guinea pig poo change

Question
Hello there. I have 2 female guinea pigs, both about a year and a half old. Over the past few days, I have noticed a big change in their pool. Its usually plentiful, harder, and brown in color. It is now, very mushy, very dark in color, almost looking black, and not nearly as plentiful as usual. It happening to both my girls. I had been feeding them Mazuri Timothy based guinea pig diet (pellets). I recently switched to Oxbow adult guinea pig diet. I also feed them veggies, but have always done that. Do you think itcould be the pellet change? They also get unlimited hay and water, of coarse. Thank you.

Answer
It could be the diet change.  You don't mention what veggies you're feeding, but you might want to stop that for a few days and see if the color and consistency returns. Dark stools can mean a variety of things but is usually the result of diet.

Go back to your original Mazuri pellets. They are a top rated pellet for guinea pigs and there really shouldn't be any reason to change unless it is one of cost, which I understand. After a couple of days without the veggies, and back on the Mazuri feed, you can see if the stool is going to return to normal. That shouldn't take more than 48 hours.

Start the veggies, one at a time. That way if the dark stools return you will know which veggies they are reacting to. In other words it's a matter of testing them to rule out each thing one at a time.

Although they may not be particularly happy about losing their veggies for a few days, they will indeed get over it.  

Please let me know how this works for you, and if you have any other questions please feel free to ask.