[Advaita-l] Animal sacrifice in yagnas

[Neelakanta, Nataraja]

Dear All,
 
There is a practice of animal sacrifice in all the yagnas (by yagna, I
mean only shrouta yagnas like somayaga, agnistoma, garudaschayana). I
completely agree with the concept of the same, saying that, the
animal(goat) will attain Suryaloka, which is very tough to attain even
by us, being humans. First, a person can join vasu gana, then rudra gana
and next is aditya gana or surya loka. Even when a person passes away,
in the structure of paitrumedhika prayoga (last rites), this is what is
followed.
 
Now my question : Are there provisions for not doing animal sacrifice ?
There are some references in Mahabharata, wherein, Lord Yama says 'I
have made one person to perform yagna with pistapashu
(purodaasha),(pistapashu means animal kind of doll made out of dough).
And this is what is very auspicious'. 
 
But, the main problem lies here : Whenever there is conflict between the
Shruti and Smruti, you should override Smruti to consider Shruti. So, in
such a case, animal sacrifice will become a must while performing
yagnas.
 
Does anyone have any reference from Shruti, where in, it says there is a
provision for not doing animal sacrifice ?
 
Best Regards,
nattu