It is actually quite difficult to find out a proper translation without betraying the Latin and classical spirit!
In the Latin world the importance of animals is mainly about what they represent: love for example (the passer of Catullo to Lesbia), they are messengers of human feelings.
But they can also represent human virtues and vices, stereotyped and even stigmatized behaviors (just think to Phaedrus and its fables).
Nevertheless, if you are looking for an exact translation to "No virtue in being a humankind", we can easily express it as
Nulla virtus in esse homo.
However, I would suggest also another sentence, that in my opinion strictly links humans and animals, without removing any virtue from both. No classical reference, just me, so see if you may like it...
Homines prosint animalibus et animalia hominibus, meaning "Let humans be of benefit to animals, and animals to humans"; which probably is also related to the office in question and the veterinary work.
Note that, in classical Latin at least, you can't make esse (or any other infinitive) the object of in (or any other preposition). Or perhaps this is a Medieval or later construction that aims to imitate a Greek articular infinitive?
You are perfectly right, this construction is Medieval:
In his De decem praeceptis (Collatio V), S. Bonaventura writes "In esse naturae filius non est coaequus patri". There are also other examples of the same expression, even stronger than the often used in philosophy in esse, in posse.
As written in the comments, I took the freedom to choose the use of the nominative case. In general, this is not a mistake; in some grammars, where sometimes impersonal examples are displayed, it's easy to find the verb as an infinitive, and the subject in nominative:
Certainly, if we had an infinitive sentence (such as a subjective or an objective), we could only use the accusative case for the subject of the verb, but here, in the phrase I wrote, we have a substantivized infinitive, which does not make the sentence an infinitive one.