At Leviticus 11:6, the Lord, while narrating the standards that define animals which are clean or unclean for consumption by the people of Israel, describes the rabbit as follows: " The rabbit, though it chews the cud, does not have a divided hoof; it is unclean for you." . Now, Zoology does not enlist the rabbit among animals that chew the cud, through it appears to be doing so while eating its food. The Lord would have taken into account the said appearance of rabbit (of chewing the cud) while describing it as an unclean animal. But, before making any assumption, I would like to know if there are any official teachings from the side of Catholic Church available on the topic on why the rabbit was classified as unclean.
I find no reference to Leviticus 11:6 on the websites of the Vatican or the U.S. Council of Catholic Bishops (USCCB).
The USCCB does maintain on its website the text of the New American Bible (Revised Edition), or NABRE, which is the only translation approved for public liturgical use in the United States. The NABRE translates Leviticus 11:4–6:
4 But you shall not eat... the rock hyrax, which indeed chews the cud, but does not have hoofs and is therefore unclean for you; the hare, which indeed chews the cud, but does not have hoofs and is therefore unclean for you; ...
and has the following note on Leviticus 11:5–6:
According to modern zoology, the rock hyrax (Hyrax syriacus) is classified as an ungulate, and the hare as a rodent; neither is a ruminant. They appear to chew their food as the true ruminants do, and it is upon this appearance that the classification in the text is based.
This is far from a doctrinal statement; but it is as close as one is likely to get, having (as the entire NABRE has) the imprimatur, or permission from the bishops to be printed.
All the Catholic Haydock Commentary on that verse says is:
Ver. 6. Cheweth. Some copies of the Septuagint add not, which agrees with the nature of the hare; though the people to whom Moses addresses himself were of a different persuasion. Its hoof is not divided into two parts only, and therefore it is accounted unclean.