Foot pad dermatitis in growing turkeys is associated with cytokine and cellular changes indicative of an inflammatory immune response.

Cell and cytokine responses during the development of foot pad dermatitis (FPD) in growing turkeys were studied in a model system. The objective was to evaluate the hypothesis that FPD is an allergic response to the environmental materials. Hybrid female turkeys at 28 days of age were exposed to wet litter for 48 h in a randomized block experiment. Expression levels of pro-inflammatory (interleukin (IL)-1 beta, IL-6, and CXCLi2) and signature Th1 (interferon-gamma), Th2 (IL-13) and Treg (IL-10) cytokines were measured in the foot pad tissues using real-time quantitative reverse transcriptase-polymerase chain reaction. Sections of foot pad tissue were stained for CD4+ and CD8+ T lymphocytes, B lymphocytes and macrophages using antibodies that specifically recognize the relevant cell types in the turkey. In the footpads of birds suffering from FPD, there were large fold increases in mRNA expression levels for the pro-inflammatory cytokines IL-1 beta (+635), IL-6 (+65), and CXCLi2 (+1924), and interferon-gamma (+32), whereas there was only a small increase in IL-13 mRNA (+2) and no change in IL-10 mRNA expression levels. CD4+ and CD8+ T lymphocytes were present in the footpads of more than 90% of birds housed on wet litter compared with 25% or less on dry litter. Macrophages were observed in the footpads of approximately 85% of birds housed on wet litter compared with none in birds housed on dry litter. B lymphocytes were not detected in tissue from any of the birds. The data suggest that FPD is associated with a rapidly occurring inflammatory response, rather than a Th2-mediated allergic reaction.

High litter moisture alone is sufficient to cause footpad dermatitis in growing turkeys.

1. Four randomised block experiments were conducted to determine the role of litter moisture, excreta and alternative bedding materials on the development of footpad dermatitis in growing turkeys. 2. Adding water to the litter increased external and histopathological scores independently of the presence of excreta. Fully developed lesions were induced by the application of water to dry litter in 2 to 4 d. 3. Footpad lesions were associated with discomfort during walking in one experiment and body weight was lower in birds on wet compared with dry litter. 4. Footpad lesions had virtually healed 15 d after transfer of the turkeys from wet to dry litter although histopathology assessment showed some residual tissue repair. 5. Long barley straw was associated with high footpad scores on wet and dry treatments. The footpad scores for turkeys on reprocessed cardboard chips were similarly high whereas scores were similar on paper litter and wood shavings whether dry or wet. 6. It was concluded that high litter moisture alone was sufficient to cause footpad dermatitis in young turkeys and that footpad dermatitis should be minimised by the maintenance of dry litter.

High dietary concentrations of biotin did not prevent foot pad dermatitis in growing turkeys and external scores were poor indicators of histopathological lesions.

1. A randomised block experiment was conducted to determine the effects of increasing dietary biotin supplementation (0, 200, 800 and 1600 microg/kg) on macroscopic and histological changes associated with the development of foot pad dermatitis (FPD) in growing turkeys. 2. Each treatment was replicated in 4 pens containing 36 birds at the start of the experiment. The birds were weighed and external foot pads were scored at 2-week intervals from 2 to 14 weeks of age. A blood sample was obtained at the same ages from two birds in each pen and tissue from one foot pad was processed for histological examination. Liver samples were obtained for determination of fat content. 3. Increasing dietary biotin supplementation was associated with higher initial plasma concentrations of biotin but there was no effect on external scores or histopathology of foot pad lesions. FPD increased rapidly from 2 to 6 weeks and remained similar thereafter. There was no effect of dietary biotin on liver fat content. 4. The correlations between external foot pad scores at different ages were all less than 0.4. The correlation between external and histopathological scores was 0.56 and the respective correlations with body weight were 0.52 and 0.65. There were no differences between the body weights of birds with different external scores but high histopathological scores were associated with lower body weights. 5. It was concluded that current recommendations for biotin in wheat-soy rations for growing turkeys are adequate for normal growth and development and that higher supplements of biotin in these experimental conditions did not prevent the occurrence of FPD.

Foot pad dermatitis develops at an early age in commercial turkeys.

1. A field experiment was conducted to identify the macroscopic and histological changes associated with the development of foot pad dermatitis (FPD) in growing turkeys. Two affected and two unaffected turkeys were sampled weekly from 1 to 8 and at 10 and 21 weeks of age. 2. At one week old, birds with external signs of FPD (surface skin discolouration) showed abnormal cellular changes of the foot pad integument. As the flock aged the reactions intensified, with one sample exhibiting a fully developed macroscopic lesion at 3 weeks. 3. Major pathological changes had occurred by 6 weeks and all turkeys with external signs of lesions had fully developed microscopic inflammatory cellular lesions. From 6 weeks of age onwards lesions were increasingly numerous and became more overtly necrotic. 4. Externally normal foot pads showed microscopic evidence of lesions after the turkeys reached 4 weeks. 5. We conclude that FPD lesions become severe over a short period of time and at a very early age.