Background: Genetic and environmental factors, including dietary copper intake, contribute to the pathogenesis of copper-associated hepatitis in Labrador retrievers. Clinical disease is preceded by a subclinical phase in which copper accumulates in the liver. Objective: To investigate the effect of a low-copper, high-zinc diet on hepatic copper concentration in Labrador retrievers with increased hepatic copper concentrations. Animals: Twenty-eight clinically healthy, client-owned Labrador retrievers with a mean hepatic copper concentration of 919 ± 477 mg/kg dry weight liver (dwl) that were related to dogs previously diagnosed with clinical copper-associated hepatitis. Methods: Clinical trial in which dogs were fed a diet containing 1.3 ± 0.3 mg copper/Mcal and 64.3 ± 5.9 mg zinc/Mcal. Hepatic copper concentrations were determined in liver biopsy samples approximately every 6 months. Logistic regression was performed to investigate effects of sex, age, initial hepatic copper concentration and pedigree on the ability to normalize hepatic copper concentrations. Results: In responders (15/28 dogs), hepatic copper concentrations decreased from a mean of 710 ± 216 mg/kg dwl copper to 343 ± 70 mg/kg dwl hepatic copper after a median of 7.1 months (range, 5.5–21.4 months). Dogs from a severely affected pedigree were at increased risk for inability to have their hepatic copper concentrations normalized with dietary treatment. Conclusions and Clinical Importance: Feeding a low-copper, high-zinc diet resulted in a decrease in hepatic copper concentrations in a subset of clinically normal Labrador retrievers with previous hepatic copper accumulation. A positive response to diet may be influenced by genetic background. Determination of clinical benefit requires further study.

The principle determinant of melanin derived hair colour and patterning in mammals is genetic, but environmental factors are now thought to play a role. It has been shown that the concentration of melanins in cat hair is influenced by the amino acid composition of their diets. Also, puppies were found to require tyrosine (Tyr) intake significantly greater than that recommended for normal growth and development in order to optimize melanin expression in their coats. Much of the work to date has been conducted in growing animals. Less is known about the relationship between nutrition and hair melanin deposition in healthy adult animals. In this study, we fed 2 groups of adult black Labrador retrievers (12 dogs/group) different concentrations of Phe + Tyr (5.6 vs. 3.5 g/Mcal) for 24 weeks and used spectrophotometric measurements every 8 weeks to detect any associated changes in the dogs’ hair colour. The higher intake dogs showed reduced dilution of their black coat pigment compared with the lower intake dogs. Specifically, following 16 weeks at the higher intake, the dogs showed less yellow pigmentation to their coats (P = 0.0032), and after 24 weeks at the higher intake, the dogs showed less red (P < 0.0001) and yellow (P< 0.0001), as well as greater overall dark pigmentation (P < 0.0001). In conclusion, we have demonstrated for the first time that colour expression in the hair-coat of adult dogs is dependent on dietary intake of Tyr, and that the requirement appears to be in excess of the minimum level recommended to maintain health.

Background: Canine atopic dermatitis (cAD) is a common chronic relapsing pruritic skin disease for which management commonly relies on life‐long use of immunomodulatory drugs. A number of the medications used are associated with adverse effects and the potential for complications during long‐term use.Hypothesis: The goal of the study was to determine if a complete and balanced diet formulated for therapeutic benefit could contribute towards management of cAD. We hypothesised that the diet would reduce pruritus while also reducing the requirement for medication during the study period.Animals, materials and methods: Forty privately owned dogs, having undergone a comprehensive diagnosis for cAD, were randomly allocated to two groups, each group being fed one of two diets (test or control) for up to nine months. We assessed pruritus, Canine Atopic Dermatitis Extent and Severity Index‐(4th iteration) and medication score, the latter reflecting the medication required to maintain a satisfactory quality of life for the animal.Results: Both diets were well‐accepted and ‐tolerated. There was a significant improvement in the pruritus score after three months of feeding the therapeutic diet (P = 0.0001). No such improvement was observed at any time point in the group of dogs given the control diet. There was a reduced drug requirement for dogs receiving the therapeutic diet after three months (P = 0.058), and that decrease was significant at six months (P = 0.021) and nine months (P = 0.018). No improvement was seen at any time point in the control group.Conclusion: The results suggest that a novel therapeutic diet can assist in the management of cAD by helping to control pruritus and reducing reliance on medication.

We investigated the effect of feeding a skin barrier function-augmenting diet early in dogs' lives on the appearance of clinical signs associated with canine atopic dermatitis. Pregnant bitches (starting 5 weeks after mating) and their subsequent litters (up to 1 year of age) were fed either supplemented or unsupplemented diets. Nutrients supplemented were nicotinamide, pantothenate, histidine, inositol and choline. Circulating IgE levels to dust mute allergens Der f and Der p were measured when the puppies were 6 and 12 months old. Two owner questionnaires were used to assess the occurrence of typical signs associated with atopic dermatitis when dogs were between the ages of 22 and 36, and 34 and 48 months. Using linear mixed models we observed higher levels of circulating anti-Der f (P = 0·021) and -Der p IgE (P = 0·01) during the first year in the dogs fed the unsupplemented than in those fed the supplemented diet. The owner-assessed incidence of atopic dermatitis signs amongst the dogs was significantly greater in the unsupplemented group at the time of the second follow-up questionnaire (10/33 dogs v. 2/24 dogs). These outcomes suggest that a nutritionally derived improvement to barrier function early in life may reduce the frequency of signs associated with atopic dermatitis. The effect is possibly the result of making the epidermis, now thought to be a major route of environmental allergen exposure, more resistant to penetration.

Dogs suffer from skin associated issues with a disproportionate frequency, with consequent interest in providing nutrition to optimize their skin's natural defences. Linoleic acid (LA) is known as an essential nutrient in dogs and plays a critical part in the lipid component of skin barrier formation. Minimum requirements have been defined, primarily based on eliminating signs of deficiencies such as dry, flaky skin and inflammation. Zn has been shown as an important nutrient for maintaining epidermal health. This pilot study investigated whether there are skin barrier benefits from feeding both linoleic acid and Zn at levels significantly in excess of published minimum requirements. Eight Labrador retrievers were fed a diet containing 3.8 g/Mcal LA, 21 mg/Mcal Zn for 12 weeks to establish baseline conditions for all dogs (basal diet). After this period, for a further 12 weeks, the dogs were switched onto a diet containing 7.9 g/Mcal LA and 50 mg/Mcal Zn (test diet). Transepidermal water loss (TEWL measurements) were used as a measure of skin quality and integrity and were taken at the end of the initial feeding period, and at 6 and 12 weeks of the test feeding period. TEWL was reduced by 8.11 g/m²/h (P < 0.001) six weeks after instigation of the test diet, and by 7.52 g/m²/h (P < 0.005) at 12 weeks, compared to the levels (14.73 g/m²/h) at the end of the basal feeding trial period. The results showed evidence of improved barrier properties as TEWL when feeding higher levels of LA and Zn for six and 12 weeks.