You may have noticed that there is dog milk replacer, cat milk replacer, cow milk replacer... Why all the different kinds? The constituents of milk vary widely from species to species. The metabolism and proper function of the digestive tract of newborn animals depends on them receiving the proper amounts and ratios of the components that make up their normal milk.

The major constituents of milk include:

  • Fat, the principle energy component 

  • Carbohydrates, mostly in the form of the sugar lactose 

  • Protein

  • Minerals and vitamins

  • Water

The amount and ratio of these constituents varies widely between species.

Species Fat
Ratio of
to Fat
(milk sugar)

Bear, polar

31 10.2 0.3 0.5 57


10.9 11.1 1 3.4 75


3.9 3.3 0.8 5.0 87


19.7 10.4 0.5 2.6 66


8.3 9.5 1.1 3.7 79

Guinea Pig

3.9 8.1 2.1 3 84


1.6 2.7 1.7 6.1 89


12.2 10.4 0.8 1.8 74

Seal, grey

53.2 11.2 0.2 2.6 32

Some milk, like that of the polar bear and seal, have extremely high levels of fat. When you think about where these animals live and their environment, that is understandable. The newborns will need a lot of fat to keep them warm. Some milk, like that of the horse and cow are over 85% water. If newborns of these species were fed a more concentrated milk, they would develop serious digestive tract problems.

If you have a nursing pet, and it needs supplemental milk, find a commercial product designed specifically for your species. If no commercial products are available, you will need to make a home formula that closely approximates the milk of its mother. Components may include commercial cat milk replacer, cow or goat milk, condensed milk, yoghurt, egg yolks, vegetable oil, Karo syrup, salt, and vitamin supplements. Talk to your veterinarian, wildlife rehabilitator, or other expert before making any formula on your own. Knowing how much to feed and how often is also very important.

Note: Many 'orphaned' wild animals are not orphaned; their mothers are close by and watching. Leave young wild animals alone, and call the humane society, wildlife rehabilitator, or government natural resources office if you feel the young are truly orphaned. These people have the most experience and will provide the best care for these animals if they are actually orphaned. In addition, remember that keeping wild animals, even orphans, without being a licensed wildlife rehabilitator, is against the law in many places.

Holly Nash, DVM, MS
Veterinary Services Department, Drs. Foster & Smith, Inc. 
Web Site


For eons, mother’s milk has proven to be the best food for newborns. Studies in several species have documented the mechanisms that keep milk high in nutritional value regardless of the condition of the dam.

These studies verify that a lactating bitch will produce a sufficient quantity of nutritious milk to support her puppies even if her condition deteriorates. For conscientious dog breeders, the challenge is to provide nutrition for the dam that will allow her to not only feed her puppies, but also to maintain her own condition.

It is normal for a bitch to lose some bodyweight during lactation but, ideally, the amount lost should not exceed 10% of her original weight. It is much easier to attain this goal if the bitch is in good condition prior to whelping which usually reflects the fact that she was in good condition at mating.

Excellent nutrition, though crucial, is not the only step that breeders can take to insure a healthy dam after her puppies are whelped. Clean, dry facilities are important. Daily exercise and fresh air can make the nursing process more pleasant for the dam, too. Daily examination of the dog’s mammary glands allows early detection of infection in the breasts allowing prompt treatment.
Of course, a plentiful supply of clean water is very important to the well-being of the dam. Water consumed by the bitch is important to the puppies as well because water turnover is very high in the newborn puppy. This function of nursing is often overlooked by breeders. A consistent fluid intake by the puppy is required to maintain blood volume and this hydration function of milk is as important as the nutritional role.


One of the fascinating features of the nursing process is the ability of milk to change over the lactation. For example, the energy content of dog milk increases steadily for the first 40 days of nursing then decreases by day 50, coinciding with the puppies’ ability to eat solid food. This allows an early start on shrinkage of mammary tissue to help the bitch end her milk production. 

Fat content in the milk varies over the lactation period as well. Early in lactation, the fat level is about 2.4%. By the middle of the nursing period, the fat level increases to about 5% then decreases to about 2.6% near weaning.

Calcium is high in milk during the entire nursing period but continues to increase as weaning nears. Magnesium, iron, and zinc all vary over the lactation stage.

It is important to note that the dam’s nutritional level must be very high in order to allow this normal variation of nutrients and to provide optimal nutrition for the puppies. A specific example is the so-called “toxic milk” syndrome, which can affect puppies between 3 and 14 days of age. This condition may be caused by uterine infection and/or mammary infection, but some cases respond to zinc supplements suggesting that the disorder may be due, in part, to inadequate zinc intake. This example illustrates the necessity of a high nutritional plane to supply the various nutrients required by the nursing bitch.

Failure to consume colostrum during the critical period when the intestine is open to intact protein
absorption seriously compromises the immune status of the neonatal puppy. This occurs either through the bitch’s inability to produce colostrum or the puppies’ inability to nurse properly. Suitable corrective action requires the manual collection of colostrum from another bitch or a frozen source, then provision to the puppy via stomach tube.

Although much less desirable, colostrum from another species (eg, bovine) may be used. The antibodies provided by cattle colostrum may not be protective for the puppy, but other non-specific defences may be utilized (lysosyme, lactoferrin, and oligosaccharides). These nutrients protect the puppy against bacteria by destroying the pathogen or protecting the puppies intestine against bacterial toxins.


Most dog breeders are unaware of the large quantity of milk produced by lactating bitches. For example, milk intake of Beagle puppies is about 5.5 ounces per day each. With an average litter of pups, a Beagle bitch will need to produce about one quart of milk per day! Larger breeds will be required to produce substantially more milk each day. Milk production decreases as puppies begin eating solid food, but milk alone can support normal growth in puppies up to four weeks of age.
Regardless, the large amounts of healthy milk required by most litters necessitates a very high level of nutrition for a successful nursing process. This fact, plus the reality that puppies are totally dependent on their mother’s milk for nutrition and hydration, makes the production of large quantities of high-quality milk even more poignant.





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