Puppy growth rate during early periods of labrador retriever development: role of litter size and photoperiod of birth

Several studies have recently investigated the birth weight of puppies from different pure-bred dogs. In general, birth weight decreased with litter size but there has been limited investigation into factors influencing growth during early development. The first month of life includes three stages of puppy development: neonatal (0-13 days), transitional (14-20 days), and first week of socialisation period (21-28 days). The aim of this study was to evaluate bodyweight and growth rate of 120 Labrador Retriever (LR) puppies during early development. Puppies from 19 show-line bitches under standardised composition of diet during pregnancy and lactation were involved in this study. Puppies were weighed weekly from birth to 28 days using an electronic digital balance. Relative weight gain (ΔW) was calculated for the neonatal period [ΔW 1 = (W day14 -W day0 )/W day0 ], transition period [ΔW 2 = (W day21 -W day14 )/W day14 ] and first week of socialisation period [ΔW 2 = (W day28 -W day21 )/W day21 ]. The effects of covariates on ΔW were assessed using generalised linear mixed models. Sex and photoperiod had no impact on relative weight gain, whereas litter size had a significant effect at ΔW 1 (p