If the ע is pronounced correctly there should not be a problem telling the difference. I'm sure you said somewhere that you are studying Biblical Hebrew, Ingeborg. So you know the traditional phonetic transcription of these sounds. In real life, not many people are going to talk to pigs, unless it's a pet with a name. If the meaning is not clear from the context, even a modern Hebrew speaker will be able to emphasise the correct sound. It's just like the indefinite article in English, normally pronounced as a shewa, but if it's important to emhasise the indefiniteness of something, then you will say "a" like the letter of the alphabet.
That's very clever, so have a lingot. For those who want to know more about this, here's a link: https://www.thetorah.com/article/why-rome-is-likened-to-a-boar
I belive the English animal sound is oink, oink, but I am not good enough in the English language so I have to interpret his body-language if I want to understand what he is trying to say to me....I guess there aren't many pigs in Israel, but does it exist a hebrew word for the sounds the pigs express?