there's an interesting discussion about this here: http://en.wikipedia.org/wiki/Gender_reform_in_Esperanto
Most Esperanto words are actually today gender neutral unless otherwise specified. As it is also mentioned in the Tips and Notes section.
Bovo = cattle, ox or cow
Bovino = cow (if important to specify)
Virbovo = ox (if important to specify)
Honestly unless you are a farmer such specification will be of no need 99% of the time.
Family words and similar though like brother, father and king are male without the prefix -in-.