Diet Choice and Health Risks

Hello, Summarians!

Long-term studies are rare in veterinary medicine. I am super excited for our clinic to be part of the 4-year STAY study from Loyal. Another impressive study is the Dog Aging Project. A lot of valuable information has been collected, including one of the studies summarized below.

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Insulin Concentrations in Horses

This study explored how season, breed, age, and sex influence insulin concentrations in equids, using a large dataset of laboratory samples submitted from across the United Kingdom for the evaluation of insulin dysregulation. It confirmed that serum insulin concentrations vary significantly with these factors, which has important implications for the diagnosis and monitoring of insulin dysregulation and the prevention of hyperinsulinemia-associated laminitis. The study found that basal insulin levels and responses to oral sugar challenges were highest in winter, suggesting both a physiologic adaptation related to seasonal metabolic changes and possibly dietary influences. These findings align with evolutionary theories such as the thrifty gene hypothesis, proposing that elevated winter insulin responses promote fat storage and energy mobilization in times of nutritional scarcity. 

The data also indicated that insulin concentrations were generally lowest in the fall, consistent with increased insulin sensitivity during this time, potentially serving as preparation for the winter months. While dietary management may contribute to seasonal insulin fluctuations, endogenous regulatory mechanisms likely play a major role. Increased insulin secretion and decreased insulin sensitivity during winter were viewed as part of a circannual metabolic cycle, supported by comparative evidence from both equine and human studies. Additionally, the study highlighted that certain breeds, particularly ponies such as Shetland and Welsh, had naturally higher insulin levels, whereas athletic breeds like Thoroughbreds and Warmbloods had lower concentrations—possibly due to differing exercise levels, which affect insulin sensitivity. Donkeys deviated from the pattern seen in horses, with insulin concentrations peaking in spring and summer, warranting further species-specific research and assay validation. 

Sex and age were also significant factors: mares had higher insulin concentrations than stallions, and older animals showed elevated levels, consistent with known associations between age, PPID, and insulin resistance. Importantly, this study excluded fasting insulin values, instead focusing on basal insulin collected at varying times to reflect real-world dietary intake, which may yield more clinically relevant insights. 

Although the retrospective nature of the study and its reliance on laboratory submissions introduced potential biases, particularly overrepresentation of horses already diagnosed or suspected of endocrinopathy, the large sample size provided strong statistical power and a broader representation of the equine population. Limitations included incomplete data on pre-test feeding, variable sample handling, and unknown EMS or PPID status in individual animals. Nevertheless, the findings underscore the need to consider seasonal and demographic variables when interpreting insulin values and support the development of more refined diagnostic approaches for insulin dysregulation in equids. 

Lopes, A., Huber, L. and Durham, A.E. (2025), The Seasonality of Serum Insulin Concentrations in Equids and the Association With Breed, Age, and Sex. J Vet Intern Med, 39: e70089. https://doi.org/10.1111/jvim.70089

Bottom line — Seasonal and demographic issues can be an issue.

Diet Choice and Health Risks in Dogs

In recent years, dog owners have become increasingly interested in how nutrition affects healthy aging in their pets, leading many to explore alternatives to commercial pet food, such as homemade cooked and raw meat-based diets. The popularity of these alternative diets is often driven by a distrust of commercial products and a belief that home-prepared or raw diets are healthier and more natural. However, when not formulated with the help of veterinary nutritionists, homemade diets often lack essential nutrients. Raw diets, while perceived as biologically appropriate and beneficial by many owners, raise concerns among veterinarians about nutritional deficiencies, food contamination, and the risk of transmitting antimicrobial-resistant pathogens. 

Despite widespread adoption of these feeding practices, scientific evidence evaluating their health effects remains limited. The Dog Aging Project (DAP), a large-scale longitudinal study involving over 27,000 companion dogs, aimed to assess the relationship between diet type and a range of owner-reported health conditions compared to extruded diets. Dental or oral conditions were the most commonly reported, but no association with diet type was found. Although extruded diets with larger kibble sizes have been shown in veterinary studies to reduce plaque accumulation, the DAP relied on owner reports, which may differ from clinical assessments. Likewise, no association was found between diet type and skin conditions, despite some prior studies suggesting early-life raw feeding might reduce the risk of atopic dermatitis. These earlier studies did not consistently adjust for breed and also relied on owner-reported outcomes. 

