Are Chickens Lactose Intolerant?

Are Chickens Lactose Intolerant?

One of the many sources of nutrients my chickens enjoy in their varied diet is milk from my Nubian dairy goats. Sometimes they get it fresh and warm, straight from the morning milking. Other times I stir in fines — those bits of leaves and seeds that accumulate at the bottom of the goats’ hay manger — and let it ferment overnight. By the next morning, it has naturally turned into a yogurt-like or soft cheese consistency with a divinely herbal odor. As tempting as it smells, I’ve never tasted it, but my chickens mob me when they see their milk bucket coming.

On the other hand, I hear repeatedly that chickens are lactose intolerant. Indeed, old-time poultry keepers fed milk to their growing birds to deliberately cause diarrhea to flush out the organisms that cause coccidiosis. So what’s the deal?

Lactose and Lactase

Lactose, otherwise known as milk sugar, is a type of sugar found only in dairy products. Lactose is a disaccharide, “di” meaning two and “saccharide” being another word for sugar. In order for lactose to be digested, it must be broken down into its two constituent simple sugars, or monosaccharides — glucose and galactose — both of which are readily digestible.

Baby mammals, including humans, are born with the enzyme lactase, which breaks down the lactose in mother’s milk so it can be digested as glucose and galactose. As some mammals mature and move on to other foods besides milk, their bodies produce fewer lactase enzymes and they become less able to digest milk. The result is a genetically determined condition known as lactase deficiency or lactose intolerance. One of the signs of lactose intolerance is diarrhea.

Chickens, of course, are not mammals. Although they are omnivorous, in their natural environment they would not normally encounter mammalian milk or products derived from it. Oddly, however, their bodies still produce some lactase. They can, therefore, tolerate small amounts of lactose.

Some dairy products are naturally low in lactose. Cottage cheese, for instance, is particularly low in lactose. And some of the lactose in a live-culture dairy product such as yogurt gets predigested by the culturing microbes. At the opposite extreme, dried dairy products like milk powder and buttermilk powder are high in lactose. The accompanying table indicates the approximate percentage of lactose in various dairy products.

Avoid the temptation to feed your chickens Lactaid or any similar product to overcome their lactase deficiency. These products are simply a lactase substitute; they work by breaking down lactose into glucose and galactose. A large amount of galactose is toxic to chickens. Giving your chickens Lactaid so you can increase a number of dairy products you feed them is decidedly a bad idea. On the other hand, if you drink lactose-free milk and want to share it with your chickens, that’s okay. A little galactose can actually be beneficial.

How Much Is Enough?

Researchers at the University of Illinois found that feeding galactose to broilers at the rate of 10 percent or more of the total diet resulted in increased deaths. But galactose fed at the rate of 2 to 4 percent improved the broilers’ growth rate. (“Impact of galactose, lactose, and Grobiotic-B70 on growth performance and energy utilization when fed to broiler chicks,” Poultry Science, October 2003)

The table below tells us fluid milk is approximately 5 percent lactose. Figuring half of that is galactose, and assuming it all gets digested, a broiler that ate or drank nothing else but milk would have a diet consisting of 2.5 percent galactose — well within the safe and beneficial range. However, a diet consisting solely of milk will not provide your chickens with complete nutrition, and anything you add to improve the nutritional profile reduces the overall percentage of lactose and therefore galactose. So feeding fluid milk to chickens is a pretty safe bet.

The Maine Organic Farmers and Gardeners Association thinks so. One of their published fact sheets says, “Milk is a good source of protein and can be fed instead of water for half the day, with water available the other half of the day.” (“Feeding Whole Grains to Chickens,” MOFGA Fact Sheet #13)

Milk and other dairy products also may be used to give chickens extra energy when the weather is cold and days are short — a time when hens may not eat enough to both maintain body heat and continue laying well.

Milk is 87 percent water. The remainder is loaded with protein, carbohydrate, fat, vitamins, and minerals. One of milk’s minerals is calcium, which is needed by chickens of all ages.

One of milk’s vitamins is riboflavin (vitamin B2), which is needed by eggs intended for hatching. Breeder hens that are penned up and fed unsupplemented lay ration may produce chicks with curled toe paralysis, a condition in which the toes curve inward, causing the affected bird to step on its own feet. While some such chicks survive, others starve because they can’t get to feed and water. Curled-toe paralysis is a good indication that the breeder-flock diet is deficient in riboflavin. Along with tender greens, milk, whey, and other dairy products are sources of riboflavin.

