The variable-flow feeder (1) of the invention is meant to be fitted in particular onto a milk bottle and comprises at the end of its nipple (2) a slit (3) with two arms (3a, 3b) subtending between them an angle, and is characterized in that the angle subtended by the two arms of the slit (3) is an obtuse angle .GAMMA. between 165.degree. and 95.degree. of which the vertex lies on the feeder axis, in that the lengths l.sub.1 and l.sub.2 (l.sub.1 >l.sub.2) of the slit arms form such a ratio l.sub.1 /l.sub.2 that it falls between a value of 1 and .delta., the value of .delta. increasing from 1 to 10, preferably from 1 to 4.5, when the angle .GAMMA. decreases from 165.degree. to 95.degree., said arms of the slit (3) being determined by cutting lines which do not remove material and issuing at their non-adjacent ends into a hole (4b, 4c) of small cross-section.