Offtopic: this made me chuckle a little bit since reminded me of "stara kobyła" (стара кобила; an old mare) which is an extremely derogatory way to call an old woman in Bulgarian (actually, even not that old).
I am not the person who would use it, but just out of curiosity, is there a similar expression that gets used in Polish in such occasions?
Oh, sorry, I mixed it up with the German word (die Stute), I think it should be "mare" in English, but I am not entirely sure. By the way, is "kobyła" the proper word for the female companion of a "koń" in Polish? In my dictionary I also find "klacz" to mean the same and I am a little bit confused.
Horses were for a long time very important in Polish every day life, culture and army, so there are many words to describe horses, but the times has changed, and nowadays their exact meaning is somewhat blurred. However, I would not agree, that "kobyła" is derogatory term towards a female horse - no dictionary says so. It is just a female horse. Maybe it is more colloquial than "klacz". Also, the milk of a mare (female horse) is called "kobyle mleko" or "mleko kobyły", sometimes "mleko klaczy" (but never "klacze mleko") - so perhaps "kobyła" relates more to a mare that has given birth to a foal, and "klacz" is a female horse in general.
Other terms to describe horses are "chabeta", "szkapa" (it means rather older, tired or unkempt female horses). Male horse is "ogier" (stallion), foal is "źrebak" or younger one is "źrębię", "źrebaczek".
There are also names related to the colour of the fur: "bułanka", "kasztanka", "siwka", "karuska" (reddish, brown, grey, black) - male versions are "bułanek", "kasztanek", "siwek", "karusek". Also male are "gniadosz" (reddish or brown with black tail and mane - I do not know if there is female version) and "deresz" (mixed colours, with head, neck and legs mostly reddish, brown or black and body is greyish white).
Also, it is worth to note, that "kobyła" means also 1. a piece of reading (a book, a poem, a theatre play script) that is very long or difficult to read through or master; 2. an exam that covers large portion of material to study and is difficult to pass.
The term "stara kobieta" is offensive just like an old woman in English.
Terms like: "starsza kobieta" or "kobieta w podeszłym wieku", "kobieta po sześćdziesiątce, siedemdziesiątce, osiemdziesiątce...) (an elderly woman, woman in her sixties, seventies, eighties... ) are neutral and respectful.