Lysine is an essential amino acid, meaning guinea pigs cannot produce it and must obtain it entirely from food. It is critical for growth, tissue repair, collagen production, and calcium absorption. Lysine also plays a role in immune function and in the production of carnitine, which helps convert fatty acids into energy.
For guinea pigs, lysine is often the first limiting amino acid in a hay-based diet — meaning it is the amino acid most likely to be in short supply relative to the body's needs. Timothy hay provides some lysine, but its levels are lower than in legume hays like alfalfa. This is one reason alfalfa hay is recommended for growing guinea pigs (under 6 months) and pregnant sows — it is richer in lysine and other amino acids needed for rapid growth.
Quality guinea pig pellets are formulated to provide adequate lysine. For adult guinea pigs on a timothy hay diet, the combination of hay, pellets, and varied vegetables typically meets lysine needs.
Guinea pigs need approximately 0.6 to 0.8% lysine in their diet by dry matter. Timothy hay provides about 0.3 to 0.4%, so quality pellets and varied greens supplement the rest. Growing pigs and pregnant sows benefit from alfalfa hay's higher lysine content.
0.74% of daily nutrient intake
Lysine makes up 0.74% of your guinea pig's total daily nutritional requirements by weight. That's a tiny amount — but it matters.
Poor growth (especially in young guinea pigs), muscle wasting, rough coat, impaired immunity, slow wound healing, and reproductive problems.
Excess lysine from food sources is metabolized and excreted without issue. Not a concern on any normal guinea pig diet.
| Life Stage | Size | Min | Max | Unit | Notes |
|---|---|---|---|---|---|
| Adult | — | 0.6 | 0.8 | % of diet | Percentage of diet dry matter. Often the first limiting amino acid in timothy hay. Quality pellets compensate. |
| Juvenile | — | 0.8 | 1 | % of diet | Growing guinea pigs have higher lysine needs. Alfalfa hay and alfalfa-based pellets support this. |
Source: NRC 1995, general veterinary consensus
