This posture is detailed here, which is page 80 in the book Yoga A New Life Style by Muni Kishan Lal and published by B. Jain Publishers Pvt. Ltd.
In the modern world and context of mass factory farming, animal abuse, human population overshoot, environmental degradation, and increased nutritional knowledge, we can invite possible other interpretations of this posture (as well as connect to the past signifiance and tradition of it). For instance, other than for human use, why else may a cow be milked? A cow or her calf may be served by being milked for instance if a calf has sadly died or if a calf is very ill and needs milk to be taken to him or her.