Brit Care Junior Large Breed Lamb & Rice

Hello, I have bought your product Brit Care Junior Large Breed Lamb & Rice for my 10-months old Bullmastiff male. Apparently, he is allergic to the food he has consumed since his arrival to Belgrade almost 7 months ago (it was Monge Superpremium Maxi Puppy with chicken), so after seeing his blood test, he suggested to change the food and buy a Lamb & Rice product. We have opted for Brit Care Junior Large Breed Lamb & Rice as this food seems to meet our needs. We started to give it today and hope for positive results. I have just one question about the daily dosage, unfortunately, people in the pet shop were not able to clarify things. Our dog is 10 months and weighs 50 kg (and he is not fat), the average weight of the adult dog is about 60 kg. According to the table you provide, at the moment he should eat 510 grams per day. With Monge he ate 750 grams per day, which is a big difference, all the more so, Monge has 4,120 kkal per kg while Brit 3,550 kkal per kg. Could you please clarify things a bit, perhaps the daily dosage is subject to adjustments? Or your food is different in the way how it is metabolized? My dog eats 3 times a day and when I gave him about 170 gr instead of regular 230, he looked hungry. Thank you in advance for your answer.