Factors influencing birth weight and neonatal weight gain in Chow-Chow puppies

Introduction and aim. Abnormal birth weight (BW) and neonatal weight gain (NWG) are related to risk of neonatal diseases and mortality. In puppies, a physiological weight loss (<10%) in the first 24-48 h of age is reported (1); then body weight should increase constantly during the first weeks after birth. The BW and NWG are different among breeds of similar size (1), and might be influenced by several factors, such as maternal weight, litter size and neonatal gender. The availability of breed-specific reference values for BW and NWG are necessary for the correct management of normal newborns and for the prompt recognition of puppies underweighted at birth or that fail to growth. The aims of this study were: 1) to depict BW and NWG curve of Chow-Chow puppies; 2) to investigate factors influencing BW and NWG in this breed; 3) to assess possible relations between BW and alive or stillborn puppies, as well as between NWG and surviving or not surviving puppies. Materials and methods. Seven bitches of a single FCI kennel with a body condition score of 2.5-3/5 were involved in this study. Pregestational maternal body weight (PMBW) was assessed and all bitches were fed with the same commercial diet according to metabolic requirements for gestation and lactation. At whelping, BW of 69 puppies (18 litters) measured before the first suckling, litter size, newborn gender, and alive or stillborn puppies were recorded. All puppies were fed exclusively by maternal milk assumption. Neonatal body weight was daily (morning) monitored for the following 3 weeks of age. The effect of PMBW, litter size and newborn gender on both BW and NWG was evaluated. The relations between alive or stillborn puppies and BW, as well as between neonatal mortality and NWG were also assessed. All data were statistically analyzed by ANCOVA (p<0.05). Results. All puppies were born by spontaneous whelping, at term of normal pregnancies. At whelping, the litter size was 4±2.03 (mean ±SD). Stillborn accounted for 14% and neonatal deaths for 4%. Mean (±SD) of puppies BW was 403±75 g and PMBW was 32.7±1.78 kg with a ratio of 1.2%. Puppies BW was positively influenced (p<0.0001) by the PMBW. A daily weight gain curve was drawn plotting body weight and age: the exponential trend line resulted in y = 356.48e0.0707x (R² = 0.99). No significant weight loss was detected in the first 48 hours of age, a constant trend line of growth (p<0.0001) was instead observed from birth to the end of the study. Weekly growth trend line was positively influenced by PMBW (p<0.0001) and negatively by the litter size (p<0.001). In puppies of 3 weeks of age, the mean (±SD) body weight was 1.68 ± 0.46 kg and the ratio to PMBW was 5.3%. No significant differences in both BW and NWG were detected when the gender was considered. Similarly, BW and NWG were not significantly associated with alive/stillborn puppies or with neonatal survival/deaths. Conclusions. The definition of the birth weight and neonatal weight gain curve for specific breeds could contribute in the estimation of the healthy growth of puppies. In this study, Chow-Chow BW and NWG were defined and they were both influenced by PMBW, as previously reported in humans (2). Neither BW nor NWG were related with neonatal gender or death, although the association between lack of weight gain and neonatal death deserves further investigations. Acknowledgements. The authors wish to thank the Chow Chow FCI registered kennel “dei Leoni Imperiali” for data collection. References. 1) Hawthorne et al. J Nutr, 2004;134:2027S-30S. 2) Miletic et al. Coll Antropol, 2007;31:993-7.