The detail list of all animals, birds and marine creatures which were tied in Yajna-Shala is present in Ashwamedha
Prakarana of Vajaseniya samhita of Shukla Yajurveda. The 24 adhyay of Shukla yajurveda samhita is only dedicated for description of those animals and the respected gods for whome they were tied to pole.
The creatures mentioned are as follows.
Horses ( one with black belly ,one who's back portion is white or
black) , Bull with no horns , NeelGai or blue bull , goat with black
neck , pied crested cuckoo (Chatak ), Pell or Titar,Kakar bird ,
Vikakar bird, Dolphin ,a marine creature called Nakra , Baguli bird ,
water crow , Chakwa bird , Uluk bird ,Nilkantha bird , peacock , Kapot
bird , Baya bird ,GhuyaTal bird , Kulik bird ,Parushni bird , crow
,peagon , eagle ,deer of various types (ruru ,rushya) ,camel ,
elephants , mosquito, Weevil or bhunga , monkeys , a aquatic creature
named Sus , red snake , bird that eats lotus flower , honeybee , white
deer , maina bird ,lion , wolf , parrots ,water hen , tortoise , blue
deer ,goha ,kalaka ,kathphod birds ,Cuckoo , female rat , wild sheep ,
phyton , dog of black color , donkey , rhino ,girgit (Chameleon), papiha and
shakuni bird , crocodile ,swan, Vikakar bird ,Kakar Bird ,Baguli bird ( >Heron) , sarus crane ,Nilakantha bird ,Lava bird , Parushna Bird (gull) ,Cichapu bird , kash bird , small larvas ,Paraswat deer ,Red deer ,Tiger , Pushat deer, goat.
I am providing some of the verses here.
एण्यह्रो मण्डुको मूषिका तित्तिरिस्ते सर्पाणां लोपाशा S अश्विन: कृष्णो
रात्र्या S ऋक्षो जतु: सुषिलीका त s इतर जनानां जहका वैष्णवी ।।36।।
For anha devata female deer , for vanspati deva , Kalaka and
Kathphod bird and goha bird , Tamrachur bird for savita , swan for
vayudeva ,for sea god crocodile ,Nakra and kulipaya , and for hri god
the creature called sehi.
प्रजापतये पुरुषान्हस्तिन S आलभते वाचे
प्लुषिम् श्चक्षुषे मशकात्रछोत्र्त्राय भृङ्गा:।।29।।
For the prajapatis elephants ,for Vaak devata Plushi , for Chakshu
devata mosquito ,for Shrotra (ear) god bhunga.
शिशुमारानालभते पर्जन्याय मण्डूका न्द्भ्यॊमत्स्यान्मित्राय
For sea dolphins ,for Parjanya(rain) god , toad , fish for water deity
,for mitra deva and Kulipaya Varuna a creature called Nakra.
वसुभ्य s ऋश्यानालभते रुद्रेभ्यो रुरूनादित्येभ्यो न्यङ्कुन्विश्वेभ्यो
देवेभ्य : पृषतात्न्साध्येभ्य कुलुङ्गा न् ।।27।।
For Vasus a kind of deer called rushya , for rudra a kind of deer
called ruru , Nyanku deer for adityas , spotted deer for vishwadevas
,for sadhyadevas a kind of deer called Kulunga.
It's explained in the translation of the Yajurveda Samhita that by the author all those creatures after the ashwamedha yajna were released free. None were slain during those times.
So considering this fact they were only tied and not killed. So may be sacrificing all the animals are not part of standard ritual.