Regarding gastrointestinal health, dogs on commercial raw diets showed a slightly higher likelihood of having GI issues compared to those on extruded diets, though the association was not statistically significant after correction. Interestingly, dogs fed homemade raw diets were less likely to have GI conditions, but again the findings did not meet statistical significance thresholds. Dogs on home-cooked diets showed a higher prevalence of GI, hepatic/pancreatic, and renal/urinary conditions, but this may reflect reverse causation—where owners switch diets in response to pre-existing health issues rather than the diet causing the condition. 

The study also found that dogs on commercial raw diets had a higher reported incidence of respiratory conditions. Possible explanations include environmental factors associated with active or multi-dog households and the high fat content of raw diets potentially contributing to gastroesophageal reflux and aspiration. However, breed was not controlled for in this analysis, which could have influenced results. 

There was no significant increase in infectious or parasitic diseases among dogs on raw diets, despite concerns about foodborne pathogens. In fact, suggestive but non-significant associations were observed between commercial raw diets and increased GI conditions and between homemade raw diets and decreased GI conditions. Other exploratory findings included potential associations between commercial raw diets and endocrine, cardiac, and orthopedic issues, as well as tumor conditions in dogs fed home-cooked or homemade raw diets. However, none of these reached statistical significance under stringent corrections and should be interpreted as potential directions for future study. 

This cross-sectional study is limited by its reliance on owner-reported data, the lack of dietary composition details, and the possibility of reverse causation. The study population may not reflect the broader demographic of dog owners, and analyses included only spayed/neutered dogs without accounting for the timing of neutering, which could influence certain outcomes. Nonetheless, as the Dog Aging Project continues collecting longitudinal and clinical data, future research may offer more definitive insights into how diet influences long-term canine health.

Ortiz, A.V., Luo, I., O'Brien, J., Murphy, M., Rollins, A.W., Kaeberlein, M., , Ruple, A., Kerr, K.F. and Tolbert, M.K. (2025), Association Between Diet Type and Owner-Reported Health Conditions in Dogs in the Dog Aging Project. J Vet Intern Med, 39: e70060. https://doi.org/10.1111/jvim.70060 

Bottom line — Interesting information.

Interdigital Cysts in Dogs.

Canine interdigital furunculosis (CIF) is a multifactorial and often recurrent inflammatory skin condition of the paws that presents a diagnostic and therapeutic challenge due to the similarity in lesion appearance regardless of underlying cause. Commonly associated with hypersensitivities, endocrinopathies, foreign bodies, and conformational issues, CIF frequently leads to secondary bacterial infections, most often involving Staphylococcus species, and may require prolonged antibiotic use. The chronic inflammatory response, driven in part by foreign-body reactions to keratin from ruptured hair follicles, often necessitates the use of anti-inflammatory medications such as glucocorticoids and ciclosporin. In recent years, adjunctive therapies like photobiomodulation have been explored, including fluorescence light energy (FLE) therapy, which uses a topical photoconverter activated by blue light to modulate inflammation and promote healing. 

This study evaluated the use of FLE in conjunction with systemic antibiotics for treating CIF, comparing it to antibiotic therapy alone. Results demonstrated that the addition of FLE significantly accelerated time to clinical resolution. By Week 4, half of the FLE-treated paws had healed compared to 17% in the control group, and by Week 8, healing was observed in 88% of FLE-treated paws versus 54% in the control group. While no significant differences were noted in numerical evaluation scores (NES), global lesion scores (GLS) were significantly lower in the FLE group at days 28 and 56, reflecting faster and more complete recovery. These outcomes align with prior studies suggesting FLE enhances epithelial regeneration and modulates cytokine activity, likely through mechanisms involving epidermal growth factor and matrix metalloproteinase-1. 

Adverse events were minimal, with no significant complications reported aside from expected mild, transient effects such as erythema or skin pigmentation changes. The study's split-body design allowed each dog to serve as its own control, improved internal validity, and reduced variability. However, the exclusion of multidrug-resistant infections and the omission of topical antimicrobials highlight limitations that should be addressed in future trials. 

In conclusion, the findings support the use of FLE as a safe and effective adjunct therapy in the management of CIF, significantly reducing time to healing and potentially lessening the need for extended antibiotic courses. 

Lange A, Mayer U, Bensignor E, Cornegliani L, Ferreira D, Matricoti I, et al. A blinded randomised split-body clinical trial evaluating the effect of fluorescent light energy on antimicrobial management of canine interdigital furunculosis. Vet Dermatol. 2025; 00: 1–11. https://doi.org/10.1111/vde.13340 

Bottom line — Promising treatment modality.

Just putting things in perspective …