Collie food will need to contain animal proteins and healthy carbs, vitamins and minerals, and omega fatty acids--nutrients every dog needs to maintain its health in the long term. This means the best "Lassie" dog food is premium dry kibble, as it has balanced portions of the above-listed ingredients.
Adult Collies, depending on their size, age, and activity levels, will need about three cups of dry food per day, divided into two meals. Collie puppy food portions are a bit smaller: again depending on age, about two cups per day, divided into three meals (not two) until six months of age.
For more info on feeding a Collie puppy through adulthood, here's a handy Collie feeding chart:Dog AgeDog WeightFood TypeAmountFrequency2 Months10 lbsDry (Puppy formula)0.33 cups3 times/day3 Months20 lbsDry0.5 cups3 times/day6 Months40 lbsDry0.75 cups3 times/day9 Months50 lbsDry* (Puppy/Adult)1.25 cups2 times/day12 Months60 lbsDry (Adult formula)1.5 cups2 times/day
*--Around this time, transition to adult food by mixing in adult formula with the puppy formula, in slowly increasing amounts with each meal, for one week.
Try if possible to stick to the above-listed portions. Though not especially prone to obesity, if these dogs are constantly overfed (and under-exercised) they certainly can become overweight--and a fat Collie dog will have numerous health problems and a potentially shortened lifespan. You can help control your Collie's weight by having consistent feeding and exercise schedules, by not feeding the dog table scraps (and easy on the Lassie dog treats!), and by not leaving food in the dog' bowl all the time.
If you're worried your Collie is overweight, try this simple test: run a hand along the dog's side, and if you can't feel any ribs, it's diet time--which means less food and more exercise!