Not sure about the big cat feedings but I think probably they aren't notified. With the Gorillas at Port Lympne, they do advertise twice daily scatter feeds, whereas at Howletts they are fed from the roofs of the enclosures several times a day, at least once during the afternoon when visitors are about, but times aren't advertised or exact to my knowledge.
The only thing they advertise at Howletts is the 'Talks' but usually they feed the animals or give them some kind of enrichment whilst the public are about for the talk, I was at Howletts yesterday and watched the Clouded Leopard talk, and there was two Ladies one talking to the public and one feeding bits of meat to 'Tai Wada' the Clouded Leopard so the public could see him. So if you want to see the Animals being fed or given enrichments then usually the talks are the best place to go.