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Nutritional Comparison Guide: Day old chicks, Mice, Rats

There is little doubt that varying a carnivorous reptile pet’s diet pays dividends in overall health and longevity. Some food items are easier to acquire and maintain than others, and there are differences in cost and convenience. Whenever possible a consideration of nutritional factors should be the keeper’s first consideration. Many animal species can provide food for reptiles, but there are three that are most commonly used. This guide will describe the pros and cons of each of these food items.

Day-old chicks (DOC): 

Excellent Source of Protein

It is hard to match the affordability and convenience of day old chicks, but there are some considerations to be aware of. Adult reptiles with reduced protein and calcium needs will thrive on a diet of DOC that is occasionally supplemented with another type of prey.  But very young, growing pets will need more calcium than chicks alone can offer.

Without a doubt, however, DOC are superior to rodents when it comes to high protein content. Keepers who are concerned about fat content can go to the trouble of removing the yolk sac from frozen and thawed chicks, but obviously this step cannot be taken when feeding live chicks.

Deficient in Calcium

Day old chicks are super convenient, but are deficient in calcium and other nutrients needed to keep a growing reptile healthy. A diet of only DOCs for years can lead to disease and even heart attacks. DOCs only have a little over half the nutritive value of an equal weight of older chickens or other foods. It is the yolk that causes problems due to the high levels of phosphorous that interfere with the calcium levels in the bird. This can be solved by raising some of the live chicks to one week old, at which time the yolk sac with have been completely absorbed by the growing chick’s body. 

Freeze Week Old Chicks

A very good feeding strategy would be to buy a large lot of day old chickens, freeze 1/2 immediately and brood the other half for 7 days and then freeze or feed out.  Chicks being brooded as late feeders will need an excellent diet that includes plenty of calcium and vitamin D. Miracle Care Vionate is a good supplement for this purpose. It is advisable to leave the skin and feathers on them and wrap them individually in freezer bags to prevent freezer burn, which can affect nutrition.  Chicks should be fed out before they have been frozen for 4 months. 

As can be seen from the table below, chicks are an excellent source of protein. The calcium problem can be solved by either alternating food items, such as the occasional rat or mouse, or offering older chickens that have been fed a reptile friendly diet.

If feeding day old chicks exclusively, and the keeper does not know the maternal diet (fed to the laying hen), then it is wise to assume that D3 supplementation for the reptile will be needed on a weekly basis. Hypovitaminosis D3 (too little) causes problems with calcium metabolism, and leads to rickets. This is exacerbated by low calcium, high phosphorus-containing diets, such as embodied in DOC. A typical sufferer would be a young growing reptile, kept indoors with no ultraviolet light supplementation and fed on a low-calcium diet of only day chicks. Without supplements or varying the diet, this can lead to metabolic bone disease.

As the chart shows, day old chicks are incredibly high in Vitamin E. Most reptiles tolerate this nutrient readily and hypervitaminosis is seldom an issue. However, if the pet being fed is having trouble with blood clotting factors, it would be prudent to introduce rodent items with more frequency. DOC can be low in other nutrients, such as iron and zinc. This is another reason to vary the diet occasionally. 

Given the very reasonable cost of frozen chicks (around $1.00 each for bulk order), this a very nutritious food, giving good value for money. Live chicks that may be needed to raise a certain number of them to greater maturity for reasons of improved nutrition tend to run approximately 2.5 times more than the frozen variety. 

One word of caution about feeding an item with so much protein. Many, many keepers have complained that feeding chicks results in strong smells and very runny feces from their pets. A few have stated that they have not noted a difference, but most attest to a poop problem.  Some keepers use chicks in order to clean their snakes out, and then go back to rodents. Others report that after a few consecutive feedings of chicks, that the poop firms up and stops smelling as their animal’s gut adjusts to the new food. It seems likely that switching back and forth two often between chicks and rodents can cause issues. 

Mice

Mice are typically the most expensive food available to reptile keeper’s in terms of their cost to weight ratio. 

Mice are great options for snakes that are more active such as the “slim” species such as corn snakes, Dekay Brown Snake, rat snakes, and king snakes. Due to their fat content, mice provide more immediate fuel that snakes with quick acting metabolisms can utilize and put to good use.

Not enough calcium

Independent analysis has shown that frozen pinkie mice have a 0.79:1 calcium:phosphorus (Ca:P) ratio while adult mice have a 1.4:1 Ca:P ratio. Some people say that if you feed pinkie mice just after they have fed on milk that the calcium level increases. This appears to be logical; however, there are no published data to support this. As with DOC, it is advisable to supplement a diet of pinkies with a commercial calcium product.

