore not only preferred from a welfare point of view but also from an economic point of view. Not only because footpad lesions have an economic value in itself but also because the negative associations with technical performance and downgraded carcass quality.

References

Allain, V., Mirabito, L., Arnould, C., Colas, M., Le Bouquin, S., Lupo, C., Michel, V. (2009). Skin lesions in broiler chickens measured at the slaughterhouse: relationships between lesions and between their prevalence and rearing factors. British Poultry Science 50:407-417.
Alvino, G. M., Archer, G. S., Mench, J. A. (2009). Behavioural time budgets of broiler chickens reared in varying light intensities. Applied Animimal Behaviour Science 118:54-61.
Greene, J. A., McCracken, R. M., Evans, R. T. (1985). A contact dermatitis of broilers – clinical and pathological findings. Avian Pathology 14:23-38.
Haslam, S. M., Knowles, T. G., Brown, S. N., Wilkins, L. J., Kestin, S. C., Warriss, P. D., Nicol, C.J. (2007). Factors affecting the prevalence of foot pad dermatitis, hock burn and breast burn in broiler chicken. British Poultry Science 48:264-275.
Martland, M. F. (1984). Wet litter as a cause of plantar pododermatitis, leading to foot ulcerration and lameness in fattening turkeys. Avian Pathology 1984 13:241-252.
Martland, M. F. (1985). Ulcerative dermatitis in broiler-chickens – the effect of wet litter. Avian Pathology 14:353-364.
Shepherd, E. M., Fairchild, B. D. (2010). Footpad dermatitis in poultry. Poult. Sci. 89:2043-51.

Table 1. Technical performance for the control and lesion-induction treatments over the overall production period (0 -37 days).

Wet litter not only induces footpad dermatitis but also reduces overall welfare, technical performance and carcass yields in broiler chickens - Image 1

Table 2. Carcass yield and percentages of downgrades at day 37 for the control group and the lesion-induction group.

Table 3. Average scores for breast cleanliness, breast irritiation, thigh scratches, hock burn and gait score for the control and lesion-induction group at 36 days of age (breast cleanliness, breast irritation and thigh scratch scores ranging from 0 (none) to 3 (severe); hock burn scores ranging from 0 (none) to 4 (severe); gait scores ranging from 0 (excellent gait) to 5 (unable to walk).