Diet can changing hay/pellets result in weight loss?

[tenar]

I have three (fostered) guineapig boys who are now nearly 5 months old. They have been gaining weight nicely, but recently one of them didn't gain weight in a week. I got worried, so have been paying closer attention to their weight (weighing every couple of days) and it seems that they have all either not gained weight or lost a little weight over the last two weeks.

I'm (possibly strangely) less worried now that it's all of them rather than just one, so looking for an overall possible cause. One of the things I changed is their diet: I got a delivery of baby guineapig pellets (Oxbow), so started mixing those in with their other Pellets (Vetafarm Cavy Origins - not sure that's available outside Australia, but it's recommended by the rescue, along with Oxbow, so it's what I had to start with).

I also got a bag of different hay: they had been on an Oaten hay, but I got a bag of Timothy/Rye hay, having read that they usually like Timothy hay best (but yikes it is expensive, which is why I haven't gotten it for them before.

So I'm wondering could they have been losing weight because I changed the hay and the pellets? I thought pretty much any of the "recommended" hays were OK and nutritionally much the same. The guineapigs are still having about 50% of the previous type of pellet, and they've had that hay before (I figure that mixing the types of hay up isn't a terrible idea in general). So it doesn't seem so likely to me. But it is what I changed just before they started to lose weight/ not gain weight.

I have now switched back to giving them some Oaten hay along with the Timothy/rye one. They do seem to prefer the oaten hay. I'm waiting to see if their weight comes back on. I'm hoping that Oaten hay in general is going to be good, because I've just bought them a whole bale of it which is sitting in my storeroom (I can't normally access feedstores readily, but we were out of the city for a couple of days).

Has anyone else changed hay and seen their cavy's weight drop?

 

[bpatters]

I'd assume that the slowdown in weight gain is due to the change in diet. But I wouldn't worry a whole lot about it unless they're actually losing significant amounts of weight. I'd be willing to bet that they'll start gaining again even on the new diet.

 

[Soecara]

Once I had to change hay types simply due to a shortage of the type i usually feed meaning it simply wasn't available at the time. I usually feed oaten hay, but had to change to wheaten hay (the only kinds of hay available in my area are oaten, wheaten, lucerne/alfalfa, or very small bags of poor quality imported timothy).

Most of my guinea pigs tolerated the change, they weren't happy about it but they did eat the wheaten hay. Two of my sows lost a little weight about 30-50g, the exception was one boar who went on a hunger strike and ended up dropping 150g. I ended up supplementing him with fresh grass and corn husks until i could get my hands on some oaten hay (i ended up having to drive 1 hour away to pick it up, so a 2 hour round trip).

Personally I would go back to feeding your guinea pigs a fresh local hay. My reasoning for this is the timothy hay you will find here in Australia is almost certainly imported as it doesn't grow well here, hence part of the reason for the very high price. At they very least this means the hay is likely old, and it likely would have been irradiated to be able to pass quarantine.