Not surprisingly, lactation is the most nutritionally demanding part of reproduction. The queen is not only trying to meet her own needs, but also provide complete nutrition for a number of rapidly growing kittens. It is, understandably, one of the most important factors in raising healthy kittens.

The mammary glands are accessory reproductive organs, and respond to fluctuations in the reproductive hormones. These glands continue the function of the placenta, providing continuous nutrition in a form that the underdeveloped stomach and intestinal tract of the kittens can readily absorb.

Because the role of the mammary glands is so important, it helps to understand the complex anatomy involved. This is especially true if the queen is not producing milk.

The composition of a mammary gland is made up of three parts. The first is the simple gland. Imagine a water balloon, but with a thicker wall. The wall of the balloon is analogous to the cells that make and secret colostrum and milk into the lumen, or the reservoir of the gland. Each simple gland has a duct that empties directly out through the nipple.

The second part of the mammary gland composition is the complex gland. A complex gland is an organized group of simple glands. Queens will have anywhere from 4 to 8 simple glands in each complex gland. The complex gland is what we generally refer to as a mammary gland.

The third part of the mammary gland is the nipple or teat. Each nipple will have between 4 and 8 openings, each connected to a simple gland. An important consideration is that each opening represents a potential entry point for bacteria.

Typically, a queen has 8 mammary glands, with 4 on each side of the midline. Because of the location of the mammary glands, they don’t all share the same blood supply, and the glands will have different lymph drainage.

Successful lactation is a combination of both milk production and milk removal. Each one is critical for continued lactation through the desired weaning time. The milk is produced by the secretory cells of each simple gland, and stored in the lumen. Milk removal is passively done by the suckling of the kittens. Passive, because there is not an active procedure by the queen to empty out the glands. Milk letdown is the ejection of milk from the simple gland lumen into the ducts and to the nipples.

The stimulation of milk production is a collaboration of several factors. First is generation of mammary tissue and secretory cells in response to hormones. There are four hormones that influence milk production, estrogen, progesterone, prolactin and relaxin.

Estrogen triggers the development of all the sex organs and subsequently starts the estrous cycle each time. Part of the preparation for estrus and pregnancy is the development of the mammary glands.

Progesterone is primarily the hormone that maintains the pregnancy from breeding to delivery. One of the roles of progesterone is to prepare the mammary tissue for lactation.

Prolactin is a hormone that directly stimulates the mammary tissue to make milk. However, the success of the action of prolactin is dependent on estrogen levels.

Likewise, relaxin, a hormone that is only present during pregnancy, also relies on estrogen to be affective in stimulating the mammary tissue to function fully.

Other than these four hormones, the removal of milk from the gland lumens and ducts by suckling sends a chemical message to the brain that more milk is needed.

A hormone that is commonly recognized for its action in lactation is oxytocin. However, there is a major misconception with its use. Oxytocin acts to stimulate the contraction of the simple gland lumens, sending the stored milk into the ducts and nipples. It does not cause the glands to make milk, only to release that milk that has already been made. So if there has not been any milk made, oxytocin will have no benefit at all.

Colostrum is the first secretions of the mammary secretory cells at or near birth. It is rich in antibodies from the mother, which will help the kittens fight off viruses and bacterial invaders until their own immune systems can function fully. Antibodies, also known as immunoglobulins, are large molecules and normally they are too big for the cells lining the intestinal tract to absorb intact. However, for the first 24 hours after birth, the intestinal cells specifically assist these antibodies into the blood stream. After that time there is little if any intact absorption of the antibodies. Instead they would be broken down into composite parts, just like any other protein.

The degree of antibody absorption is dependent on three factors, the first being the amount of antibodies produced by the queen. Secondly, the amount of colostrum ingested by the neonate influences the amount absorbed. And lastly, the duration of the time during which the intestinal cells absorb the intact antibodies.

