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‘they look normal when they are born and then they die!’
Taken from a talk given by Professor Danièlle Gunn-Moore from the University of Edinburgh at a recent PetPlan FAB Breeders symposium. Kitten deaths are of course a cause of distress for breeders, but the causes and the prevention methods are similar whether the situation is the breeding, home or rescue environment.
Sadly, it is inevitable that some kittens which are born will die and a low level of loss is to be expected. Generally pedigree cats have higher levels of kitten death than non-pedigrees or moggies. In one study, pedigree cats had an average kitten mortality of 34.5 % from birth to one year of age (range of 8 - 40 %), compared to 10 - 17 % in non-pedigree cats. These higher levels of mortality may reflect inbreeding within pedigree cats. However, it is difficult to get accurate figures for pet cats.
DEATH BEFORE WEANING
The percentage of kittens which die before weaning – this includes still births and deaths in the first 4 weeks of life is commonly 15 – 30 %. Stillbirths typically account for less than 10 % of all kittens born although this can vary considerably - from 6 – 22 % in pedigree cats.
Kitten deaths are highest in the first week of life (typically more than 90 % of all kitten deaths). After this mortality declines, only to rise again just after weaning. These losses usually result from non-infectious causes, while infectious disease cause more problems after weaning. This is because before weaning the kittens are relatively protected from infectious disease by maternally derived antibodies – this will be covered in the next issue of CatCare see graph). Kittens dying between birth and weaning are frequently called ‘fading kittens’.
Neonatal (newborn) kittens may die suddenly, or present as ‘poor doers’ and ‘fade’ within a few days. Unfortunately, the clinical signs of many of the diseases affecting newborn kittens are very similar and vague. While normal kittens tend to cuddle together and sleep contentedly between feeds, sick kittens tend to lie separately, are generally more restless, are not keen to suck, and cry frequently (if still strong enough to do so). See pics
Newborn kittens are vulnerable because mechanisms which regulate temperature control are poorly developed, they are at increased risk of dehydration and low blood sugar (hypoglycaemia), and the immune system is immature. Therefore, regardless of the initiating cause, these kittens can rapidly become cold or dehydrated, suffer from low blood sugar or lack of oxygen and die.
Hypothermia |
The rectal temperature of newborn kittens normally ranges from 35 – 37 oC in the first week, to 36 – 38 oC in the second and third weeks, and reaches normal adult levels of 38 – 39 oC by the fourth week of life. |
Kittens are predisposed to hypothermia because they cannot regulate their temperature. They
- Lack insulating fat and heat-generating brown fat
- Cannot restrict the blood flow to the extremities
- Cannot react to cold by shivering
- Have a large surface area to volume ratio that means that they can loose body heat quickly.
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| Hypothermia is particularly harmful as it can initiate a number of other problems. For example: a week-old kitten should have a temperature of 35 – 37 oC and a heart rate of 200 - 250 beats per minute. However, if its temperature falls to 30 oC, its heart rate will fall to 40 - 50 beats per minute. While this is initially a protective response, if sustained, it can lead to a decrease in respiratory rate, which may in turn lead to heart and lung failure. Also, a hypothermic kitten will not suckle effectively, its gastrointestinal motility will become depressed, and it will have an increased susceptibility to infection. It is therefore important to check the temperature of any potentially weak or ill kittens. However, if its rectal temperature is less than 34 oC the kitten is likely to die. |
Low blood sugar (hypoglycaemia) |
Newborn kittens are predisposed to problems associated with low blood sugar because
- They have high energy requirements (two to three times the adult equivalent)
- They have no energy reserves
- Their immature livers are inefficient at generating energy
- They have a reduced ability to digest nutrients and to absorb them from their gut.
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| Any kitten that is ill or stressed may develop hypoglycaemia. This may be seen as weakness, hypothermia, crying, difficult breathing, seizures, coma and, eventually, death. |
Dehydration |
There is a high risk of dehydration because
- Newborn kittens have a higher percentage of body water (82 %) than adults
- They lose more water through their immature kidneys, lungs and skin than adults
- Neonatal kitten maintenance fluid requirements are ~130-220 ml/kg/24h, compared to 50-65 ml/kg/24h for a mature cat
- Dehydration may result from inadequate consumption of milk, or excessive fluid losses (usually associated with overheating, excessively low humidity, or diarrhoea)
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Top: this litter of kittens is feeling cold and huddled together
Middle: Half an hour after turning the heat up they have spread out and look more relaxed.
Above: The kitten lying seperately in the box died some time later - it was found to have a gut problem and was unable to pass faeces.
