Let see the earliest big seal script for another character of Pig
on the left is like a character Dog, and on the right, it is character 者, which means cooking including grilling, and boiling (see Post 220). The character means "grilling the pig (pork)" in the early time, "boiling the pig (pork)" in later time. It is formed by two characters, and called ideogram character.
Why does the character mean Pig right now? I don't know.
The small seal script for the character is
in which, the left is 豕 (not radical of dog), right part is similar to that in big seal script.
The clerical script for character 猪
The left is radical of dog, and the right is 者, same as the big seal script.
So the left radical is either of radical of 豕，or radical of 犬 （dog).
The song type face for traditional character is
豬similar to small seal script.
Song typeface for simplified character is
猪which is similar to big seal script.
豕 is not used to be a radical in simplified Chinese any more, replaced by radical 犬. It is good to eliminate a radical, but lost the pictography of 豕 for pig related character.
豕 and 豬 both mean Pig, the 豕 is used more in writing, 猪 is used in oral and writing.
The pinyin for 猪 is Zhu1.