I get a little to attached to virtual pets (don't ask me why), especially Minecraft because I like to self- role play as I play Minecraft. Anyway, I especially like to feed them,even if I'm not trying to breed or raise their health. I find I feel loved if I get the heart particle. I've been trying to feed my dog steak (and yes, it's cooked), but he won't eat unless his health is down, and I hate to punch him just to make him eat. And when he does eat, I get no particle effect. I've tried both in creative and survival, and both have this problem. Is this just a bug? Or am I doing something wrong?
One reason that there might not be the particle effects is that you're feeding them soon after being fed earlier. The time is 5 minutes. Wait 5 minutes, and you can probably get the particles again once you attempt to feed them again.
Quote from the Minecraft wiki:
They will not be able to enter love mode again for 5 minutes, and they may only breed once per item given.
Link to the wiki page: Mincraft Wiki: Breeding