A comparison of the clinical manifestations of feeding whole and hydrolysed chicken to dogs with hypersensitivity to the native protein Rebecca Ricci*, Bruce Hammerberg † , Judy Paps ‡ , Barbara Contiero* and Hilary Jackson ‡ *Department of Animal Science, University of Padova, Viale dell’Universita ` 16, 35020 Legnaro (PD), Italy † Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough Street, Raleigh, NC 27606, USA ‡ Clinical Sciences, College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough Street, Raleigh, NC 27606, USA Correspondence: Hilary Jackson, Veterinary Dermatology Referral Services, 528 Paisley Road West, Glasgow G51 1RN, UK. E-mail: pinerail@mac.com Sources of Funding This study was funded by a grant from Nestle Purina Petcare Company, St. Louis, MO, USA. Conflict of Interest At the time of this study, Hilary Jackson was a member of the Nestle Purina advisory council. Abstract Twenty-six dogs with known adverse food reactions were fed whole chicken for 14 days. From this group, 12 dogs with cutaneous manifestations following exposure to chicken meat were selected and randomly divided into two groups (n = 6). Each group was then fed hydrolysed chicken or hydrolysed soy for 14 days in a blinded crossover design with a 17-day washout period between each diet. Assess- ments of a CADESI (Canine Atopic Dermatitis Extent and Severity Index) score and pruritus were performed throughout the entire study, and com- bined in a global score (GS). Serum was collected weekly for the measurement of chicken- and soy-spe- cific IgG and IgE. Dogs displayed the most severe clinical response when eating whole chicken compared to baseline (P < 0.001). The GS was signifi- cantly reduced in 11 of the 12 dogs when fed hydroly- sed chicken were compared to those fed whole chicken (3.58 ± 2.81 versus 20.38 ± 14.65, P< 0.01). Serum immunoglobulin G and E responses were variable and did not show relationship with specific dietary exposure. Accepted 10 August 2009 Introduction Hydrolysed diets have been widely used in small animal practice in the past decade for the diagnosis and management of presumptive adverse food reactions. Potentially allergenic proteins must be large enough to bridge at least two IgE molecules on the surface of mast cells to elicit degranulation and consequent release of inflammatory mediators. 1 Protein epitopes are often con- formational and polyvalent, although sensitization to linear epitopes can occur. 2 The aim of hydrolysis is to break the peptide bonds in the amino acid chains to generate smaller peptide fragments from the protein molecule in order to reduce allergenicity and increase digestibility. 3 There are still controversies about the minimum molecu- lar weight of a potentially allergenic protein. Generally, major food allergen proteins in humans have a molecular weight ranging from 10 to 60 kDa, but there is evidence that in some cases this threshold can be lower than 1.4 kDa. 4 The molecular weight, however, is not the sole determinant of allergenicity. Several studies have been carried out to validate the efficacy of different hydrolysed products in the presump- tive diagnosis of canine adverse food reactions. 3,5–11 Although hydrolysed diets have been demonstrated to be useful in the diagnosis of dogs with suspected adverse food reactions, the majority of these studies do not address the issue of whether hydrolysed diets con- trol clinical signs in dogs hypersensitive to the parent protein, nor is it known whether adverse food reactions in dogs are necessarily mediated by IgE. Cave and Guild- ford 8 demonstrated the in vitro suitability of hydrolysed chicken proteins for the development of hydrolysed diets using sera of dogs sensitized to chicken proteins. Beale and Laflamme 5 measured changes in pruritus after feeding a soy hydrolysate diet containing corn- starch (Nestle Purina Veterinary diet HA-formula, Nestle Purina, St Louis, MO, USA) for 2 weeks to client-owned dogs with sensitivity to corn or soy. They reported that pruritus was reduced by 50% in soy allergic dogs (n = 4) and 80% in corn allergic dogs (n = 6). Jackson et al. 7 demonstrated that 3 ⁄ 11 (21%) of Maltese · beagle dogs with demonstrated sensitivity to corn and soy exhibited worsening of clinical signs when fed the same hydro- lysed soy diet, although the remainder of the dogs seemed to tolerate it well. Finally, six dogs with induced soy sensitivity were shown to tolerate ingestion of increasing amounts of hydrolysed soy with no ill effects. 10 These studies represent a small number of dogs and further investigations are required to better understand the efficacy of using hydrolysed diets for the diagnosis and long-term management of dogs with adverse food reactions that may involve sensitivity to the corresponding native protein. 358 ª 2010 The Authors. Journal compilation ª 2010 ESVD and ACVD, Veterinary Dermatology, 21, 358–366. DOI: 10.1111/j.1365-3164.2010.00871.x