Short answer. Yes. The Civil Code makes a deliberate exception for animals: while other fruits must be manifest or born to exist in law, it is enough for young animals that they are in the womb of the mother, although unborn. They count as fruits from that point.
What the law says
Only such as are manifest or born are considered as natural or industrial fruits. With respect to animals, it is sufficient that they are in the womb of the mother, although unborn.
Civil Code, Article 444 — When Fruits Are Deemed Existing. Read the full provision →
The general rule and the animal exception
The article sets a threshold before a fruit exists as a legal object at all: only such as are manifest or born are considered as natural or industrial fruits. A crop that has not yet appeared is a prospect, not a thing anyone owns. Then comes the exception, and it is stated as plainly as the rule — with respect to animals, it is sufficient that they are in the womb of the mother, although unborn. Young animals therefore count from conception rather than from birth, which is a lower threshold than the one applied to everything else.
Why animals are treated differently
The distinction is practical rather than philosophical. A pregnancy in a herd is ascertainable in a way that an unplanted crop is not: the animal exists, it is identifiable, and its offspring can be attributed to a particular mother in a particular herd on a particular date. Plants that have not yet appeared have no such anchor. Rather than leave the increase of a herd in limbo until each birth, the Code fixes the moment at which the young become part of the yield of the property, and it fixes it early.
What turns on the earlier moment
Timing is the whole of it, because fruits belong to the owner of the thing that produces them and the question is always who owned it when. If livestock is sold, mortgaged, inherited or made the subject of a usufruct while animals are carrying young, the unborn increase is already reckoned as fruits and is allocated accordingly — it does not wait for the birth and then attach to whoever happens to hold the herd by then. The same reasoning applies when someone must account for the produce of animals he held during a period that has ended.
How this is proved when it is contested
Because the rule fixes a date, the evidence that matters is the evidence of dates. Herd records showing which animals were carrying young and when, veterinary or breeding notes, birth records afterwards, and the instrument transferring or encumbering the animals with its own date on it are what settle the question. Contracts over livestock are worth drafting with this in mind: a clause saying expressly what happens to the increase removes the argument entirely. Where nothing was said, the rule in this article supplies the answer, and it supplies it from conception.