The ad hit Ernst for not being strong enough on cutting spending, and used the chick to claim Ernst didn’t make a "peep" when it came to cutting pork.
You could roll your eyes and point out that the chick was used to illustrate the word "peep" and was responding to Ernst's ad featuring pigs, but imagine the outrage if a male Republican candidate featured a chick in a campaign ad against his female Democratic opponent.
A chick might be seen as a subtle sexist dig and if you're still rolling your eyes, think about all the "subtle" sexism the Left finds in every anti-Hillary Clinton argument, or the "subtle" racism supposedly found in every anti-President Obama argument.
Now consider the source of this ad: Braley. This is the same candidate accused of insulting farmers back in April, the same candidate running in an agricultural state who misspelled common farm terms and the same candidate who used a photo of an English farm on his website.