A Menina e o Cavalo (1985)

The script plagiarized several elements of the great Woman, Woman (1979) of Jean Garrett. The whole cast is incredibly bad! The sex scenes are simulated and, of course, poorly made. Likewise, attempts at humor (like talking horses) are terrible. When someone laughs it is because of the ruin of production.

And just in case, just like that review says, all the scenes are obviously simulated,
without penetration shots and using a very obvious fake horse dong and fake cum.
Trust me, I’m an expert.