Bonjour Monika,
à partir d'animaux -> "animaux" is not specific
à partir des animaux -> "des" (de + les) suggests "the animals"
Also, in the last example, something would be expected to follow:
à partir des animaux de la ferme = with the animals from the farm
à partir des animaux que tu as élevés = with the animals you reared
I hope this is helpful.
Bonne journée !