Milk, when fermented into live-culture yogurt, makes a good probiotic for chickens. The small intestine of a healthy chicken (and also a healthy human) is populated with a number of beneficial microbes that aid digestion and also produce antibacterial compounds and enzymes that stimulate the immune system. If for any reason these beneficial microbes get out of balance, disease-causing microbes can take over and cause an enteric (intestinal) disease.

A chick naturally acquires some of these microbes through the egg and gains more from the henhouse environment. Beneficial microbes are also present in certain foods, including grains and cultured milk. Chickens that eat a varied diet or are free to peck out some of their sustenance from their environment typically do not need a probiotic. Chicks raised in a brooder, however, acquire beneficial gut flora more slowly than chicks raised under a hen. A little live-culture yogurt will enhance their immunity by giving them an early dose of gut microbes similar to those that will eventually colonize their intestines naturally. Antibiotics and other antimicrobials kill disease-causing and beneficial microbes alike.

Any chicken that has been treated with an antibiotic or subjected to extreme stress may enjoy an immunity boost from a live-culture dairy product.

Milk Flush

Since a chicken would not encounter lactose as part of its natural diet, when undigested lactose reaches its intestines, the chicken’s body wants to flush it out. Accordingly, the intestines draw fluids from the bloodstream, and the influx of moisture results in diarrhea. Old-time poultry keepers took advantage of this fact to control coccidiosis by treating infected chicks with a milk flush.

The procedure was to add milk powder to the regular ration at the rate of 25 percent (one pound of milk powder per three pounds of ration) for up to seven days. Plenty of water was also made available to prevent dehydration, since treated chicks drank three times more than usual during the flush.

Of course, the loose droppings made a mess of the litter, which had to be cleaned out and replaced daily. Or if the chicks were on pasture, they had to be moved to new ground daily. Frequently removing the loose droppings, or moving the chicks away from the mess, kept the birds from ingesting expelled coccidia, thus preventing reinfection until the disease ran its course.

Some modern chicken keepers believe that milk, offered occasionally or continuously, will prevent coccidiosis. Not so. Feeding an excessive amount of lactose to induce mild diarrhea is a method of controlling an existing outbreak of coccidiosis.

Treating chickens with a milk flush is not without dangers. The bacteria Escherichia coli, which cause a group of infections collectively known as colibacillosis, consider lactose to be prime food. E. coli are normally present in small numbers in every chicken’s gut, but during times of stress or illness the bacteria can proliferate out of control. Feeding milk to chickens at such times also feeds the E. coli, giving them extra nutrients, in the form of lactose, that allows them to multiply in even greater numbers.

Cultured milk, on the other hand, is low in lactose and helps prevent enteric diseases through the concept of competitive exclusion — meaning that when a chicken’s gut is populated with a healthy dose of good microbes, the good guys will work hard to keep out the bad guys. Note, however, that bacteria and protozoa do not inhabit the same ecological niche in a chicken’s gut.

Therefore, competitive exclusion resulting from the beneficial bacteria in live-culture yogurt does not directly apply to coccidia (which are protozoa). However, boosting your chickens’ immunity with cultured milk will help keep them generally healthy and better able to resist diseases of all kinds.

Chickens and Milk




Dairy Product — Lactose

Milk Powder, Nonfat — 51%

Buttermilk Powder — 48%

Milk Powder, Whole — 38%

Milk, Fluid — 5%

Whey (liquid) — 5%

Yogurt, Kefir — 4%

Sour Cream — 4%

Buttermilk — 4%

Cottage Cheese (2%) — 3.6%

Cottage Cheese (1%) — 2.7%

Cottage Cheese — 0.4%


Gail Damerow is the author of The Chicken Health Handbook, The Chicken Encyclopedia, Your Chickens, The Backyard Homestead Guide to Raising Farm Animals, Hatching & Brooding Your Own Chicks, and the completely updated and revised classic Storey’s Guide to Raising Chickens, 3rd edition.

Originally published in the February/March 2014 issue of Backyard Poultry magazine.

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