Yes, guinea pigs can eat clover but you need to make sure you slowly introduce this flower to their diet and only give them a few leaves at a time as to not give them an upset stomach. It is possible some piggies will not enjoy it either so take you time with new foods.
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It is important though that you introduce clovers gradually to their diet and not all at once.
This means only a few leaves at a time at first and then slowly a little more.
Also only feed clovers to your guinea pig if they like them. Some piggies may not enjoy them.
It is also good to note that variety is important for their diet and that this food should not be a staple of their diet. It can just be something in the rotation of foods they eat.
Make sure that there are no pesticides or any other treatments on the clovers before you feed them to your piggy as well.
Lastly make sure that you do not feed too many clovers to your guinea pig as too much of anything is a bad thing as it does contain a lot of calcium.
You may give your guinea pig an upset stomach if you give them too many clovers so limit the intake.