Please weigh once weekly throughout their whole life; daily if you know or suspect illness/problems with appetite.
http://www.guinealynx.info/weigh.html
Adult guinea pigs (over 15 months old) can weigh anything from 800g to 1800g and still be considered healthy; average is about 900-1300g. That is quite a big range and a long time to get there; hence charts are pretty useless. Any piggy with a bad background can still catch up in growth and weight until they are about 2 years old. With a good, balanced diet, your piggies will get there and realise their own individual ideal weight in their own good time. Please do not overfeed, as overweight can pose a risk in operations.
A good diet should consist of:
- unlimited good quality hay (up to 80% of the daily food intake). Vital to keep the guts balanced and the crucial back teeth ground down.
- about 50g/1 cup of mixed veg per piggy per day in as many servings as you like. Please include 1 high vitamin C veg or fresh herb daily, like a slice of pepper of any colour, a bit of broccoli (any part), a sprig of fresh coriander/cilantro, parsley, dill, fennel, basil or mint, a little bit of cabbage and vary between these. Feed fruit and tomatoes only 2-3 times a week in small quantities. Too much can cause sores to the mouth.
Here is a list of what they can eat:
http://www.theguineapigforum.co.uk/showthread.php?42-Vegetables-Shopping-List
- pellets (not muesli): unlimited until the weekly growth rate is slowing down between 4-6 months old, then very gradually reduced to the half or handful of pellets that a fully grown adult needs from 15 months onwards.
- fresh water without additives daily