Colostrum - Friend or Foe?

By DMV PhD. Urs Giger & DMV Margaret Casal, University of Pennsylvania

Colostrum is a pale, milky fluid secreted by the mammary glands at the beginning of lactation. In mammals, thus far studied, colostrum is known to contain larger amounts of specific proteins than milk. The most important of these are antibodies, also known as immunoglobulins. They are formed by the mother´s immune system to protect against a variety of infectious agents such as vira and bacteria. During the end of pregnancy and throughout lactation these antibodies are transportated via blood to the mammary glands, where they are actively secreted into the colostrum and subsequent milk. Upon nursing, the neonate absorbs these colostral immunoglobulins (Ig) intact from the gut into the blood during the first few hours to days of life. Because the ingested immunoglobulins originate from the mother, they are also called maternal antibodies. The protection of the neonate against various infectious agents through the maternal antibodies is known as passive immunity versus active immunity in which the animal develops its own protective antibodies. However under certain circumstances, the maternal antibodies may also attact and destroy the newborns red blood cells, thereby causing fatal incompatability reactions known as hemolysis of the newborn or neonatal isoerythrolysis (NI). Thus colostrum may be valuable by protecting against infectious diseases or be detrimental by causing neonatal losses.
Although little is known about feline colostrum presently, it is generally accepted that colostrum is important for the protection of newborn kittens against various infectious diseases until their own active immune system fully develops, at which time they can be safely and effectively vaccinated. On the other hand, one of the major causes of fading kitten syndrome is certain maternal antibodies. These contrasting issues have raised questions about the beneficial effects and risks of colostrum such as:

  • How long can colostral antibodies be absorbed by newborn kittens? How much does the colostrum differ from milk? Can colostrum-deprived kittens develop normally and survive? Is there a safe and effective substitute for colostrum? Which kittens are at risk of developing NI?
  • How can NI be avoided?

Over the past few years we have undertaken studies, supported in part by the Winn Feline Foundation, to answer some of these questions and to provide breeders and veterinarians with guidelines on ways to safely raise kittens.

Feline colostral antibodies

The development of mammary glands can be noticed after about 50 days of pregnancy and colostrum is produced shortly before and after birth. In order to characterize the maternal antibodies, we collected a few drops of colostrum and milk by gently expressing various mammaries from several queens shortly before until a few weeks after birth. The fat which is present in similar concentrations in colostrum and milk was removed and the antibodies were measured in the defatted fluid using a sensitive assay. Colostrum from all queens contained large amounts of two types of immunoglobulins, IgA and IgG, both known to provide protection against a variety of infections. However, the quality of these colostral antibodies appeared to vary between queens and from lactation to lactation of a particular queen. IgM, a third type of antibody was present in colostrum of some , but not all queens. Thus the amount and type of feline colostral antibodies appear to be similar to those in other species.

Feline colostrum versus milk

Typically colostrum changes into milk after the first nursings or during the first few days of lactation. In other species, colostrum is known to be much richer in antibodies than milk. Therefore, it is important that these newborn animals recieve colostrum in order to be protected against infectious diseases. To our surprise, however, colostrum and milk from queens appeared to contain very similar amounts of antibodies. We did not find an apprechiable decline in colostral/milk antibody concentrations over the first two weeks of lactation. This information may be most usefull when dealing with newborn kitens whose queen has died; is unable to produce milk; is unable to nurse or has colostrum that might be harmful to the kittens (see NI). In such situations, these kittens may initially be foster-nursed by another queen anytime during her lactation. Even days to weeks after delivery her milk will apparently contain sufficient amounts of antibodies to protect newborn kittens. Furthermore, the daily ingested antibodies may continously contribute to the local immunity of the gastrointestinal tract.

