The effect of breed on age-related changes in behavior and disease prevalence in cognitively normal older community dogs, Canis lupus familiaris

Abstract 

Variation in breed longevity in the dog has led to the inference that large dogs age at a faster rate than small dogs, possibly because of an increased oxidative load. Potential differences in behavioral aging (the rate of age-related decline in cognito-behavioral performance) across breeds represent a significant challenge to veterinarians and scientists. Using data from a large cross-sectional survey of older dog owners, we aimed to identify breed differences in behavioral aging in successfully aged dogs ≥8 years of age. Differences based on longevity (short-lived, <11 years; medium-lived, 11-13 years; and long-lived, >13 years), size (small-sized, <35 cm; medium-sized, 35-55 cm; and large-sized, >55 cm), and breed (pure vs. crossbred) were identified using binary logistic regression. Significant breed differences across longevity group were seen in 2 behavioral responses: dogs drinking >1 L/d (P = 0.001, maximum difference between groups = 16.4%) and dogs showing aggression (P = 0.006, maximum difference between groups = 15.1%). In purebred dogs, 8 responses (P < 0.001-0.008, maximum difference between groups = 8.4%-20%) showed significant differences across size group compared with 1 response, in crossbred dogs (P = 0.008, max difference between groups = 28.4%). Significant differences were observed across longevity group in the prevalence of arthritis (P = 0.014) and across size group in the prevalence of arthritis (P < 0.001) and blindness (P = 0.014). In medium-sized dogs, 2 age × breeding group interactions were seen in ingestive behavior (P = 0.037) and aggression (P = 0.028). In large-sized dogs, 1 age × breeding group interaction was seen in abnormal locomotion (P = 0.025). A consistent direction in the differences identified was not seen across all analyses. In general, these data did not suggest an increased rate of behavioral aging in large, short-lived dogs. It is possible that size-dependent aging affects body systems differently or, alternatively, owner’s management may differ between small and large dogs, resulting in differences in behavior.

Keywords: dog, ageing, behavior, longevity, size, breed