A sachet (11) for packaging animal semen, comprising two thermoplastics material films delimiting a pocket (12) along a closed path of generally rectangular shape defining two shorter sides and two longer sides when the sachet is empty, wherein one of said shorter sides has an interruption extended by a filler conduit (14) and defining a filler area (15) in said thermoplastics material films and the other of said shorter sides has an interruption extended by a drainer conduit and defining a drainer area (17) in said thermoplastics material films, characterized in that said drainer conduit (16) has two different diameters (D1 and D2), of which the smaller diameter (D1) is at the end communicating with the interior of said sachet.