Today I was exposed to the fact that the female form of dog is bitch (just like bull (m) and cow (f)).
But I have never heard someone who called his female dog a bitch. So I suspect that in fact it is not in use, Isn't it?
In the UK, you can still use the term bitch without embarrassment, providing that the context is clear:
Our bitch, Sally, has just had pups.
However, you might want to think twice before referring to someone else's dog as a "bitch".
I have the feeling that the term is falling out of use, partly because most dogs are given names and so it can easily be avoided. You can still hear the term on British television, mostly on nature and countryside programmes.
Thinking about it, a lot of gender-specific names for animals are used infrequently. You rarely hear male ducks called drakes, male geese called ganders, or female cats called queens. However, male cattle are still called bulls, and male sheep are still called rams, but then these are farm animals and that may be why the usage has persisted.
In the U.S., it is only used in veterinary and dog-breeding circles. Outside of that, it is almost exclusively used as a pejorative.
British veterinarians and veterinary associations routinely use "bitch" to refer to female dogs and "dog" for males, particularly in the context of reproductive health.
BVA strongly supports the practice of neutering cats (castration of tom cats and spaying of queens) and dogs (castration of dogs and spaying of bitches) for preventing the birth of unwanted kittens and puppies and the perpetuation of genetic defects.
from https://www.bva.co.uk/News-campaigns-and-policy/Policy/Companion-animals/Neutering/ - there are many more examples on the same page.
Owners and the general public do it much less, and while they usually won't be offended, some may not even associate "bitch" with "female dog".
I suspect the use of the gender specific terms is easier in a professional context where the health implications are immediately useful to know.
That said, dog breeders in the UK use the term, and vets tend to use the same language as their clients. If the client says bitch, so will the vet; if they say its a "girl dog", so will the vet. A lot of the job is establishing a good relationship with the client.
source - asked my partner, a UK vet.
If you look at this Google Ngram, you will see the rise of the usage of the term 'bitch' in written works over the years.
Having said that, if you look at the frequency values of its usage (the scale on the left-side), you will notice how rarely they are used.
The word 'bitch' has been often marked as an offensive term nowadays. When someone shouts out:
"Hey, look at that bitch !"
people will expect to see a woman* (or man, no offence intended), and not a female dog.
Literally, the word means a female dog, but today, it is considered as a term that has been deemed as an offensive slang usage.
Now, if you ask why a cow is still called a cow, or a bull, based on it's gender and why bitch is not often used to reference a female dog, I'm as clueless as the next guy.
But please restrain from using the term as the listener will take offence and he wouldn't have the patience to listen to your justification that you had indeed referenced a female dog, by calling out so.
Fun Fact: A female pig is called a gilt or a sow. But I'm sure most people are unaware of this terminology.
"Bitch" is the word you use when you need to distinguish between male and female dogs. All English-speaking dog owners worldwide will use it for that purpose. It's the correct word to use, and in that context it is entirely clear that this is what is mean. Owners may say they have "two girls and one boy" instead, which is a natural extension of the tendency to treat dogs as children and members of the family.
If a dog owner doesn't have to be specific about whether the dog is male or female, they generally won't be. In that case, "dog" is the generic term for both male and female familiar canines. If a dog owner has to be specific about the animal being female though, the word "bitch" is entirely relevant, and no dog owner should be offended by it.
Outside of the doggy world though, "bitch" will almost always be an insult. The insult "dog" used to also be common - Samuel Pepys, on being woken by his friends at 3am, reports saying "What, is it you, you dogs!" - but has fallen out of use in English. Various other languages still use it, but in English it seems comically archaic (think of translated communist Chinese propaganda about "capitalist running dogs").