Cats can have problems associated with the antibodies in the colostrum. A condition called neonatal isoerythrolysis (NI) results when the kitten and the queen have different blood types. The mother naturally makes antibodies against blood types other than her own. These get secreted into the colostrum. When the kitten that has a different blood type than its mother ingests the colostrum and absorbs the antibodies, those antibodies then begin to attack the red blood cells it recognizes as foreign. This can be a fatal condition for the affected kittens.

Cats have types A, B and Ab blood. Some breeds have virtually 100% type A, and don’t experience neonatal isoerythrolysis. These breeds include Siamese, Burmese, Tonkinese and Oriental to name a few. Other breeds are known to have a fairly high prevalence of both A and B blood types, such as Devon Rex and British Short Hair.

When neonatal isoerythrolysis is occurring, the kittens will start to show signs within hours of first nursing. Sometimes the reaction is so strong that the kitten suddenly dies. In other less severe cases, the kitten will stop nursing during the first 3 days, exhibit a "failure to thrive" tendency, have dark brown-red urine and show a yellowing of skin around the nose and the pads of the feet. Some kittens will have relatively mild reactions and in this case will continue to nurse and thrive, but may have a mild anemia and show a necrosis, or dead tissue, at the tip of the tail.

Neonatal isoerythrolysis can be avoided. The best defense is to blood type the queen and tom prior to breeding. Breed only blood compatible animals (type B to type B). Appropriate management of the newborn kittens in potential NI situations can save the kittens. The first step is to remove the kittens from the dam before they nurse, for at least 24 hours. The kittens may be fostered to a queen with an appropriate blood type, or they can be hand-fed using commercial milk replacer. The kittens can be reunited with their mother after that time, and should do fine.

The composition of milk provides proteins, fats, carbohydrates, vitamins, and minerals. However, keep in mind that perhaps the most important nutrient provided by the milk is water. Newborns have a tremendous water turnover since they can’t concentrate their urine. On average, the milk will contain about 78% water. The neonates are very vulnerable to dehydration, so frequent nursing is necessary.

So, what’s the problem when the queen can’t make milk? The inability to make milk is called agalactia. True agalactia is very rare. More commonly the queen may be producing milk, but not enough. There are several reasons why this may occur.

There may be inadequate levels of any of the four hormones that stimulate mammary development and milk production. Or, the secretory cells in the simple glands may have inadequate or non-functional receptors, preventing the hormones from communicating with the cell. Likewise, there are genetic considerations as well, as some breeds and some family lines that aren’t prolific milk producers. Psychological factors can have a negative affect as well, seen in stressed animals, where the expenditure of energy to make milk is sacrificed in order for the animal to be able to "fight or flight".

Physiologically, inflammation of the uterus releases chemicals that negatively impact milk production. Likewise, inflammation of the mammary glands, mastitis, can impact one or more glands. If the kittens were delivered surgically, there may not have been adequate stimulation of the cervix by the passage of the kittens into the birth canal, which normally triggers the release of prolactin. In premature birth, the mammary glands may not be fully prepared to start lactation. And of course, if the queen has some systemic illness, her resources may be directed to fighting infection and healing instead of milk production.

It is imperative that the queen have access to as much fresh clean water as she wants. Her diet is equally important, for she needs a nutrient-dense, very palatable food, which is highly digestible. It must provide optimal levels of protein and fats, along with all the other essential nutrients. A queen that weighed 8 lbs prior to breeding, will produce up to 16 lbs of milk during a lactation period (roughly 7 to 8 weeks), which is the equivalent of 2 gallons.

Luckily, there are some options that may help a queen who is not lactating successfully. Drugs such as metoclopramide (Reglan) and domperidone can help. They work by different pathways, but each has shown effectiveness. Acupuncture has also been shown to be successful in many cases to stimulate milk production.

The main message is that at the first sign that the queen is not producing enough milk, seek veterinary care. The best chances of correcting the problem are dependent on how early the condition is caught, and the causative reasons discovered. By weighing the kittens daily, it is easier to see when they are not consuming enough milk.