Effects of zinc source and enzyme addition on the faecal microbiota of dogs

In a recent study by Pereira et al. (2021), researchers investigated the impact of two different zinc sources—zinc sulphate and zinc proteinate—on the faecal microbiota of adult Beagle dogs. Additionally, the study examined whether the inclusion of a multi-enzymatic complex derived from Aspergillus niger fermentation affected the microbiota. This experiment was motivated by previous findings that organic zinc sources may be more bioavailable than inorganic ones, which could be further influenced by dietary constituents like phytates. However, little was known about how these zinc sources and enzyme additives interact with the gut microbiota of dogs.

The study employed a rigorous experimental design using 12 Beagles arranged in three independent 4 × 4 Latin Squares over four periods. The four diets varied in zinc source and enzyme addition: two diets provided zinc sulphate (with and without enzyme) and two provided zinc proteinate (with and without enzyme). The researchers aimed to understand how these variables influenced microbial diversity and the abundance of specific bacterial taxa.

Key findings from the research showed that zinc source significantly influenced the bacterial composition of the dogs' faecal microbiota. Organic zinc (proteinate) was associated with a higher abundance of beneficial Firmicutes, while inorganic zinc (sulphate) was linked to increased levels of Proteobacteria and Bacteroidetes, bacterial phyla often associated with gut inflammation and dysbiosis. At the genus level, dogs fed zinc proteinate had a higher abundance of Turicibacter and Paraburkholderia, whereas those fed zinc sulphate showed increased levels of Campylobacter, a potential pathogen. These results suggest that the bioavailability of zinc from organic sources may reduce the proliferation of harmful bacteria compared to inorganic sources.

Interestingly, the addition of the multi-enzymatic complex had a limited impact on overall microbial diversity but did increase the abundance of Lactobacillus, a beneficial genus linked to gut health. This effect was more pronounced when organic zinc was combined with enzymes, which led to increases in certain beneficial bacterial groups such as Actinobacteria and Firmicutes. However, the enzyme addition did not affect faecal fermentation products such as volatile fatty acids (VFAs), lactate, or ammonia, indicating that its impact on the gut microbiota may be more subtle and related to microbial composition rather than functional output.

The study concluded that while zinc source significantly affects the composition of the gut microbiota, the addition of enzymes appears to have a more modest influence. Organic zinc was shown to favour beneficial bacterial groups, whereas inorganic zinc may promote potentially harmful bacteria, such as Campylobacter. These findings highlight the complexity of nutrient interactions in the gut and the potential benefits of using organic zinc supplements in canine diets. Further research is needed to explore the long-term implications of these changes on canine health and the interaction between zinc sources, enzyme supplementation, and gut microbial communities.

This research fills an important gap in understanding how different forms of zinc and enzyme supplementation influence the gut microbiota in dogs, providing a foundation for future studies on dietary interventions aimed at improving canine gut health. The authors suggest that more studies are required to fully elucidate the relationship between zinc bioavailability and microbial composition and its implications for overall health.