# Effects of Blueberry Consumption on Preference, Digestibility, and Oxidative Balance in Dogs

## TL;DR

This study explores how adding blueberries to dog diets affects their health, finding a potential protective effect against heat stress.

## Contribution

The study introduces blueberries as a natural dietary supplement for dogs, showing a possible protective effect against heat stress.

## Key findings

- Dogs preferred blueberry diets over other natural ingredients like Fucus algae or clove.
- Blueberries had minimal impact on digestibility, except for cellulose.
- Blueberry-fed dogs showed lower creatine kinase levels at rest during summer, suggesting protection against heat stress.

## Abstract

Dog owners are increasingly concerned about the impact of diets on their pets’ health, driving demand for natural alternatives. This study investigated the effects of adding blueberries to a wet commercial diet on oxidative balance in dogs subjected to a controlled exercise. Blueberries were selected over other natural antioxidant ingredients, such as Fucus algae or clove, due to their superior palatability and minimal impact on digestibility. To evaluate its effects on oxidative status, dogs were fed either a control diet or the same diet containing blueberries for 4 weeks. Animals performed two treadmill exercises to induce oxidative stress, at the start and end of the experimental period. Blood biomarkers of muscle activity, inflammation, and oxidative status were analyzed. The trial was conducted in both summer and winter. Exercise significantly influenced markers of muscle activity, oxidative stress, and antioxidant enzymes, with more pronounced responses in summer, suggesting a relevant impact of the environmental temperature. No significant differences in biomarker responses to exercise were observed between diets. However, lower creatine kinase levels were found at rest in the blueberry-fed group during summer. These results may indicate a protective effect of blueberries against heat stress, warranting further investigation.

The growing awareness of the diet–health connection drives interest in natural dog diets, which replace synthetic additives like antioxidants with natural ingredients. In Trial 1 of this study, preference for diets containing powdered Fucus algae (1.5%), powdered clove (0.45%), or whole blueberries (3%) was evaluated using the two-bowl method. Dogs exhibited a clear preference for the blueberry diet. In Trial 2, the impact of blueberries on apparent digestibility was assessed. Twelve Beagles were fed either a control diet (CON) or the same diet with 3% blueberries (BLU). No differences were observed, except for cellulose digestibility. Trial 3 evaluated the effect of blueberries on oxidative status during submaximal exercise. The same dogs were fed either CON or BLU diets for 4 weeks, with eight dogs completing treadmill exercises at the start and end of this period. Blood samples were collected before and after exercise. Trial 3 was replicated in summer and winter, reversing diet groups. Exercise increased creatine kinase (CK), urea, and malondialdehyde and decreased glutathione peroxidase, with stronger effects in summer, suggesting heat stress. Although the BLU diet did not mitigate exercise-induced changes, lower resting CK levels after 4 weeks in summer suggest protection against heat stress, warranting further study.