Magnesium is a behind-the-scenes essential that keeps your chickens' nervous and muscular systems running properly. About 60% of a chicken's body magnesium resides in the bones, where it works alongside calcium and phosphorus to maintain skeletal strength — especially important for laying hens whose bones are constantly cycling calcium in and out for eggshell production. The remaining magnesium activates over 300 enzymes involved in energy metabolism, protein synthesis, and DNA repair.
Magnesium also helps regulate calcium movement in and out of cells, which means it indirectly supports eggshell quality even though calcium gets most of the credit. When magnesium is adequate, the shell gland operates more efficiently, and calcium crystals deposit in a more uniform, structurally sound pattern. Deficient hens may lay eggs with subtle shell texture problems that are easy to miss.
Heat stress is a significant magnesium concern for backyard flocks. Hens lose magnesium through increased panting and elevated respiration rates during hot weather, and this mineral loss contributes to the overall physiological strain that makes summer the hardest season for laying hens. Maintaining adequate magnesium through the diet helps birds cope with temperature extremes.
Laying hens need about 500 to 600 mg of magnesium per kilogram of feed. Most layer feeds and a varied diet with greens and grains provide this adequately. Pumpkin seeds and sunflower seeds are especially rich natural sources — a small treat handful goes a long way. If you notice unexplained watery droppings in otherwise healthy birds, check whether a magnesium-heavy supplement might be the culprit.
0.06% of daily nutrient intake
Magnesium makes up 0.06% of your chicken's total daily nutritional requirements by weight. That's a tiny amount — but it matters.
Reduced egg production, thin eggshells, muscle tremors or convulsions, reluctance to walk or perch, poor growth in pullets, sudden death in severe cases from cardiac arrest, increased sensitivity to heat stress, general decline in production before dramatic symptoms appear
Excess dietary magnesium causes watery droppings because it acts as an osmotic laxative (think Epsom salts, which are magnesium sulfate). Very high levels can reduce feed intake and interfere with calcium absorption, leading to thinner eggshells — the opposite of what you want.
| Life Stage | Size | Min | Max | Unit | Notes |
|---|---|---|---|---|---|
| Adult | — | 500 | 600 | mg/kg feed | Supports bone strength alongside calcium and phosphorus. Hens under heat stress lose magnesium through increased respiration. |
Source: NRC Poultry 1994; general veterinary consensus
Calcium and magnesium compete for absorption in the chicken's intestine and must be maintained in an appropriate ratio for both to function properly. The extremely high calcium levels in layer diets (3.5-4% of feed) can suppress magnesium absorption, and since magnesium is required for over 300 enzymatic reactions including the shell gland's calcification process, this creates a potential bottleneck. Magnesium also helps regulate calcium deposition, preventing it from ending up in soft tissues where it does not belong.
What this means: Layer feeds should include adequate magnesium (typically 0.15-0.25% of diet) to counterbalance the high calcium. If your hens show sudden death, tremors, or convulsions alongside adequate calcium and Vitamin D, magnesium deficiency may be the cause. Sunflower seeds and leafy greens in the treat rotation provide natural magnesium supplementation.