Causes of ‘fading’ or sick kittens
Causes of 'fading kittens' |
Birth/queen-related factors |
(kitten lack of oxygen, trauma, hypothermia) |
Congenital abnormalities |
Low birth weight |
Inappropriate environment (temperature, humidity, hygiene, overcrowding, over-handling) |
Inappropriate nutrition |
Neonatal isoerythrolysis (NI) |
Infection (viral, bacterial, parasitic) |
Birth/queen-related factors
Kittens born after birthing difficulties (dystocia) have a significantly increased risk of death within the first few weeks of life. In fact, prolonged labour or such difficulties are probably the most significant causes of death during this time. This results from the effects of lack of oxygen (hypoxia) and/or trauma. Dystocia occurs in around 6 % of pregnancies (range 0 – 18 %). Studies have shown that cats with extremes of conformation (body form or shape), as in breeds such as the Siamese and Persians, experience more birth difficulties (7 – 10 %) than cats with normal conformation (generally less than 5 %). Lack of oxygen during birth can result in stillbirth, or the birth of weak, slow, kittens that fail to suck. These kittens usually die within the first week of life or, because they fail to ingest sufficient colostrum, are at increased risk of infectious disease.
Kitten mortality is usually highest in the first litter born to a particular queen and after her fifth litter. The high death rates in kittens from first-time queens probably relates to inexperience, trauma and cannibalism. Older queens tend to have smaller litters and tend to produce more kittens with congenital defects. The negative effect of extremes of litter size is seen as reduced survival of single kittens, and of kittens from litters of 7 or more. Kitten mortality also increases with increasing maternal obesity, and with other queen-related causes, including a lack of milk, mastitis, or maternal neglect.
Congenital abnormalities
Obvious physical defects may be seen in 10 – 20 % of stillborn kittens. However, this varies considerably from 1-10 % of kittens born to research cats (usually non-pedigree or moggie), to 1 - 31% of kittens born to pedigree cats. Congenital disorders are present from birth, and can affect any body system. They may result from genetic disorders or teratogenic factors (drugs, disease or other conditions which can cause physical defects).
Defects resulting from exposure to teratogenic substances may be seen in cats of any breed. For example, cleft palates may result from treatment with griseofulvin (for ringworm), corticosteroids, or excessive amounts of vitamin A; skeletal deformities may result from the administration of organophosphate anti-flea products. It has also been suggested that overheating (sleeping on a heated pad), in some pregnant cats, may result in an increased risk of skeletal deformity in their kittens. Severe defects usually result in stillbirth or early neonatal death. Milder disorders may result in fading kittens, or only become apparent later in life.
Because inbreeding increases the risk of genetic disease, congenital disorders are seen more frequently in pedigree cats. In addition, certain defects are seen more frequently in some breeds than others. (see FAB website for information on inherited defects).
Top: newborn Bengal kitten with anasarca - a deformity in which lots of fluid collects under the skin. The kitten was born dead.
Bottom: Two-week-old Bengal kitten with leg deformities. This self corrected with time - limb deformities like these can correct and it is worth giving them time to do so rather than euthanasing immediately.
Top: Spina bifida and deformity of the back legs in a stillborn kitten. The mother of the litter was inadvertently exposed to a poisonous substance.
Bottom: Ten-day-old moggie kitten with hydrocephalus (water on the brain). This was the only kitten in the litter and was apparently normal when born. It gradually became weaker and its head became deformed with the accumulation of fliud before it died.
Low birth weight
Underweight kittens are particularly susceptible to hypothermia, dehydration, respiratory failure and infection and have a significantly increased risk of neonatal death. This is because:
- They are physiologically immature compared to normal weight kittens
- They may be too weak to nurse adequately
- They lack insulating fat and thermogenic brown fat
- They have weak thoracic (chest) muscles and immature lung development.
Kittens may be born underweight because of maternal malnutrition or ill-health; congenital disease (disease present at birth); in utero infections; or any condition that results in poor placental blood supply.
The average birth weight for most breeds of cat and moggies is 100 g ± 10 g. However, it is normal for some breeds to have significantly smaller kittens (Oriental - average 80 g); while others have significantly larger kittens (Maine Coon) average 120 g). It is therefore very important to know what the average weight for kittens of a particular breed is when trying to decide whether or not a particular kitten is underweight. As a general guideline newborn kittens weighing less than 75 g are likely to have very high death rates. FAB questionnaire data
Inappropriate environment
Environmental factors, such as extremes of temperature and humidity, poor hygiene, overcrowding, or over-handling can all result in increased kitten mortality. Ideally the room where the kittens are kept should be well ventilated, draught-free, and maintained at a fairly constant 18 – 24 oC, 55-60 % humidity. This will allow the mother to be comfortable, and she can supply any additional heat required by the offspring.