Uptake of maternal antibodies via colostrum and passive immunity

In contrast to humans but similar to most other species, no maternal antibodies are passed through the placenta to the fetal cat. Thus newborn kittens do not have maternal antibodies at birth and are therefore unprotected against a variety od diseases.. The transfer of maternal antibodies from the queen to a kitten occurs exclusively via colostrum or milk. Within minutes or hours after birth kittens find the queens mammaries andstart nursing and with each nursing a kitten may ingest several mililiters of colostrum or milk. Ingested maternal antibodies pass unharmed theough the stomach and are readily absorbed in the gut. These absorbed antibodies circulate in the blood and provide the kitten with passive immunity i.e. protection against various infections. In order to determine the degree and length of of maternal antibody absorbation, we repeatedly collected small bloodsamples from three groups of kittens. One group was allowed to suckle regularly, the second group was removed from the queen at birth for a few hours, and the the third group was given foreign immunoglobulin orally at different times after birth. However, the time interval during which antibodies could be absorbed was very brief, lasting less than 16 hours in each kiten studied. Thereafter, antibodies ingested by colostrum or milk were either destroyed in the stomach and gut or could not be absorbed by the intestine, which is similar to the situation in adult cats. Maximal maternal antibody concentration in the blood of kittens were reached during the first few hours to the end of the first day of life. The amount of colostral antibodies absorbed varied between litters as well as kittens of the same litter. Factors that apparently influenced the degree of absorbtion included antibody production by the queen, the amount of colostrum ingested and the duration of intestinal absorbtion. It is presently impossible to predict how many antibodies are absorbed by a kitten. In fact, a kitten who has gained more weight than any of its littermates during the first day of life may have absorbed the largest quantity or no antibodies at all.

The kitten´s protection during the first few weeks

After birth the concentration of maternal antibodies slowly declines over the first few days and weeks, and the passive immunity of a kitten fades. On the other hand, the kitten´s own immune system slowly develops during the first twelve weeks of life and antibodies are subsequently produced. In fact, some kittens studied were already capable of producing a specific type of antibody (IgM) at birth, which may be protective against certain diseases.
However, in catteries with frequent upper respiratory infections (herpes and calici viruses), panleukopenia (parvovirus) and other infectious diseases, colostrum deprived kittens are more likely to develop serious signs of disease than kittens with maternal protection. In these situations, it is most important to assure the absorbtion of maternal antibodies. For orphaned neonates, milk from another lactating queen may provide adequate protection if absorbed during the first few hours of life (<16h). If no lactating queen is available, sreum given either orally or subcutaneously during the first few hours of live may provide a comparable protection, but more research is needed to establish practical and effective guidelines. Kittens deprived of colostrum or lacking maternal antibodies may be safely vaccinated earlier than six weeks.
As demonstrated, colostrum has many beneficial effects. However, certain antibodies present in the colostrum may be determined by causing neonatal isoerythrolysis (NI). Fortunately, this devastating blood incompatability reaction can be avoided by blood typing queen and tom, breeding only with blood compatible males and/or appropriate management of newborn kittens.

Feline bloodtypes and anti-A antibodies

Blood types or blood groups are genetic markers on the surface of the red blood cells that may differ between individuals. Thus far only one blood group system has been recognized in cats. According to the AB blood group system, cats can have 3 different bloodtypes: A, B or AB. (Since there are no cats with bloodtype 0, the feline AB blood group system is different than the human AB0 blood type system) Type A is by far the most frequent bloodtype in domestic shorthair and longhair as well as pedigree cats. The frequency of type A and type B varies between geographic locations and breeds. For instance all Siamese and related breeds (Tonkinese, Burmese) have type A blood. The highest proportion of type B blood is seen in British Shorthairs and Exotics as well as Cornish Rex and Devon Rex cats. With respect to the inheritance of these bloodgroups, type A is dominant over type B, and type AB occurs very rarely in various breeds and is inherited separately. Thus, a mating between two type B cats always produce type B offspring.Depending on whether the type A cat is carrying the B gene or not, matings between type A or type A and type B cats may result in all type A offspring or type A and type B offspring.
Cats develop antibodies against the bloodtype they do not posess. In particular, all type B cats produce very strong antibodies against type A red blood cells. They are known as naturally occuring anti-A isoantibodies. In contrast type A cats have only weak anti-B isoantibodies, and type Ab obviously have none. It is the strong anti-A isoantibodies of the bloodtype B queen that is important when breeding cats and raising kittens, as they are responsible of fatal NI of type A (or AB) kittens. Bloodtyping can be performed by submitting a purple top (EDTA-containing) tube with at least a few drops of blood via first class or express mail to our laboratory (Dr. Urs Giger, Bloodtyping, Dept. of Clinical Studies, University of Pennsylvania, 3900 Delancey Street, Philadelphia, PA 19104-6010) or many other veterinary labs.

