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To date, studies which examine the development of tolerance towards feed antigens in young dogs have not yet been conducted. Current knowledge regarding this issue is based primarily on conclusions by analogy drawn from nutrition studies with humans as well as other species. In the present study, the development of an oral tolerance towards feed proteins was investigated in a feeding trial using beagle puppies.
The hypothesis was that puppies receiving only one protein source from birth onwards may have different immune responses subsequent to the introduction of new protein sources compared to puppies receiving mixed protein sources.
The aim of this study was to confirm a possible influence on the immune system and digestibility by feeding two diets to the puppies, which differed principally in their protein sources (chicken vs. chicken + fish + soybean + cottage cheese). Therefore 16 beagle puppies from two different litters were divided equally in two feeding groups by sex and origin. At the third week of life, the puppies were fed with the respective food, which was followed by a cross-over of the two diets after ten weeks and another eight-week feeding period. Blood samples were taken for the evaluation of the hematologic and differential blood counts, flow cytometric analysis for the characterisation of CD3+, CD4+, CD8+, CD21+, CD5+/MHCII+ und CD4+/Foxp3+-T-lymphocytes and mitogen induced lymphocyte proliferation assay with PWM, Con A und PHA at the 3rd, 6th, 13th and 21st weeks of life. The digestive trials for the analysis of nutrients and minerals and the food associated lymphocyte proliferation assays (chicken-, fish-, soy-, pork protein and cottage cheese) were conducted at the end of each feeding period (13th and 21st week of life).
Differences between both feeding groups were neither verifiable immunologically nor in regard to digestibility. Merely after the cross-over, the stimulation indices for the food associated proliferation assay for the fish, chicken and soyprotein were sigificantly higher compared to before the cross-over, and accompanied by slightly dicreased amounts of
CD4+/Foxp3+-T-lymphocytes. The proliferation response towards cottage cheese increased only numerically (p < 0,1). Whether these results represent the first indications of beginning sensitization necessitates further investigation. As the results were observed for both groups however, it can be assumed that the increases in SI after the cross-over more likely reflect age-dependent effects than feed-dependent effects.
However as an side effect the litter-effect could be detected.
Statistical analysis of hematological and immunological parameters was performed using ANOVA and Mann-Whitney-U-Test by using general linear model procedures (univariate) with each feeding group as a factor. The analysis of the fecal scoring and the digestion trial for the two factors „group“ and „litter“ was performed using general linear model procedures (univariate, Scheffé). The level of significance was set at p < 0.05.
To obtain more information about the influence of different protein sources on the immune response, further investigations such as the measurement of feed antigen specific IgE antibodies and the cytokine IL-10 should be conducted. Furthermore, the number of puppy litters examined should be increased to avoid high variability.