In another translation from Chinese to English, I met this part -
Seventy-seven head of cattle.
As far as I remember English grammar, head in this case can be used instead of heads only if we say something like
Seventy-one head of cattle.
However, in any other case, we have to use heads, and the correct phrase would be
Seventy-seven heads of cattle.
Am I right?
Head when used as a unit of count for live animals has singular form ("head"). Thus, if you wish to discuss your herd of cows, you might say "I have seventy-one head of cattle on my farm".
a person or animal when considered as a unit
If you wish to discuss the severed heads of animals, e.g. in a butchery or meat context, you would use the plural form, and might well say "I have sold seventy-one cow heads (or cows' heads) to the dog food company". In the latter situation, a native speaker would be unlikely to speak of "heads of cattle".
the part of the body above the neck where the eyes, nose, mouth, ears, and brain are:
Seventy-seven head of cattle.
"Head" is an uninflected plural-only noun, i.e. it is not morphologically marked as a plural. Here the quantificational noun construction avoids the problem that arises with "cattle", where we can use high round numerals like "a thousand cattle", but not low numerals like *"seven cattle".