A lot of Fat

Compared to chicks and rats, young mice take the cake for calories.  Pinkies can be approximately 30% fat, slimming down to 18% as adults. For reptiles, this much fat is not a bad thing in moderation. Fats provide high concentrations of energy. They also supply the reptile or amphibian with essential fatty acids (EFAs), which are required for cellular integrity and as the building blocks for certain hormones such as prostaglandins.  Fats also provide a carrier mechanism for the absorption of fat-soluble vitamins such as vitamins A, D, E and K.

The primary EFA for reptiles is linoleic acid, as it is for mammals, with the absolute dietary requirement of this fatty acid being 1% of the diet. If the diet becomes deficient in this EFA, a rapid decline in cellular integrity occurs. This is manifested clinically by the skin becoming flaky, inelastic, and prone to recurrent infections and even fluid loss through the skin.  So to improve skin health and integrity, pinkie mice are a great choice.  Fuzzies can be provided for larger snakes that need a boost.

The problem of overconsumption of fats in pet reptiles who are not exercising regularly is obesity, which can lead to a number of problems, high amongst which is fatty degenerative change in the liver (hepatic lipidosis), which can lead to liver failure.  It is for this reason that feeding mice to carnivorous reptiles should be considered like offering candy, something to be done only occasionally and certainly not as a steady diet.

Rats

Less Fat More Protein than Mice

The most significant difference in nutritional value between rats and mice is that young mice contain more fat than young rats and are slightly lower in protein value per gram weight. Other than those two important distinctions, both rodent types are comparable in terms of vitamins and minerals.

Rats are better for larger snakes

Keep in mind that different species of snake will also fare better on different types of feeders. The general consensus amongst reptile enthusiasts is that heftier bodied snakes such as pythons and boas benefit greatly from consuming rats on a regular basis. 

Because rats are higher in protein, this tends to mean that larger snakes with slower metabolisms (i.e. pythons and boas) can digest them more efficiently. They will therefore receive more nutrients from any given meal and will ultimately require fewer feeding sessions.

Calcium in Rats

Neonatal rats have less calcium than adult rats, just as one would expect. Snake owners with large snakes are better off feeding adult rats monthly, rather than rat pups weekly. The exception would be a snake or lizard that is a very picky eater, needs fattening, or is extremely active, in which case the occasional pair of mice would be a nice change. 

Cost of Rats

Cost can be a consideration with this food item. Large frozen rats cost approximately $4.00 each when purchased in small lots, such as bags of 10. A live rat from a pet store will cost in excess of $10 in most parts of the country. 

Although that may seem like a lot, consider that a neonatal rat pup weighs 7 grams, while a pinkie weighs only 2 g. A large standard breed rat weighs 140 grams, while an adult mouse will be lucky to tip the scales at 30 grams (extra large breed).  So it takes more than 4 large mice to equal the food weight of one large rat.  Frozen jumbo mice tend to run around $1.55 each when purchased in bulk. You can see that over time, rats are the better value as well as the best nutritional choice.

Comparison

At the end of the day, all of these food choices have something to offer carnivorous reptile keepers. Choice will depend upon the reptile size and species, and sometime dietary preferences. Nutritionally, keepers of medium to large snakes should feed older chicks and adult rats. Keepers with slender, active species should feed DOC and mice of various sizes. Keepers with overly thin and unthrifty reptiles that they are trying to fatten should have more mice than DOC for until improvement is achieved, and then the ratio should reverse. 

A diet of older chicks and rats is ideal for boas and constrictors. Some keepers have reported advanced growth rates for snakes raised primarily on chicks and chickens. All of these keepers do provide supplements along with the whole food item. 

One advantage of live chicks is that they can be used as live food without concern for the reptile pet’s safety. There is very little evidence that frozen chicks are less nutritious, however, improper freezing over time does impair the nutritive value of the food item, something that the keeper doesn’t have to worry about when the food is still alive. Some keepers with picky eaters may prefer to feed live chicks, despite the increased cost, as a way of stimulating the strike response  in their finicky pet. There is also some data that indicates that chicks are more palatable to many snake species than rodents are.

When keeping chicks to raise for older feed items, the keeper has the option of essentially gut-loading the birds, much like one would do for feeder crickets or other insects. A diet specifically designed for the needs of the reptile can be offered to the chicks. This ensures that any pets with special needs or medical conditions get the nutrients they need without the guess work of which nutrients the chicks come equipped with. For instance, DOC can vary widely in their iron percentages, so a custom feed can compensate for any short falls.

For nutrition x cost comparison, depending on the quantities ordered, the ranking for best food item would be DOC, then rats, then mice. This will vary by the animal’s size, health and species, but with that in mind, and with careful shopping, DOC appear to be the best choice for most reptile owners with carnivorous mouths to feed.