Magnesium supports bone structure (about 60% of your rabbit's magnesium is stored in bones), nerve signaling, muscle relaxation after contraction, and hundreds of enzymatic reactions throughout the body. It works alongside calcium and phosphorus in bone metabolism and helps prevent muscle cramps and spasms. Rabbits on a good hay-based diet generally receive adequate magnesium without supplementation. Magnesium also plays a role in calming the nervous system, which matters for these naturally alert and sometimes stress-prone animals.
A generous serving of parsley (about 15g) provides roughly 8mg of magnesium — your adult rabbit needs approximately 30 to 40mg of magnesium per day (about 0.03 to 0.04% of the diet), which is comfortably met by a normal intake of timothy hay supplemented with dark leafy greens.
0.05% of daily nutrient intake
Magnesium makes up 0.05% of your domestic rabbit's total daily nutritional requirements by weight. That's a tiny amount — but it matters.
Muscle tremors or spasms, poor growth, weakness, hyperexcitability or nervousness, and in severe cases, convulsions. Magnesium deficiency is rare in rabbits eating sufficient hay and leafy greens.
Excess magnesium from food sources is very rare, as the kidneys efficiently excrete surplus amounts. Extreme excess from supplements could theoretically cause diarrhea or lethargy, but this is not a practical concern from a whole-food diet.
| Life Stage | Size | Min | Max | Unit | Notes |
|---|---|---|---|---|---|
| Adult | — | 30 | 40 | mg | Adequate magnesium from hay and greens. About 0.03-0.04% of diet dry matter. |
Source: NRC 1977, general veterinary consensus
Calcium and magnesium work together in bone formation and muscle function, but excess calcium can interfere with magnesium absorption. Given that rabbits absorb all dietary calcium, maintaining appropriate levels of both minerals matters.
What this means: A varied diet of timothy hay and rotated greens naturally provides a healthy calcium-to-magnesium balance. Avoid consistently feeding only high-calcium greens, which could shift this ratio unfavorably.
