Puppies are less well developed at birth than many other species, and high mortality rates are not uncommon in the first two weeks of life. A newborn puppy is at risk of hypoxia, and can develop hypothermia (due to its poor thermoregulatory function) and infection (due to an immature immune system). Other problems, such as dehydration and hypoglycemia, can also cause morbidity and mortality. Intensive care of the newborn must therefore be aimed at preventing the main trigger factors (Figure 1) and this short paper offers the clinician advice on how to maximize puppy survival. 

Initial care 

At birth, the dam will usually rupture the fetal membranes, cut the umbilical cord, and lick the puppy’s chest to stimulate respiratory movements, before cleaning and drying the puppy. However, if the dam is negligent or inexperienced, human intervention is necessary. This involves using a clean, dry swab to remove all fluid from the nose and mouth, while simultaneously rubbing the chest to stimulate respiration. The puppy must be held horizontally on the palm of the hand, holding the head to protect it; sudden movements, or shaking or swinging the puppy, should be avoided. If necessary, amniotic fluid in the nasal passages can be removed by specialized suction pump, and the newborn must be dried to prevent hypothermia.

Neonatal clinical evaluation

The Apgar score is a prognostic guide for neonatal survival, with the highest mortality levels in animals having a low score. To be considered healthy, the puppies must score 7 or above at five minutes post-partum; this is the critical time for reliable assessment, as some pups will have a lower score immediately after birth due to temporary suppression of vital functions. Neonates scoring between 4 and 7 require assistance and those with a score below 3 require emergency care. 

Adequate maintenance of body temperature is vital, as the thermoregulatory reflexes (vasoconstriction and shivering) are non-functional at birth. A puppy’s body temperature should be 35-36ºC (95-96.8ºF) in the first week and 37-38ºC (98.6-100.4ºF) in the second and third weeks of life. Ambient temperatures below 27ºC (80.6ºF) cause hypothermia, while temperatures exceeding 33ºC (91.4ºF), along with high levels of relative humidity (85-90%), predispose to respiratory problems. Suckling helps a puppy to stay warm, as the dam’s milk is 3-4ºC (37.4-39.2ºF) above body temperature.

If the bitch cannot keep the litter warm it is necessary to check each puppy’s rectal temperature (using a small-diameter digital thermometer) at least once a day and provide an external heat source, either by incandescent lamps (20-40W) in the whelping box, or devices such as heat pads or warming bags (Figure 4). Ambient temperature must be monitored to prevent excessive heat, burning and dehydration.

Hypothermia adversely affects immunity, digestion and maternal care. With low temperatures a puppy loses its sucking reflex, resulting in reduced energy intake and general weakness. A hypothermic puppy must be warmed slowly (over 1 to 3 hours) to avoid peripheral vasodilation and hypoxia of vital organs; this should be followed by fluid therapy if necessary. Feeding must only be established after normothermia has been reached. 

After ensuring respiration and thermal maintenance, each puppy should be examined for any birth defects such as hare-lip and cleft palate (Figure 5), umbilical hernia, anal atresia and skull disorders (e.g., an open fontanelle).

Body weight

Although many factors can affect birth weight (e.g., age and health of the mother, placental effectiveness, litter size, and nutritional, infectious and environmental reasons), it is an important indicator for survival in most domestic species. Each puppy should be precisely identified and weighed regularly using digital scales (Figure 6). The birth weight can vary with breed and litter size but is typically between 100-200 g for a small breed puppy, 200-300 g for medium-sized breeds and 300-500 g for large breeds. Estimating the weight trend allows reliable monitoring of a puppy’s development and may enable early detection of abnormalities. Body weight may drop in the first day of life (up to 10% of birth weight) due to dehydration, but after this point neonates should gain 5-10% of their birth weight daily, so that by day 15 the puppy will weigh around double its birth weight.

Natural or artificial lactation

During the first week of life, puppies will suckle every one or two hours and sleep the rest of the time. The mother licks them periodically to stimulate urination and defecation. If the mother is healthy and well nourished, her milk will satisfy the litter’s needs for the first three to four weeks of life. However, if there is insufficient milk production (e.g., following death of the dam, agalactia or mastitis) milk substitutes – either commercial or homemade – are necessary, with a formula that provides for the species requirements. Nevertheless, puppies given milk substitutes may not have the same growth rate when compared with those fed by natural lactation. 

