I would say the same way you get human poo out of clothing. When the garment is white you can use bleach. When it’s coloured my first go would be baking soda followed by vinegar. Personally I’ve good experience with sunlight block soap. I make the garment first wet with piping hot water and rub the soap bar on the stain then scrub with a good hard scrubber. Rinse out with hot water and repeat.

Following this as I would love to know

Maybe visit a dry cleaner for some advice?