Short answer: In these lessons, the pronunciation is k'lavót (the first thing you said). If the noun were immediately in front of another noun--e.g., כלבות הילד, "the child's dogs"--then it would be kalbót (the second thing you said). However, this is the rule of the "Hebrew Academy" that determines proper usage; native Hebrew speakers are supposed to be the voices in the recording, and I see native speakers arguing for "kalbót", so the rule must not be in some people's speech.
Long answer: Both pronunciations are correct, depending on whether כלבות is in the absolute or the construct state. The construct state of a noun is used when the noun is "described" by the noun immediately following it: כלבות הילד = "the dogs of the child" / "the child's dogs". In these situations, כלבות is pronounced "kalbót". In other situations, the noun is in its "normal" absolute state, and the pronunciation is "k'lavót". That said, this is the official rule of the "Hebrew Academy" that determines proper usage for the language. The recording is supposed to have been done by a native speaker, and I notice native speakers in the forums who are arguing for "kalbót"; this suggests that some native Hebrew speakers do not distinguish between absolute and construct state for certain types of nouns (e.g., מלכות). (PS: The type of noun in question is called a "segholate" because of the "eh" seghol vowels in the corresponding masculine singular forms, like כֶּלֶב and מֶלֶךְ. The different forms for these words (masc./fem. sing./plur. absol./constr.) are complicated because they reflect a "broken plural" system that may have been original to the parent Semitic language and that is prevalent in Arabic. The important thing to know for these nouns is that beyond the consonant root X-Y-Z, the stem alternates between vowel patterns XeYeZ, X'YaZ-, and XaYZ- depending on the gender, number, and state of the noun. XeYeZ is used for masculine singular (both absolute and construct: כלב kélev), X'YaZ- for plural absolutes (כלבים/כלבות k'lavím/k'lavót), and XaYZ- for feminine singular (absolute and construct) and plural constructs (כלבי/כלבות kalvé/kalvót).)
Hope any of that helps! :)
Thanks for the detailed explanation (and to be sure, the construct plural is, by the formal rules, /kalvot/ and not /kalbot/). But I'd like to stress to foriegn learners of Hebrew here that virtually no one, no one, says /kalvot/ or /klavot/, everyone says /kalbot/ both for absolute and for construct (to the little extent that construct is used in spoken Hebrew; I think by now it's just in set pharses, but indeed lots and lots of set phrases). Moreover, with other rules that no one says (/u/ rather than /ve/ for "and" in some contexts), if you go by the formal rule many people will recognize and appreicate it; with this one, very few people know that it "should" be /kalvot/klavot/; most people will think you're just wrong.
My answer for the above question was "The bitches eat the food." because I thought "כלבות" was stipulating a group of female dogs however the answer was marked as incorrect. So I'm confused and thought maybe this was another exception to the rule and a feminine ending actually denoted the plural rather than "כלבים" being the plural for a mixed group of dogs.