Hajj is a religious duty on Muslims. It must be carried out by each Muslim once in the life who has enough resources and bodily vigor to go to Makkah and perform the Hajj. Hajj normally falls between 8th to 12th of Zil Hajj. It is the last Islamic calendar month.
Sacrificing animals usually goat or sheep is also done during Hajj, but many people sacrifice cows or camels. A goat can be offered as sacrifice from one person but cow can be shared between seven persons. Islamic Development Bank has sets up booth around Makkah and Mina to sell the slaughtering coupons for sacrificial animals.
Sacrificing camel is the Sunnah of our Holy Prophet (peace be Upon him) but he also sacrificed other animals. There can be seven shares in the sacrifice of camel. The camel should be of five years age before sacrificing. The camel of any animal for sacrifice should not be sick, wounded or crippled. 10th of Zil Hajj is the proper day for sacrifice but it can be done till 13th.