September 30, 2017

How Does Your Dog Measure Up? New Growth Charts Could Provide the Answer

Evidence-based growth standards for dogs may help in monitoring early-life growth, identify potential growth disturbances, and promote long-term health.
By JoAnna Pendergrass, DVM
An optimal growth pattern during the growth phase helps set the stage for long-term good health. In humans, it is known that a suboptimal growth pattern due to malnutrition or a developmental disorder can lead to future health problems, such as obesity. Growth standards, which represent an ideal growth pattern, are a staple in human pediatric medicine and allow pediatricians to monitor an individual child’s growth and development.

In veterinary medicine, though, “there is limited information and little current guidance available on what constitutes optimal growth in dogs,” wrote the authors of a recent study on canine growth standards. The diversity of dog breeds and highly variable growth patterns of those breeds have made the development of a single canine growth standard a challenge, they noted.

The study, published in PLoS ONE, described how the author’s successfully developed evidence-based growth standards for male and female dogs based on size. Such standards, they believe, “could form the basis of a clinical tool to enable trained veterinary professionals to monitor growth objectively during early life.”

For their retrospective study, the authors collected age and body weight data, dating back to 1994, from over 6 million dogs that had visited Banfield pet hospitals throughout the United States. Study-eligible dogs met the following criteria:
  • Purebred
  • <3 years old
  • Normal body condition score (BCS)
  • Confirmed body weight and neuter status
  • Seen for routine preventative care or received a “healthy” diagnosis
BCS data from 2010 onward reflected use of the 5-category BCS scale, which was adopted in 2010. However, because most of the study’s data used the original 3-category scale (thin, normal, heavy), all 5-categrory measurements were converted to the 3-category scale.

Growth Curve Development
In a multistage process, the authors developed over 100 growth curves based on neuter status, breed, and adult size. The curves covered 12 weeks to 2 years of age.

Neuter Status
Neutering is a known risk factor for weight gain, particularly when performed during the growth phase. Authors observed an upward growth trajectory with early neutering (before 37 weeks) and a downward growth trajectory with later neutering (after 37 weeks). “Whether such shifts are the cause or the effect of age of neutering is not known,” the authors stated, warranting further study.

Notably, these shifts were small relative to interdog variability in growth patterns, suggesting that separate growth standards based on neuter status are not necessary.

Breed and Adult Size
The authors then created and compared breed- and size-specific growth curves for males and females. For the size-specific growth curves, the authors initially grouped breeds into 5 pre-existing size categories: toy, small, medium, large, and giant. However, because some breeds had growth patterns inconsistent with their size category, the authors created a sixth size category, renamed the categories I through VI, and readjusted the per-category weight ranges.

Growth patterns varied widely for category VI, which contained great Danes, mastiffs, and Rottweilers, making it unfeasible to create a growth curve for this category.

The authors observed overall agreement between the breed-specific curves and corresponding size-specific curves I through V, suggesting that size-based curves are useful for individual breeds and potentially mixed breeds. Breed-based curves, the authors noted, are too complex to be clinically useful.

Looking Forward
Further study will be needed to validate this study’s growth standards and create a growth standard for dogs with adult weights exceeding 40 kg. In addition, veterinary professionals will need training on using these growth standards.

Such standards, the authors believe, will help veterinary professionals objectively monitor early-life growth, identify potential growth disturbances, and promote long-term health.

Dr. JoAnna Pendergrass received her Doctor of Veterinary Medicine degree from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, a medical communications company.

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