“The use of animals to represent human beings was probably directly influenced by the symbolism of Dan 7 and 8, although the fact that Jacob and his descendants are depicted specifically as sheep no doubt reflects the idea, widespread in the Old Testament, that Israel is the sheep of God’s pasture.”
Both of these statements are problematic, though the first much more so than the second. I won’t give my full rebuttal here (I’ve got a full appendix on the subject in my MA thesis), but the parallels between the AA and Dan 7 and 8 are almost non-existent in my opinion. I’d go so far as to say that they are little more than parallels in genre (though the author of the AA probably knew Dan 7-12). The specific content as well as the rhetorical drive of the AA and Daniel are totally different, and the use of animal imagery is also completely different. Note that animals never represent specific people in Dan 7, and in Dan 8 none of the specific people represented is a Jew. Moreover the animals of Dan 7 are all composite monsters (i.e. creatures with bits from lots of different animals), and not at all reminiscent of the animals found the AA. The same could be said for the animals of Dan 8 which, though they are not composite monsters, are decidedly fantastical as they roam over the whole world. Again, not particularly reminiscent of the AA.
The second bit, that the use of sheep is connected to the common imagery of God’s people as sheep in the OT isn’t wrong so far as it goes. Certainly the sheep/shepherd image permeates the OT and is particularly important in later prophetic works (Zech, Ezek). But the assumption that this is the primary reason that the author of the AA selected sheep and rams as the image to represent the people of Israel ignores completely the fact that all of the antediluvian fathers and the eschatological people are not represented as sheep but as bulls. This suggests to me that, though there may be a tangential connection to the sheep/shepherd metaphor in the AA, some other factor is driving the selection of animal imagery in the AA generally.
What is that other factor? Simply put, the AA is all about clean/unclean divisions. Who is clean (i.e. elect) and who is unclean (i.e. non-elect) is possibly the single most important idea in the AA and is used as the criteria for the selection of all of the animal imagery in the allegory.