The first two weeks of life is the period of greatest risk for newborn pups. Unfortunately, some early neonatal deaths are due to lack of advance preparation – especially failure to provide adequate heat in the whelping quarters, failure to vaccinate the dam (which gives neonatal infections a foothold), and failure to provide the dam with an adequate diet during pregnancy. These deaths are preventable.
Maternal factors are critical to puppy survival. Novice, obese, and elderly dams have higher puppy mortality rates than do experienced, well-conditioned, and younger dams. The quantity of the mother’s milk is also of utmost importance. Genetic influences may play a role, but in most cases milk supply is insufficient because the dam has not been fed enough calories. This is especially true for dams with large litters.
Congenital and acquired birth defects are infrequent causes of newborn deaths. Cleft palate, often accompanied by harelip, prevents effective nursing. Large navel hernias allow the abdominal organs to protrude. Heart defects can be severe enough to produce circulatory failure. Other developmental disorders that may be responsible for neonatal deaths include hemophilia, esophageal atresia, pyloric stenosis, anal atresia, and malformations affecting the eyes and skeletal system.
The Physiologically Immature Puppy
An immature puppy is at a distinct disadvantage because of his low birth weight and lack of muscle mass and subcutaneous fat. This pup may be unable to breathe deeply, nurse effectively, and maintain body warmth. His liver–brain ratio may be less than 1.5:1. His birth weight will be 25 percent below that of his littermates. Such a puppy is likely to be crowded out by his brothers and sisters and forced to nurse at the least productive nipples.
A common cause of immaturity is inadequate growth while in the uterus. The fault may be placental insufficiency, perhaps due to overcrowding or a disadvantageous placement of a placenta in the wall of the uterus. These puppies are immature because of their development rather than their age, and are at risk of developing cardiopulmonary syndrome.
Cardiopulmonary Syndrome
This is a shocklike state of circulatory failure that occurs in puppies under 5 days of age. Many affected puppies are physiologically immature. Inadequate consumption of mother’s milk shortly after birth may set the stage for this problem. Thereafter, weakness and hypoglycemia lead to chilling and dehydration. There is a drop in temperature and heart and breathing rates.
As the rectal temperature drops below 94°F (34.4°C), there is further depression of vital functions. Gradually, the crawling and righting reflexes are lost and the puppy lies on his side. Gagging and fluid in the nostrils may be noted. Later, poor circulation affects the brain, causing seizurelike spasms, accompanied by breathless periods lasting up to a minute. At this point, the condition is irreversible.
Early treatment is imperative to avoid death. Veterinary assistance is required.
Fading Puppies
These are puppies who are vigorous at birth but fail to gain weight and gradually lose vitality and the urge to feed. For want of a better term, the condition is called fading puppy syndrome. There is no agreement as to what causes puppies to fade. Some cases may result from immaturity, others from internal birth defects, environmental stresses, or maternal factors. The syndrome is reversible if the cause can be determined.