The major cause of reduced litter size were stillborn puppies, as 10.9% of the puppies were stillborn, reducing the average litter size with 0.8 puppies. This incidence of stillbirth is higher than reported in other studies. Bowden et al. [2] reported 7% stillborn puppies in a study of 541 litters of 111 breeds, and in a study of 413 Boxer litters 5.5% of the puppies were stillborn [4, 6]. The high incidence of stillbirth in our study may be due to more complete registrations of stillbirths, as the breeders prior to birth of the litter had signed a contract to record the information in a prospective study. Another factor was most probably that the average litter size was higher in our study (7.6) compared to these other studies: 5.7 [5] and 6.4 [4, 6], respectively. Our study showed a significant relationship between litter size and stillbirth; the average litter size was significantly higher in litters with stillborn puppies (8.9) compared to litters in which all puppies were born alive (6.9).
In 2/3 of the litters there were no stillborn puppies. Nearly 1/3 (31%) of all the stillborn puppies were found in 4 litters. Ten of these puppies were from one single litter, which is 12% of all the stillborn puppies in the study. This might indicate that in a larger study, like the studies of Bowden et al. [2] and Nielen et al. [4, 6], the rate of stillbirth will be lower, as a small number of litters with a catastrophic high rate of stillbirths will have less influence on the prevalence of stillbirth in the population.
It is reasonable to believe that most of the stillborn puppies in our study could have been saved with adequate veterinary assistance. In the litter where 10 out of 15 puppies were stillborn, the birth lasted for 40 hours. Despite the fact that most of the puppies were delivered by extraction and repeated injections of oxytocin, no caesarean section was performed. Another dam which received numerous injections of oxytocin, gave birth to 10 puppies, of which four were stillborn. The remaining two puppies, both dead, were removed by caesarean section 24 hours after the birth of the first puppy. Normally a birth should be completed within 12 hours. In some cases in large litters it might be acceptable that the birth continues up to 24 hours, on the assumption of sufficient uterine contractions and normal progress of the birth. Secondary inertia due to exhaustion is not uncommon in large litters. Injection of calsium borogluconate (14 mg Ca/ml, 1–3 ml/10 kg iv or 2–4 ml/10 kg sc) and glucose (50 mg/ml, 3–6 ml/10 kg iv or 5–10 ml/10 kg sc) may be given to support uterine contractions, if necessary supported by a low dose of oxytocin [11]. If the contractions still are poor and there are several unborn puppies, it would be advisable to perform a caesarean section. Very large litters may result in primary uterine intertia, due to overstretching of the uterus preventing uterine contractions [12]. When primary inertia is diagnosed in bitches with large litters, the treatment should be caesarean section. Primary uterine inertia was probably the reason why five puppies died in a litter of seven were caesarean section was performed too late to save the majority of the puppies.
The puppy loss during the first 3 weeks of life was 6.9% in our study. During the next 5 weeks another five puppies died or were euthanatized; the puppy loss from birth to 8 weeks was 7.5%. This is less than reported in other studies. In the study of Bowden et al. [2], the mortality of live born puppies from 0–3 weeks was 23.9% (not including stillbirth or puppies destroyed at birth due to deformities, weaklings, lain on by the bitch or euthanized due to wrong colour), and Hopper [3] found that 15% of the puppies that were born alive, died during the first week. In the Boxer study of van der Beek et al. [6] 12.4% of the live born puppies died before 7 weeks of age; another 3.9% were euthanatized due to white colour. One important reason for the lower preweaning mortality in our study might be the very low prevalence of infectious diseases. Herpes virus infections are rare in Norway, and there were no reports of herpes virus infections in this study. All the dams in the study had recent and valid vaccination against parvo, distemper and hepatitis viruses.
Very little or no milk production the first couple of days was reported in four litters. Six puppies from one litter died due to starvation. Two of the puppies were autopsied, and the breeder managed to save the last two puppies with milk supplement. In two other litters with very low milk production, four puppies with minimum weight gain and symptoms consistent with fading puppy syndrome, died within the first week. It is important to advice breeders to record the body weight daily the first week to ensure normal weight gain. It is not uncommon for a puppy to loose up to 5% of its body weight the first day, but it must gain weight during the next couple of days to survive. In this study the puppies that were alive at 8 weeks had an average daily weight gain of 8% the first three days and 12% during the next four days, compared to the birth weight. This is more weight gain than found in other studies [13], but is probably due to the fact that our population consists of large breeds that have a relatively low birth weight and more rapid growth compared to smaller breeds.
Colostrum is vital for passive transfer of immunity to the newborn puppy. Although dogs have an endotheliochorial placenta where endothelium of the uterine vessels is the only structure separating the maternal blood from the chorion, only small amounts (5–10%) of the total immunoglobulins provided by the dam are transferred to the foetus through placenta [14–16]. Colostrum represents the accumulated secretion of the mammary gland during the last third of pregnancy, and immunoglobulins secreted in colostrum are readily absorbed in the blood from the upper part of the small intestine few hours after birth. Intestinal absorption of immunoglobulins is minimal after 12 hours [17]. If the dam has poor or no milk production when the puppies are born or if the puppies are too weak to suckle, they should be given serum, preferably from the mother. The study of Bouchard et al. [17] showed that administration of 8–16 ml pooled serum sc at birth, or orally at birth and 12 hours post partum, provided similar effect as colostrum. If the puppies are too weak to suckle, they should receive an injection of 5% glucose sc to prevent hypoglycaemia [11].
A puppy that is apparently normal at birth but fails to survive beyond 2 weeks of age is often referred to as a fader. The aetiology for this fading puppy syndrome includes a whole range of causes, like poor mothering, inadequate nutrition, inadequate colostrum, trauma and congenital anomalies, low birth weight and infections [7, 18]. The clinical signs of many neonatal diseases are very similar and vague, like restlessness, crying, low body temperature, diarrhoea and breathing difficulties. In absence of a more specific diagnose the term fading puppy syndrome is often used. Because of the immature status of the newborn puppy, a sick neonate may rapidly become hypothermic, hypoglycaemic, dehydrated and hypoxic and then die – regardless of the initiating insult [8]. In our study, nine puppies died during the first 2 weeks of life due to the vague signs typical for the fading puppy syndrome, or maybe a better term would be "sick puppy syndrome". Four of these puppies had received inadequate colostrum due to the mothers' very poor milk production the first couple of days and had received no serum at birth to compensate for the missing colostrum.
Seven puppies, from 0–2 weeks of age were killed due to trauma caused by carelessness of the mother. The breeds in this study are large breeds, and the weight of the newborn puppy in these breeds is about 1% of adult weight. Even a small incautiousness of the mother can result in lethal trauma to the puppy. To prevent this, the dam should be looked after by the breeder when she is nursing and feeding her puppies until the puppies are 2 weeks old.
