Biological experimentation on domestic guinea pigs has been carried out since the 17th century. The animals were used so frequently as model organisms in the 19th and 20th centuries that the epithet guinea pig came into use to describe a human test subject.
Hay racks Hay racks arent safe at all for guinea pigs because it restricts hay and piggies need unlimited access to hay 24/7 as it makes it 80-85% of their diet and it helps grind down their teeth as they never stop growing.

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Guinea pigs thrive on highquality hay that supports digestion, dental health, and overall wellbeing. This guide highlights top hay products commonly recommended for small animals, with a focus on timothy hay and alfalfa hay that suit different life stages and dietary needs.

What I have found now is that they are doing some poos in the tray but others (and wee) just outside (probably as they don't want to soil the hay I put in the tray). I was wondering if a hay bag might be the answer but would welcome thoughts - and recommendations of a safe one to buy.

Furthermore, visual representations like the one above help us fully grasp the concept of Some People Use Hay Balls With Guinea Pigs.
Hay bags for guinea pigs are a must-have accessory for ensuring your pet has constant access to fresh hay. Discover various hay bag variants available!