Feline Neonatal Isoerythrolysis

As indicated above, all type B queens produce large quantities of anti-A isoantibodies. These anti-A antibodies are along with other antibodies secreted by the mammary glands into colostrum or milk. When colostrum or milk containing anti-A antibodies is absorbed by a newborn kitten, an acute incompatability reaction known as NI can occur in kittens with type A or type AB, as these maternal antibodies will attack the type A or AB red bloodcells of these kittens. Type B kittens born to type B queens will not be harmed by these anti-A antibodies as they are the same bloodtype. Based upon the bloodtype frequency in the various breeds and the fact that only type A (or AB) kittens born to a type B queen are at risk for NI, the risk of producing a litter with NI when randomly mating cats of a particular breed can be calculated. It is considered to be zero in Siamese and related breeds and as high as 1 in 4 in British Shorthair andDevon Rex.
Because no maternal antibodies cross the placenta in cats, type A or AB kittens produced by type B queens are born healthy. However these kittens may get ill upon ingesting colostrum or milk containing anti-A antibodies. They may suddenly die during the first day of life without showing any other sign. They may develop marked pigmenturial (brown urine) and jaundice. This discoloration is caused by the breakdown of red bloodcells. The dark orange-brown urine, the hallmark of finding NI, may be readily detected by stimulating the newborn to urinate with a moist cotton ball. These kittens will fail to thrive, are reluctant to nurse and may die during the first week of life. Kittens who develop pigmenturia rarely survive. Other kittens at risk may not show any obvious signs or only lose the tip of their tail at 1-2 weeks of age. The observed variability in colostrum and maternal antibody absorbtion may explain the large differences from subclinical to fatal NI in susceptible kittens, although we are presently unable to predict which type A-kittens born to a type B queen will develop lifethreatening clinical signs.

Prevention of NI

Fortunately there are several ways to prevent NI. By typing all breeding cats and safely mating type B queens only to type B toms, no cases of NI will ever occur. However, suitable type B toms may not be readily available, or a type A tom may be preferred for other reasons. In these situations, as long as one accepts the risk of losing kittens and extra work to manage the newborns, a breeder may still safely raise these kittens. Although we initially recommended removal of type A kittens for the first day up to 3 days of life from the type B queen, our recent studies have considerably shortened this time period, thereby circumbenting the problem of the queen ceasing to lactate. As staed above, the maximal length of absorbtion of maternal antibodies from ingested colostrum or milk is less than 16 hours. Thus, newborns at risk to have to be removed at birth from their queen with bloodtype B for only 16 hours. During this brief period, trhe kittens may be fosternursed by a lactating type A queen who generally will accept thekittens. Since this has several advantages - requiring the least amount of work by the breeder and assuring maternal protection of the newborn through ingestion of colostral antibodies against infectious diseases - many breeders have elected to breed a type A queen before a type B queen.They have achieved excellent results as long as they were present at birth to immediately remove the kittens. Alternatively kittens may be nursed with a commercial milk replacer (see manufacturers guidelines) for the first 16 hours. This short delay in nursing appears not to affect lactation by the queen negatively. All kittens should be bloodtyped. In fact at birth cord blood from the placenta may be used to type kittens. A simple typing procedure may soon become available, thereby allowing immediate detection of type A or AB kittens at risk for NI.
In conclusion colostrum can either be of great value or be detrimental to a newborn kitten. Although feline colostrum and milk appear to provide excellent maternal protection of the neonate against infection, colostrum-deprived kittens have a chance to survive normally. Type A or AB kittens at risk for NI should be fosternursed for 16 hours by a type A queen or milk replacer, thereby avoiding NI reactions.