Annuli form when the horn growth stops.  In temperate species, that occurs in winter.  So the technique only works in seasonal environments - in hot places like parts of Pakistan, horn growth may stop in summer, or it may even stop twice a year.  The same problem would apply to teeth.

Waseem bhai, check your email.

If you are a scientist stack in a laboratory from teeth: using growth layers in the cement of teeth or by actual wear of teeth,

 SPINAGE, C. A. (1973), A review of the age determination of mammals by means of teeth, with especial reference to Africa. African Journal of Ecology, 11: 165–187.

but there are other possibilities :

MORRIS, P. (1972), A review of mammalian age determination methods. Mammal Review, 2: 69–104.

If you are field widlife person and you need to estimate age in the bush and you know your antelope species well you can use body/horn development 

Perissodactyla or artiodactyla. That will be my question

Annuli form when the horn growth stops.  In temperate species, that occurs in winter.  So the technique only works in seasonal environments - in hot places like parts of Pakistan, horn growth may stop in summer, or it may even stop twice a year.  The same problem would apply to teeth.

This paper on Gaur might also interest you - http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2907.2010.00166.x/abstract

IIn the area where I work, in the Negev desert in the southern part of Israel there is a large population of Nubian ibex (Capra nubiana). Also the area is extreme desert there are annual growth rings on the Ibex horns. The rangers of the Nature and Parks authority that work here developed interesting method to estimate the age of each individual based on those rings.

age =number of rings / 1.5

Thanks Dear Guy Rotem, Marco Festa-Bianchet and Rachakonda Sreekar,

Waseem