QUOTE(jotaro12 @ Dec 18 2009, 09:05 AM)
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Actually my ideal kitty weight is around 7-8kg

I want him to build up his weight with muscles rather than fat

Since he's active so won't be a problem i guess. Did see a pet tv show last week about a Norwegian cat with 12kgs of weight !! His owners are trying hard to loose his weight. Now he's 10kg and will continue to do his exercise
Felix is still around 3.5kgs. Vet didn't say he's skinny, only I'm concerned about his appetite these days. Regarding the supplement, I don't know the name but it's from the same company which I got my hairball meds. Company name is Vetoquinol Prolab with a lion head logo.
(update: Can't remember the exact image but came out 2 names after searching google, 1 is Felovite II and the other one Nutri-Cal)Bingo.. the supplement you talking about is Hi-Vite Drops (Vitamin supplement with liver and iron - fortified with antioxidants)
right? orange box with lion logo on it...
try that once on my cat that has bad appetite.. like super skinny, and yes it helps.
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how bad is your cat appetite anyway? since you feeding orijen, you need to remember that orijen is 100% meat... you cann expect your cat to eat the same amount of royal canin with the orijen... they eat less Super premium cat food like orijen... more on premium... so alot with low food.
orijen 100% meat, they easily feel full with small amount.. since it is high fat and protein. eating less doesnt mean no appetite and not eating.. they eat less but gain lots of nutrition.
with orijen, normally you can see differences after 3-4 month feeding it.. seriously i do comparison between my cat eating orijen and iams.. yes.. orijen give alot of different more than the one eating iams.
3.5kg is a standard body size.. depends on the body length. you can see the body structure if your cat is short hair.. i have a short hair male cat weight 4kg - very long body length... when i neuter him.. and now he's 6-7kg but still with the same look.. which im happy

look tough and like a real fighter

so your cat i think your cat length and weight looks nice.. vet also say not skinny. potentially your cat will grow like the one i tell u above..