Understanding early risk factors for diseases in adult dogs: What we know so far and what future research should study

Understanding early risk factors for diseases in adult dogs: What we know so far and what future research should study

Virginie Gaillard, Sylvie Chastant, Gary England, Oliver Forman, Alexander J. German, Jan S. Suchodolski, Cecilia Villaverde, Pascale Chavatte-Palmer, Franck Péron. Environmental risk factors in puppies and kittens for developing chronic disorders in adulthood: A call for research on developmental programming. Frontiers in Veterinary Science, 9 (2022).

Link (open-access): https://doi.org/10.3389/fvets.2022.944821

Summary by: Noah Stetson

This article:

• Identifies three important long-term health problems in adult dogs (obesity, chronic enteropathy, and behavioral problems)
• Discusses possible factors in the early stages of a puppy’s life that might make them more likely to develop these problems as adults (mostly based on a small number of correlational studies)
• Lists what the most important research priorities are for preventing these problems from occurring in adulthood before they occur (when the puppies are very young)

Because dog breeders have control over a large part of their puppies’ environment when raising them, breeders could play an important role in preventing these problems from occurring when their puppies become adult dogs.

Background

Many dogs go on to develop chronic health problems that negatively impact their well-being and the well-being of the humans they live with. The article looks at what we know so far about the early-life risk factors for puppies that might make them more likely to develop these health problems as adults and suggests what research topics are most important to prioritize moving forward so we can better understand how to prevent puppies from facing these chronic health problems in adulthood. The full article covers health problems in both dogs and cats, but this summary focuses on dogs.

The health problems the authors focus on in this paper are obesity, chronic enteropathy (a catch-all term for chronic intestinal issues), and behavioral problems. They chose these conditions because they are common, hard to treat, and can be detrimental to a dog’s well-being and longevity.

Data & Methods

This paper is a literature review, which means the authors looked through previous research to see what we know so far and what “gaps” there are in our knowledge about these topics.

The authors searched for research papers on the website PubMed in the summer of 2022, looking for papers about epigenetics, developmental programming, and developmental origins of health and disease in dogs. The authors ended up finding 51 relevant articles about dogs, noting that there has been “inadequate consideration” in research on how the environment in early development relates to a dog’s physical and behavioral traits in adulthood.

Results

The findings of the study are split by health problem (obesity, chronic enteropathy, and behavior problems), with a summary of potential early risk factors the authors identified, and what topics the authors think are most important to prioritize in future research.

What do the authors mean by “potential early risk factors”?In the context of this paper, a “risk factor” is something that increases the likelihood of developing a disease“Potential risk factors” are factors that the authors think might be risk factors based on some previous research, but more research is needed to determine whether this is actually the caseIt is important to know that almost all of the research the authors cite are from in the paper are correlational studies, so while a potential risk factor may have been shown to correlate with being more likely to get a certain disease, that doesn’t necessarily mean the risk factor is what is actually causing itThis fun website shows some excellent examples of how different factors can correlate with each other without one directly causing the other. Play around with it and see what wacky correlations you can find!

Obesity

Obesity is very widespread in dogs. About 8-19% of dogs are estimated to be considered “obese”, and 37-56% are estimated to be overweight. Obesity is a big problem in dogs because it can lead to many different health problems, such as type 2 diabetes, cardiovascular diseases, joint problems, and cancers. In dogs, being overweight and being obese are linked to having a shorter lifespan and a poorer quality of life.

Potential early risk factors for obesity:

• Low birth weight
  • Findings are mixed. One study (in Labrador retrievers) found low birth weight to be associated with dogs being overweight as adults, while another (in beagles) found no correlation between birth weight and risk of being overweight in adulthood
• Higher growth rates
  • One study (beagles) found that fast growth rate from birth to just 2 weeks of age could predict whether a dog ended up being overweight as an adult
• Spaying and neutering (“altering”)
  • We currently don’t have enough information to know what age is best to alter and how this differs between male and female dogs
  • One study found that golden retrievers altered at age 6-12 months were 42% more likely to be obese as adults, compared to dogs altered over the age of 1. However, the same study didn’t find a significant difference in rates of obesity between dogs altered before 6 months and dogs altered over the age of 1.
  • The hormonal changes from altering dogs can contribute to obesity by lowering the number of calories a dog needs to consume and by increasing their appetite.
  • Altering a dog before they’re fully grown can also cause them to grow at a faster rate

Research priorities for obesity:

• Nutrition
  • How nutrition in utero can affect the likelihood of obesity later in life
  • Determine whether low weight is a risk factor for obesity by contributing to the metabolism slowing down to compensate for the lack of calories in early development
  • Effects of maternal nutrition and milk quality and milk quantity on adult body weight and metabolism
• Growth
  • How energy balance while growing is associated with body composition later in life
    • Using a large and diverse group of dogs
  • Body Composition Scores are made for adult dogs, so it’s difficult to discern whether a puppy should be considered overweight
    • Studies can compare dogs in their study to newly available growth rate standards for puppies 12 weeks and older
• Gut Microbiota
  • Whether the gut microbiome in puppies is associated with them being obese as adults, and whether early nutrition could influence it
• Spaying and neutering
  • The impact of spaying and neutering at different developmental stages
    • Looking at sex and breed differences too

Chronic Enteropathy

“Chronic Enteropathy” is a catch-all term for many different chronic inflammatory intestinal disorders, previously called “Inflammatory Bowel Syndrome” (IBS) or “Inflammatory Bowel Disease” (IBD). Chronic enteropathy can be associated with immune problems, food, and bacteria. There are very few studies available on early-life risk factors for chronic enteropathy, so more research is needed.

Potential early risk factors for chronic enteropathy

• Getting parvo as a puppy, especially very severe parvo
• Spaying/neutering, especially in female dogs

Research priorities for chronic enteropathy

• Association between gut microbiome in puppies and risk of chronic enteropathy as adults
• Development of normal and abnormal gut microbiome in puppies and its association with chronic enteropathy
• Association between early diet and its risk/prevention of chronic enteropathy
  • Pre- and probiotic supplementation in dams during pregnancy

• Antibiotic use (in puppies and pregnant adults) and risk of developing chronic enteropathy
• When studying chronic enteropathy, researchers need to use nutritionally specific diets (instead of just saying the dogs in the study were all fed “a commercial dog diet”, etc.) and record only veterinarian-diagnosed chronic enteropathy

Behavioral Problems

“Behavioral problems” are very common in dogs and can significantly affect a dog’s quality of life, relationship with humans, and ability to perform jobs they may have been selected for (e.g., disability assistance). Common behavior problems include aggression towards humans and other animals, separation anxiety, and house soiling. Behavior problems are reported to be the main reason for 10% of dogs being surrendered to shelters.

Potential early risk factors for behavioral problems:

• Malnutrition
• Poor maternal
  • What is “good” maternal care”? Studies on this have been mixed. What makes for “good” maternal care might depend on the dog. Guide dogs might benefit from attentive, but relatively less-involved mothers, while other dogs might benefit from more-involved mothers.
• Poor socialization for puppies under 3 months old
• Dogs from high-volume commercial breeders sold online or through pet stores
  • One study found that aggression was the most common behavior problem associated with dogs from this type of breeder
  • Potential factors thought to contribute to this:
    • Increased maternal stress
    • Receiving too little or too much neonatal stimulation
    • Early weaning
    • Early maternal separation
• Lack of socialization with other dogs in the first 8 weeks of life
  • Associated with aggression toward unfamiliar dogs at 1-3 years of age
• Lack of socialization to humans
• Being attacked or “threatened” by an unfamiliar dog
  • Associated with “dog-directed fear” and “stranger-directed aggression” at 1 year of age
• Epigenetic changes
  • For example, methylation of the promoter region of the oxytocin receptor gene
    • In female dogs, higher methylation is associated with a greater likelihood of “appeasing behavior” in a “threatening approach” test, but with a lower likelihood of “appeasing behavior” in male dogs.

Research priorities for behavior problems:

• Include assessments in-utero

• More studies of environmental risk factors for adult behavior problems in dogs aged 6-12 months
• How the prenatal and early postnatal environment contribute to behavior problems in adulthood
  • Differences (if any) between males and females
• Effect of the periconceptional period (time before conception and at the very beginning of conception) on behavior problems
• Timing of environmental exposures on later adult behavior
• Role of placenta on behavior problems
• Paternal influences on offspring’s epigenome, breed, and genetic variation
• Important to access large datasets that cover the entirety of the lifespan
• Large cohorts following pet dogs throughout their lifespans to identify individual differences
  • Ideally also using data from the breeders of the puppies, the sire, and the dam
  • Service dog organizations could be a good way to get this data
• Epigenetic mechanisms linking early-life experiences to adult behavioral problems

A caveat:

The potential risk factors the authors identified have not necessarily been shown to “cause” a certain disease. Past research on this topic is very limited, and most of the studies the authors cited studied correlations only, so we should consider the “potential risk factors” identified by the authors of this paper as starting points that require further research to determine whether they actually contribute to increased risk of disease.

While there are some aspects of a dog’s health in their adult life that breeders don’t have control of, there are many aspects of an adult dog’s health that are thought to be affected by their environment as a young puppy, sometimes even before they are born. There is still a lot to learn about how a puppy’s early environment affects their health in adulthood. Breeders, researchers, veterinarians, and puppy families can work together to help bridge this knowledge gap.

This work by the Functional Dog Collaborative is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.