Layer mash is a loose, ground feed formulated specifically for hens that are actively laying eggs. It looks like a coarse, crumbly mixture of grains, minerals, and vitamins, with most particles ranging from 1 to 3 millimeters in size. What sets it apart from other chicken feeds is its high calcium content, typically 3% to 5% of the total diet, which hens need to produce strong eggshells day after day.
What’s in Layer Mash
The bulk of layer mash is coarse-ground corn or other grains, which supply energy. Mixed in are finer particles containing amino acids, phosphorus, vitamins, and trace minerals. The result is a blend of large and small particles rather than a uniform texture. A well-made layer mash has roughly 55% to 85% of its particles in that 1 to 3 mm range, giving it a gritty, meal-like consistency that hens can pick through.
Protein content varies depending on the breed and how much feed a hen eats per day. White-egg layers generally need diets with around 15% to 19% protein, while brown-egg layers, which tend to be larger birds, require 15% to 22.5% protein. Calcium requirements follow a similar pattern: white-egg breeds need roughly 2.75% to 4.12% calcium, and brown-egg breeds need 3.33% to 5%. Available phosphorus sits much lower, around 0.21% to 0.38%, but plays a critical supporting role in bone health.
Why Calcium Levels Are So High
An eggshell is almost entirely calcium carbonate, and hens form a new one roughly every 25 hours. Most of that shell calcification happens overnight, when the hen isn’t eating and has no fresh calcium coming in from her diet. To bridge this gap, hens pull 20% to 40% of the calcium they need directly from their bones, specifically from a special type called medullary bone that acts as a calcium reserve. During the day, when the hen is eating again, that bone re-mineralizes and restocks its calcium supply.
This cycle of borrowing and replenishing works well in younger hens, but calcium absorption from the gut decreases with age. Older hens rely more heavily on bone-derived calcium, which raises the risk of fractures over time. Layer mash addresses this by including coarse limestone particles that stay in the gizzard and slowly dissolve overnight, providing a trickle of calcium even during the dark hours when hens aren’t actively feeding. The hen’s body reduces the pH in her intestines to help dissolve these limestone particles when demand is highest.
Mash vs. Pellets vs. Crumbles
Layer feed comes in three physical forms, and “mash” refers specifically to the loose, unprocessed version. Pellets are the same ingredients compressed into small cylinders, while crumbles are pellets broken back into smaller pieces. Each has trade-offs.
- Mash is the simplest and often the least expensive form. Hens can pick through it selectively, which some keepers see as a benefit (it encourages natural foraging behavior) and others see as a drawback (hens may leave behind fine particles that contain essential vitamins and minerals). Mash can also be messier, and waterfowl in particular struggle with it because the dry, loose texture is hard for them to swallow without water.
- Pellets are easier for birds to eat quickly and produce less waste, since every bite contains the full nutrient profile. Hens can’t pick out their favorite bits and leave the rest.
- Crumbles offer the uniform nutrition of pellets in a smaller size, making them popular for younger birds transitioning to adult feed.
For most backyard flocks, the choice between these forms comes down to preference and budget. Mash works perfectly well as long as you use feeders that minimize spillage.
When to Start Feeding Layer Mash
Chicks and young pullets should not eat layer mash. The high calcium content that supports eggshell production can damage the kidneys of birds that aren’t yet laying. Chicks start on starter feed, move to grower feed, and then transition to layer mash around 18 weeks of age, which is when most breeds begin laying their first eggs.
Plan to have your layer feed ready by week 16 so you can make a gradual switch. Mix increasing amounts of layer mash into the grower feed over about a week, and by the time eggs start appearing, your hens should be fully transitioned. If some birds in your flock start laying earlier or later than others, the arrival of the first egg is your cue to begin the switch for the whole group.
Fermenting Layer Mash
Some backyard chicken keepers ferment their layer mash before feeding it, and the practice has real nutritional benefits. Fermentation is straightforward: you soak the mash in non-chlorinated water in a clean bucket, leaving room for expansion, and let naturally occurring lactic acid bacteria do their work in an oxygen-free environment. Within a few days the pH drops from around 6.5 to about 4.2. You’ll see bubbles and smell a sour, yogurt-like odor.
The lower pH creates an environment where harmful bacteria like Salmonella and E. coli can’t thrive, while beneficial bacteria multiply. Chickens eating fermented feed tend to have healthier gut flora, stronger immune responses, and lower rates of illness. The fermentation process also breaks down compounds in grains that normally block nutrient absorption, unlocking more phosphorus (important for bones) and making proteins more digestible. Many keepers report their birds eat less fermented feed by weight while maintaining the same production, since more of each bite is actually absorbed.
To do it safely, use only filtered or dechlorinated water (chlorine kills the beneficial bacteria you’re trying to grow), feed only what your flock will finish in a single day, and remove any uneaten portions promptly. Store your fermenting container in a cool, dark spot, and refrigerate extra prepared feed for no more than one to two days.