And there is a disagreement with respect to when one says עגל בן בקר (bull-calf) and פר בן בקר (young bullock):

There are some who say that for an עגל בן בקר – the word בן is like בן חיל (hero); an עגל that is a בקר, meaning that it becomes an adult in its second year according to the sages. And פר בן בקר – the word בן indicates young like בני יונה (young pigeons), בני נשר (young vultures), and it is in its third year.

And there are some who say a בן בקר – is an עגל from the בקר species, since עגל is found with respect to other species like גדי, עיר, כפיר עופר, and the Torah never mentions sacrifices of a פר alone, only sacrifices of a פר בן בקר.