A human newborn has more value than a newborn of any other species because of his POTENTIAL to develop greater traits and intelligence as he grows. A calf and a human newborn just can't be compared due to the enormous potential the human baby holds, in contrast to a calf who has no hope to become anything but a cow. So killing a human newborn, in my view, is much graver than killing, say, a kitten.
As a baseline, I value everyone simply for being human and existing. Even evil or vegetative people, I value.
However, there is a deeper realm of appreciation that I reach, and this I cannot define concretely. All I know is that when I encounter such an individual, whom I value, something "wakes up" in me and I suddenly feel like I am in communion with that person, regardless of the extent of our contact, and I feel deep respect for him, and I feel content to know that this person exists.
Contrariwise (to quote Tweedledee), when I encounter people whom I don't value in this sense, I remain flatlined, and no "extra" reaction is triggered within me.