Hand-rearing |
| Where kittens have to be hand-reared it is necessary to supply additional heating. Ideally the temperature in the box should be maintained at 29 – 32 oC, but the box should be large enough for the kittens to move away from the heat if they become too hot. The temperature is gradually reduced to 27 oC by 7 - 10 days and 22 oC by the end of the first month. Overcrowding will lead to increased infectious disease and disease resulting from competition at the mother’s nipples (which can in turn result in inadequate nutrition - see below). Over-handling will not only limit the kitten’s feeding time but, with nervous queens, may result in cannibalism of her kittens. For more information on hand rearing see FAB’s information sheet available on the website |
| Providing kittens with a suitable environmental temperature is essential. A kitten that has ceased to suck regularly will quickly become cold and hypoglycaemic. Since newborn kittens cannot shiver and are unable to control their own body temperature, hypothermia will result, and this will lead to a further reduction in activity and sucking. |
Inappropriate nutrition
Care should be taken to feed the queen an appropriate diet. Incorrect nutrition of the queen can affect the quality of the milk she produces. Generally, when the queen is healthy and producing adequate milk there should be no problems. Normal kittens should suck for the first time within 2 hours of birth - they can only adsorb colostrum in the first 16 - 24 hours of life.
Inadequate milk production may be associated with an inexperienced or overly nervous queen, old queens, sick or malnourished queens, dystocia, certain familial traits, systemic illness or mastitis. Inadequate milk uptake by the kitten can also result from anything causing kitten ill-heath or weakness, from competition and bullying by siblings, or any environmental factor that distracts or upsets the queen-kitten bond.
| * Weigh kittens regularly - at birth, daily for the first week, then at least twice weekly until after weaning |
| * A loss of less than 10 % may be expected in the first 24 hours |
| * There should be daily weight gain (around 10 – 15 g/day; 5 – 10 %) |
| * Kittens should double their birth weight by 1 - 2 weeks of age |
| * Weight gain should be steady and progressive |
| * Any weight loss (or lack of weight gain) should be investigated |
| * Kittens losing more than 10 % bodyweight are unlikely to survive. |
It is essential that kittens gain adequate nutrition as they have a greater risk of developing hypoglycaemia and dehydration (see boxes on page 00).
Since the kittens derive all of their food and water in the form of milk, when the supply is inadequate, supplemental feeding is needed. Where the kittens have been orphaned or the queen is unable to feed them they will need total replacement feeding.
Weaning should begin at 3 - 4 weeks of age. It is important to ensure that all of the kittens gain sufficient food at this time. In large litters competition at the food bowl can lead to weaker kittens being bullied and so eat less.
Neonatal isoerythrolysis
In certain cat breeds neonatal isoerythrolysis (NI) is a relatively common cause of fading kittens. It results from the destruction of a kitten’s erythrocytes (red blood cells) by its mother’s antibodies. The maternal antibodies enter the kittens via the colostrum.
The kittens are born healthy. However, after sucking, affected kittens may die suddenly or stop feeding, become  weak, and show haemoglobinuria (brown stained urine). These kittens may then develop jaundice, anaemia, tachypnoea (rapid breathing), and tachycardia (rapid heart beat). In severe cases this leads to collapse and then death. Surviving kittens may develop necrosis (death of tissue) at the tail-tip and other extremities, which may then slough (fall off) between 3 days and 2 weeks of age.
Table: Breed prevalence of feline blood types
100% Type A |
~80% Type A |
75-100% Type A |
60% Type A |
40% Type A |
Siamese |
Somali |
DSH/DLH |
Devon Rex |
British Short Hair (BSH) |
Burmese |
Abyssinian |
Persian |
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Tonkinese |
Birman |
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Oriental |
Maine Coon |
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Norwegian Forest Cat |
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NI occurs when a Type B queen gives birth to a Type A kitten. When the kitten sucks colostrum the maternal anti-A antibodies enter the kitten’s circulation and attack its erythrocytes, causing anaemia and jaundice. Since these antibodies occur naturally, the queen does not need to be sensitised by previous pregnancies or blood transfusions. The highest proportion of Type B cats are British Shorthairs, so NI is seen most frequently in this breed of cat.
Where NI is seen
- All sexually active cats should be blood-typed to prevent further inappropriate mating. (It is recommended that all British Shorthairs be blood-typed before breeding. This can be done using a simple in-house test card (Rapid Vet-H, dms laboratories).
- Ensure that Type B queens do not mate with Type A toms.
- Where an unknown mating has occurred, placental blood can be used to determine a kitten’s blood type. If the queen’s blood-type is known to be Type B, and a kitten is found to be a Type A, it can be prevented from sucking the queen, at least until it is more than 24 hours old. (While this procedure will prevent the occurrence of NI, the lack of colostrum will leave the kitten at risk of infectious disease).
- Kittens showing signs of NI, if more than 24 hours old, should be immediately removed from their mother to prevent further absorption of anti-A antibodies. In kittens, most colostral antibodies are absorbed by 12-24 hours old.
- Once removed, the kittens can either be fostered to a Type-A queen, or fed milk replaced formula for 24 hours. After this time it is generally safe for them to be returned to their dam.
- If the anaemia is severe a blood transfusion will need to be performed. However, despite removing the kittens as soon as clinical signs are noted, most affected kittens that die within their first week of life.
Read Part 2 of this article covers infectious causes of kitten death, click here for Part 2
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