Low and very low birth weight in puppies: definitions, risk factors and survival in a large-scale population

Amélie Mugnier,Claude Saegerman,Sylvie Chastant-Maillard,Hanna Mila,Achraf Adib-Lesaux,Faouzi Lyazrhi,Florine Guiraud,Virginie Gaillard,Aurélien Grellet

doi:10.1186/s12917-020-02577-z

Abstract

BackgroundNeonatal mortality (over the first three weeks of life) is a major concern in canine breeding facilities as an economic and welfare issue. Since low birth weight (LBW) dramatically increases the risk of neonatal death, the risk factors of occurrence need to be identified together with the chances and determinants of survival of newborns at-risk.ResultsData from 4971 puppies from 10 breeds were analysed. Two birth weight thresholds regarding the risk of neonatal mortality were identified by breed, using respectively Receiver Operating Characteristics and Classification and Regression Tree method. Puppies were qualified as LBW and very low birth weight (VLBW) when their birth weight value was respectively between the two thresholds and lower than the two thresholds. Mortality rates were 4.2, 8.8 and 55.3%, in the normal, LBW and VLBW groups, accounting for 48.7, 47.9 and 3.4% of the included puppies, respectively. A separate binary logistic regression approach allowed to identify breed, gender and litter size as determinants of LBW. The increase in litter size and being a female were associated with a higher risk for LBW. Survival for LBW puppies was reduced in litters with at least one stillborn, compared to litters with no stillborn, and was also reduced when the dam was more than 6 years old. Concerning VLBW puppies, occurrence and survival were influenced by litter size. Surprisingly, the decrease in litter size was a risk factor for VLBW and also reduced their survival. The results of this study suggest that VLBW and LBW puppies are two distinct populations. Moreover, it indicates that events and factors affecting intrauterine growth (leading to birth weight reduction) also affect their ability to adapt to extrauterine life.ConclusionThese findings could help veterinarians and breeders to improve the management of their facility and more specifically of LBW puppies. Possible recommendations would be to only select for reproduction dams of optimal age and to pay particular attention to LBW puppies born in small litters. Further studies are required to understand the origin of LBW in dogs.

Highlights

Neonatal mortality is a major concern in canine breeding facilities as an economic and welfare issue
The average within-breed birth weight ranged from 161.9 g (SD: 34.2) for Maltese to 513.7 g (SD: 90.8) for German Shepherd (Table 1)
The overall neonatal mortality rate in the study population was 8.2% (406/4971; 95%Confidence interval (CI): 7.4–9), with 36% (146/406; 95% binomial confidence intervals (95%CI): 31.3–40.8) of deaths occurring between birth and 2 days of age

Summary

Introduction

Neonatal mortality (over the first three weeks of life) is a major concern in canine breeding facilities as an economic and welfare issue. Low birth weight (LBW) is known to be an important risk factor for puppy mortality and morbidity during early life [4–6]. Newborns with LBW have lower energy reserves, and less vigour and are at a disadvantage when competing to suckle and obtain colostrum. This results in reduced passive immune transfer. Body temperature after birth and the thermoregulatory capacity of LBWs are lower than in heavier neonates [8–11] These factors could explain the increased risk of mortality in LBW puppies

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