I use the guidelines listed on the bag or container of food but I have found the amounts to be on the high side for my boys.
As PTP mentioned, the kcal content and serving size guidelines will vary by formula.
You mentioned Purina but not which formula, so I'll use the one I feed for an example.
I feed my boys Purina Pro Plan Small Breed Savor. My smaller 3y old mini boy is around 12.5 lbs. He gets 1/4c at his first meal of the day, and another 1/4c at dinner.
At his weight, I'm feeding 1/2 of the recommended amount. He gets additional toppers on his two meals and treats thru the day, bringing him to something closer to the kcal amount recommended for the day.
Here's the serving size guidelines from the bag:
Feeding Guidelines
RECOMMENDED DAILY FEEDING AMOUNTS
Using a standard 8 oz/250 ml measuring cup which contains approximately 97 g of Pro Plan.
Calorie Content (fed)
4034 kcal/kg
393 kcal/cup
Weight | Feeding Amount | | |
---|
(lbs) | (kg) | (cups) | (grams) |
3 - 12 | 1.4 - 5.4 | 1/2 - 1 | 49 - 97 |
13 - 20 | 5.9 - 9.1 | 1 - 1-1/2 | 97 - 146 |
For comparison, here's one of their toy breed puppy formulas with feeding suggestions. You can see that the kcal content of one cup of puppy food is considerably higher than the adult formula.
Feeding Guidelines
RECOMMENDED DAILY FEEDING AMOUNTS
Using a standard 8 oz/250 ml measuring cup which contains approximately 117 g of Pro Plan.
CALORIE CONTENT
Metabolizable Energy (ME)
4457 kcal/kg
2022 kcal/lb
521 kcal/cup
Weight at Maturity | 1-1/2 - 3 months | 4 - 5 months | 6 - 8 months | 9 - 11 months | 1 - 2 years |
---|
(lbs) | (cups) | (cups) | (cups) | | |
0 - 3 | 1/2 | 2/3 | 1/2 | Feed as Adult | Feed as Adult |
4 - 6 | 1/2 | 2/3 - 3/4 | 1/2 - 3/4 | Feed as Adult | Feed as Adult |
7 - 9 | 1/2 - 2/3 | 3/4 - 7/8 | 3/4 - 7/8 | Feed as Adult | Feed as Adult |
10 - 12 | 2/3 | 7/8 - 1 | 7/8 - 1 | Feed as Adult | Feed as Adult |
| | | | | |
(kg) | (grams) | (grams) | (grams) | | |
0 - 1.4 | 59 | 79 | 59 | Feed as Adult | Feed as Adult |
1.8 - 2.7 | 59 | 79 - 88 | 59 - 88 | Feed as Adult | Feed as Adult |
3.2 - 4.1 | 59 - 79 | 88 - 102 | 88 - 102 | Feed as Adult | Feed as Adult |
4.5 - 5.4 | 79 | 102 - 117 | 102 - 117 | Feed as Adult | Feed as Adult |
Puppies start to nibble solid foods at 3 - 4 weeks of age. Keep moistened Pro Plan available at all times. Allow your puppy to eat at will until fully weaned (6 - 8 weeks). After weaning, Pro Plan can be fed moistened or dry. For best results, develop a regular feeding schedule such as three small meals a day for younger puppies. You can gradually reduce to one feeding in the morning and one in the evening as your puppy ages. The routine should not vary. As puppies near adulthood, their calorie needs may drop, and your puppy may begin leaving some food in the bowl. Don't misinterpret this as an indication of dislike for the food. Instead, begin offering less so your puppy doesn't overeat and stays in ideal body condition.
Nestlé Purina Research indicates that avoiding overfeeding of puppies may help their development. Maintaining ideal body condition is key to encouraging proper growth in all puppies, especially large breeds. The indicated amounts are only a guideline. If your puppy becomes overweight, a reduction of your puppy’s daily food intake may be appropriate. You may wish to consult your veterinarian about a weight control program.
Your older toy sounds as though she's exercising good poodle judgment in self regulating her intake. She may be picky as well, but 9lbs for a toy sounds healthy.
The 12 week old may just be going thru a growth spurt and will eat more for a while, if that's so.
What does your vet say?