The first point is a non issue. If we just stop for a second and think about it, the calorie output of the animals has to be less than the calorie input. Otherwise they would generate energy out of thin air. The bigger thing is that they are also homeothermic animals, which means that majority of the input calories are used to regulate body heat and not to generate output calories (aka meat). From calorie persective, going through homeothermic animals is pure waste of energy.