The Apple version of Farming Simulator 17 was, at its beginnings, subject to really crippling graphics problems during the game: black artefacts on the outlines of 3D models, kinds of large blinking squares.
If the bug had been corrected during the versions, and completely absent since version 1.4, it is back with the update of this beginning of the week, the 1.5.1. Not all configurations are affected by its display faults. To read here and there on the various forums, it seems that Macs equipped with a retina screen are particularly affected by this phenomenon. And bingo, I have a MacBook Pro Retina mid-2015 (AMD Radeon R9 M370X 2 GB + Intel Core i7 + 16 GB + 512 GB SSD), the racehorse displays these famous black squares.
The solution
My config is able to run the game with all the options pushed to the max. I had to grope each setting independently before finding the one to modify to correct the shooting: Anticrenelage / Antialiasing (multisampling). Either deactivate it, or push it all the way to 8X (if your machine allows it) but if you put it in 2X mode, it's done!