Yes and No ......
There are some instances where "N' works and then not.
I think the "N" falls into play when the word is more
"trendy" or hip. PBNJ is commonly used Peanut Butter
and Jelly. PBandJ not so much use. RockNroll is cool
where as "Rock and Roll" is just OK.
From first hand knowledge I'll give you an exampe from
a couple of names I hold. One gets traffic and earns
parking rev. The other .....nothing.
RnB tube / com
RandB tube / com
Thats right .... the "RNB" is far more popular than "RandB"
In the case of your examples I think "Dogs and Cats" works
better than "DogsNCats".
NN