Milk substitutes may also be required for puppies with low body weight at birth (typically if at least 25% less than the average expected for that breed), for newborns that lose more than 10% of their initial weight in the first 24 hours of life, or where puppies do not double their birth weight within the first two weeks of life. 

Neonate puppies use fat, rather than lactose, as an energy source, so a dam’s milk has a high lipid content; cows’ milk is unsuitable, as it is lactose-rich and low in fat and protein. The daily energy requirement of neonates is approximately 20-26 kcal/100 g body weight, but most commercial milk substitutes contain only 1 kcal/mL. Given that the maximum capacity of a neonate’s stomach is approximately 4 mL/100 g of body weight, it is possible to estimate the daily requirements and feeding frequency required. 

A milk substitute can be offered, either using an appropriately sized feeding bottle, or by orogastric tube, depending on the puppy’s health and if there is a vigorous sucking reflex. A feeding bottle stimulates the sucking reflex (and reduces the risk of aspiration) with the puppy held horizontally to maintain a near-natural feeding posture, without excessive stretching of the neck. Using an orogastric tube requires skill and risks intra-tracheal placement, and is more suitable if a large number of puppies require feeding, or if a puppy has poor sucking strength or inadequate weight gain. Monitoring is essential for puppies that require assisted feeding, to check for signs of overfeeding such as milk at the nostrils, regurgitation, abdominal discomfort and distension, and diarrhea; the latter sign can also be indicative of changes in the microbiota or even septicemia. Excessive feeding is considered to be one of the main causes of non-infectious diarrhea in puppies, but a weak sucking reflex, persistent whining, lethargy, and insufficient weight gain are indicative of inadequate milk intake.

Dehydration and hypoglycemia 

80% of a puppy’s body weight at birth is water; this, combined with other innate factors (e.g., a relatively large body surface area, permeable skin, and poor renal function) contribute towards the risk of dehydration in neonates, but dehydration is normally linked to prematurity, diarrhea, pneumonia, high ambient temperature or inadequate nursing. Hydration status can be assessed by observing the urine; a sample may be obtained by gently massaging the foreskin or vulva with wet cotton wool. A yellowish color indicates dehydration, while dilute, translucent urine is normal. Dehydrated animals may also have dry, pale oral mucosae.

Rehydration via warmed (37ºC/98.6ºF) fluids may be necessary (60-180 mL/kg/day). Oral administration is preferable as long as intestinal function is normal and the animal is not hypothermic. However, the subcutaneous route is often used, while intravenous or intraosseous administration is more suitable for giving small volumes of fluid. The therapeutic challenges when treating neonates are considerable, and conservative administration rates and close monitoring during therapy may be beneficial. Signs of overhydration include a serous nasal discharge, ascites, tachypnea/dyspnea and pulmonary edema. 

Dehydration may be accompanied by hypoglycemia. Because of low body fat reserves, limited gluconeogenesis and hepatic immaturity, a neonate must feed frequently in order to maintain normal glucose levels. Therefore, fasting for more than 2-3 hours may lead to hypoglycemia (< 35-40 mg/dL), which is manifested by lack of co-ordination, weakness or coma. Immediate treatment is essential, with slow administration of 5-10% dextrose solution into a jugular vein (at 2-4 mL/kg). If there is a poor response, additional doses can be given but blood glucose levels should be checked before administration due to the risk of hyperglycemia. 

Immature immune system 

Newborn puppies have an underdeveloped immune system and are completely dependent on the transfer of antibodies via the colostrum, which should be within a few hours of birth. There is considerable correlation between puppies with a low serum immunoglobulin level at two days of age and the neonatal mortality rate. Determination of serum alkaline phosphatase (AP) and gamma-glutamyl transferase (GGT) levels can confirm if a puppy has taken colostrum after birth. For animals with low enzyme levels, it may be helpful to give serum or plasma from vaccinated adults of the same species, either orally if the puppy is less than 24 hours old, or subcutaneously in “bolus” form if older than this; note however it is important to test serum compatibility before administration. 

Conclusion

Stimulated by the increasing emotional and financial value of pets, and the general vulnerability of animals in the post-partum period, specialized neonatology knowledge has developed greatly in recent years. Whilst proper handling of the parturient dam and her puppies is still the prime measure in combating neonatal problems, early identification of problems in young puppies allows for rapid intervention and application of appropriate intensive care therapies, leading to increased survival rates.