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Does body condition affect fertility and reproductive performance in the bitch?: Comparing reproductive performance of overweight/obese and lean bitches


To identify how body condition, exercise, and nutrition affect the reproductive potential of female dogs and the health of their puppies. More specifically,
  • To compare selected hormonal biomarkers during breeding, pregnancy, and the postpartum period between overweight/obese and healthy weight bitches, and correlate these biomarkers with overall reproductive and neonatal outcomes.
  • To help overweight/obese bitches reach their target ideal weight through a controlled weight loss and exercise program, and compare reproductive and neonatal outcomes between their first overweight and second lean pregnancy. 


Many breeding bitches in the U.S. are overweight or obese, likely due to overfeeding and reduced physical activity. Obesity negatively affects the function of almost all organ systems and shortens a dog’s life span; however, the effects of being overweight or obese on pregnancy, whelping, and puppy health are largely unknown. Obesity is known to cause chronic low-grade inflammation which may alter normal physiological and hormonal balances and lead to infertility, pregnancy disturbances, and birth complications. Neonatal outcome and puppy health may also be affected.

Our study aims to determine how body condition affects fertility and reproductive performance in bitches that are actively reproducing. We will investigate weight in conjunction with nutrition and exercise. 

We hope that the results of our study will help breeders and veterinarians make the best decisions about breeding, predict reproductive outcomes on an objective scientific basis, and implement and monitor nutritional, exercise, and management strategies to improve reproductive efficiency and bitch and puppy health.

This study is funded by a Nestle Purina Resident Research Grant.


  • Healthy, intact female dogs aged 2-5 years
  • Medium to large breed dogs, weighing at least 15kg (33lbs)
  • Weight unchanged for at least 6 months
  • Proven breeder or maiden with no familial history of infertility


  • Dogs fed homemade/ raw diets / fish supplemented diets
  • Current medical conditions
  • Dog taking medications other than flea/tick/heartworm preventatives
  • Dog taking certain dietary supplements

Study Design

All visits will take place at the Veterinary Teaching Hospital in Blacksburg, VA or as house calls.

Participants will be asked to participate in:

  • Our routine breeding management program (The decision for a bitch being bred is independent of the study)
  • 9 separate visits throughout gestation and after whelping
    • 2-3 visits are standard of care visits, provided to all breeding bitches as part of our routine breeding management program
    • 6-7 visits are for research sample collections and research-related imaging
  • Fitness tracking with a provided FitBark 2 activity monitor throughout the study
  • Weekly activity and nutrition journal maintenance throughout breeding, gestation and after whelping
  • Detailed monitoring of the whelping process
  • A commitment to rebreed on the following cycle or after one cycle break
  • A controlled weight loss program before rebreeding with a clinical nutritionist under our supervision (overweight participants only).

A complete appointment schedule will be provided to owners upon study enrollment.


The cost of all study-related visits and study-related sample collections is covered by the study, including physical exams, reproductive ultrasound exams, cystocentesis and urinalysis, blood collections and initial blood work (CBC, chemistry, thyroid panel, and urinalysis). Enrolled dogs also receive one large bag of Purina Proplan Sport 30/20 (feeding not required for study), pregnancy diagnosis ultrasounds, and pre-whelping x-ray.

Routine, standard of care visits and procedures are the owner’s financial responsibility. The study will also cover the progesterone interpretation fee (NOT the laboratory costs) during standard of care visits of the second breeding cycle for those that participate in the full study. All costs associated with whelping, including any complications that may arise, are the responsibility of the owner.  


Dr. Sam McCarter and Dr. Orsolya Balogh, Theriogenology
Office Phone: 540-231-4621 | Email:

If your query is urgent, please call the Small Animal Hospital on 540-231-4621 and ask for the theriogenologist on duty.

Related Materials

Recruitment flier