If the figure does represent a cattle species, the clearly carved collar, garland and necklace could help explain its function. Sacrificial animals in village India are often garlanded and decorated similarly today.
Ancient Indus Valley civilization seals
Mackay writes that most of the bosses on the backs of seals had the same size and shape. The perforation always runs in the direction of the animal's body, to help keep the seal upright when worn around the neck.
The boss is centered on the back and
Mackay continues (p. 377 in Marshall 1931):
"The boss was then carefully rounded off after the groove that always runs across its centre had been roughly made by a V-shaped cut.
This seal from Mohenjo-daro measures 29 mm (1.14) inches on each side and is made of fired steatite. Steatite is an easily carved soft stone that becomes hard after firing.
In the rubble were found a number of inscribed pieces, including this intaglio seal, seen here in situ next to one of the radiating mud-brick walls.
An additional six copies of these tablets, again all with the same inscriptions, were found elsewhere in the debris outside of perimeter wall  including two near the group of 16 and two in debris between the perimeter and curtain walls.
View of the reverse of the elephant seal (H2000-4474/8994-01) from the Kot Diji phase levels, shows manufacturing marks and traces of a perforated knob or boss that is characteristic of Early Harappan seals.
Obverse of an unfinished elephant seal (H2000-4474/8994-01) in steatite from the Kot Diji phase levels at Harappa. This is the earliest seal with an elephant motif known from the region and may have been a prototype for later Indus seals.