The role of birth weight on litter size and mortality within 24h of life in purebred dogs: What aspects are involved?

•Birth weight was influenced by maternal size, weight, age, litter size and breed.•Birth weight did not differ between live born and stillborn pups.•Low birth weight appears to predispose to early neonatal mortality.•Identification of underweight pups in need of neonatal assistance. In humans, scientific evidence emphasizes the role of birth weight on neonatal welfare, morbidity and mortality. In canine species, defining normal ranges of birth weight is a harder issue due to a great morphological variability in size, body weight and breed. The aim of this study was to correlate birth weight with litter size and mortality within 24h of life in 789 pups from 140 litters of purebred dogs and to investigate the aspects that might affect these factors. Birth weight was influenced by maternal size, weight and age (P