This is mentioned in ayodhya kand-
"aiNeyam maamsam aahR^itya shaalaam yakSyaamahe vayam | kartvyam vaastushamanam saumitre cirajiivabhiH || 2-56-22
- saumitre= Oh, Lakshmana!; aahR^itya= being; aiNeyam maamsam= bring meat of the antelope; vayam= we; yakshyaamahe= shall worship; shaalaam= (this) leaf-hut; vaastushamanam= purifactory ceremony on entering the house; kartavyam= on entering the; chirajiivibhiH= by those who wish to live long.
Oh, Lakshmana! Bring the meat of an antelope. We shall perform a purifactory ceremony while entering the house. Which is to be done by those who wish to live long."
"mR^igam hatvaa.a.anaya kshipram lakshmaNeha shubhekshaNa kartavyaH shaastradR^iSTo hi vidhirdarmamanusmara || 2-56-23
- shubhekshaNa= Oh, large-eyed; lakshmaNa= Lakshmana!; hatvaa= killing; mR^igam= the antelope; kshhipram= quickly; anaya= bring; iha= here; vidhiH= the prescribed rite; shaastra dR^iSTaH= according to scriptural point of view; kartavyaH hi= indeed is to be done; anusmara= keep in mind; dharmam= the sacred obligation.
Oh, large-eyed Lakshmana! Killing the antelope quickly, bring it here. The prescribed rite according to scriptural point of view indeed is to be performed. Keep in mind the sacred obligation.”
"raamaH snaatvaa tu niyataH guNavaan japya kovidaH | samgraheNaakarotsarvaan mantran satraavasaanikaan || 2-56-29
- raamaH= Rama; guNavaan= the virtuous man; japyakovidaH= and the learned man in chanting of prayers; snaatvaa= after taking bath; niyataH= with subdned mind; samgraheNa= briefly; akarot= chanted; sarvaan= all; mantran= the sacred scripts; satraavasaanikaan= which are to be chanted at the end of a purifactory ceremony.
Rama, the virtuous man and the learned man in chanting of sacred spells, after taking bath and with subdued mind, briefly chanted all the sacred scripts to be chanted at the end of a purifactory ceremony."
What kind of purifactory rite is done with antelope meat- is this mentioned in any of the Vedic rituals?