The very first weeks are critical for every neonate, whatever the species. At a very early stage, every gram counts when it comes to survival. The same is true for our puppies and kittens. At the same time, gaining too much weight, or gaining weight too quickly, can be detrimental to future health. As such, it is important to monitor canine and feline neonatal growth, to identify risks and take action to prevent either short-term morbidity/mortality or long-term negative outcomes.
For some years now, vet practitioners have been able to refer to paediatric growth curves to monitor the growth of puppies and, more recently, kittens. Nevertheless, vets are missing a tool to follow and monitor the growth of puppies and kittens during the first weeks of life, while at the breeder’s home. As birth weight and early weight gain are critical factors when it comes to puppy and kitten survival, breeders need a simple and easy-to-use tool to track the weight of their animals. Further, as dogs and cats come in a huge diversity of sizes (breeds), breed-specific puppy and kitten neonatal growth reference curves are now being developed.
The high neonatal mortality rate
Despite trying to provide the best care for dogs and cats with the latest medical and nutritional innovations, the reality is that nearly 10 percent of puppies (Chastant-Maillard et al., 2017) and 16 percent of kittens (Fournier et al., 2017) will die before they are weaned.
The reality is that nearly 10 percent of puppies and 16 percent of kittens will die before they are weaned
Based on the latest research, it has been identified that birth weight and early weight gain are some of the main risk factors for early mortality. Studies have demonstrated that to reduce the risk, the weight gain between birth and day two should be positive (Mila et al., 2015), and around day 10 to day 12 the birth weight should have doubled (Moon et al., 2001).
Even for a given litter, huge variability in the weight of the puppies or kittens can be observed. Studies have shown that puppies with a birth weight in the first quartile were two-and-a-half times more at risk of early mortality (Delebarre, 2014). Several factors are known to impact birth weight, such as the breed, the sex or the litter size itself (Mugnier et al., 2020). This means that breeders need to closely monitor the body weight of their animals, and thus have a way to follow their growth and development.
Does one size fit all?
Due to the diversity within each species, it is not possible to consider a single growth chart: one for puppies and one for kittens. Indeed, growth patterns differ right from the start when pets weigh no more than 200g. Further, the birth weight and growth pattern can be extremely variable between one breed and another even within the same (adult) size category.
In the study conducted by Mugnier et al. (2018) and Mugnier et al. (2019), more than 19,000 puppies and 7,700 kittens from more than 400 French breeding facilities were followed during their first two months of life and their daily weight was reported. The data collection lasted for a period of approximately three-and-a-half years.
Based on the longitudinal monitoring of these individuals (over their neonatal and early paediatric periods) the research team developed reference growth curves to fit with each species, size category, breed (Figure 1) and even gender (Figure 2) when relevant (males being more robust than females). After a year of developing the optimal models, the reference growth charts were ready for validation.
The research team, supported by statisticians, started then to develop criteria to make the most of these neonatal growth curves to bring additional value to the breeders and vets when using them. Currently, there are neonatal reference growth curves for 119 dog breeds and 36 cat breeds.
With time and additional daily body weight recorded into the system, there is potential not only to increase the number of breed-specific growth charts, but also to fine-tune the existing growth charts: specifically, to go even deeper in the segmentation (ie geographical breed variation or specific breed line), if biologically relevant.
With time and additional body weight recorded into the system, there is potential not only to increase the number of breed-specific growth charts, but [to include] geographical breed variation or specific breed line
While the existing growth charts are standard (based on the monitoring of healthy individuals only), these new growth charts are references. Indeed, they are a factual description of the growth of a group of individuals, as was done, for example, in children in 2002 by the Center for Disease Control and Prevention (CDC) (Kuczmarski et al., 2002).
Neonatal puppies and kittens have limited expression of clinical signs when not healthy. Even with rigorous observation, it may be difficult for the breeder to identify a puppy that is not suckling enough (as the animal can be round the nipple but not actively suckling) or “behaving” differently due to pain, discomfort or pathologies. Weight monitoring is an indirect and very easy way to assess the health status of the animal.
The neonatal growth curve can be used to detect individuals with abnormal growth patterns suggesting a higher risk of mortality. Indeed, the growth pattern of individuals dying within the first week is clearly different from the growth pattern of those who will survive up to weaning (Gaillard, 2022). As such, while knowing the weight of a specific individual is important, it is critical to have a validated framework to compare the value to (either within or between litters, or even between breeding facilities). The growth curves (where the centiles are represented) are a validated template to report the weight, and follow growth and development. Any deviation of the growth pattern compared to the reference growth chart of the population should promote closer monitoring, and be one of the signals (in addition to other clinical signs) to visit the veterinarian.
Any deviation of the growth pattern compared to the reference growth chart of the population should promote closer monitoring
Using an adapted diet (colostrum and/or milk replacer) and feeding schedule the pet professionals will be able to closely monitor the patients’ weight gain and adjust the energy intake accordingly. When visiting the vet, it will make anamnesis easier: with the opportunity to have a look at not only the early growth pattern of the given individual but also the trends of its littermates.
Monitoring early weight gain is critical for domestic animals. Breed-specific neonatal reference growth curves are a simple and easy-to-use tool available for breeders, and soon for vet practitioners, to follow some aspects of the health of the young animals. Daily or alternate daily weight reporting enables early detection of potential abnormal growth trajectory or any health condition impacting directly or indirectly on the weight gain. This tool should be implemented in the day-to-day routine to help breeders address the high pre-weaning mortality rate that is still currently observed in puppy and kitten breeding facilities.