This study was designed to evaluate the impact of birth weight (reflecting intrauterine growth) and early growth rate (reflecting colostrum intake) on risk of neonatal mortality in puppies and to determine the critical thresholds of both parameters.

Puppies from various breeds (514 total) were weighed at birth and at two days of age, and the growth rate over that period (early growth rate) was calculated for all survivors (477 total). Linear mixed models evaluated the effect of birth weight on mortality between birth and two days of age and the effect of both birth weight and early growth rate on mortality between two and 21 days of age. Birth weight was influenced by litter size, with more low-birth-weight puppies in large litters compared with smaller litters. Mortality over the first two days after birth was associated with birth weight, with 81.1% of dying puppies characterized by a low birth weight. Mortality between two and 21 days of age was not related to birth weight but was found to be associated with early growth rate, with higher risk of death in puppies with growth rate at or below –4% after the first two days of life.

This study demonstrates the differential effect of intrauterine nutrition impacting mortality during the first two days of life and that of colostrum intake impacting mortality until 21 days of life. Birth weight and early growth rate thresholds provided in this study allow identification of puppies at risk, whereby provision can be made for adequate nursing to increase their chances to survive.

Source: H. Mila et al., 2015. Differential impact of birth weight and early growth on neonatal mortality in puppies. J Anim Sci online, August 2015. doi: 10.2527/jas.2015-8971.