Farm Chickens and Eggs

If a Halal animal consumes only impure things to the extent that it creates bad odour in its meat and milk, then it will be Makruh to consume its meat and drink its milk.

However, if it consumes other things along with the impure, or if it does not create bad smell in its meat and milk, then the meat and milk will be totally Halal. (Radd al-Muhtar, 6/340)

It is stated in al-Fatawa al-Hindiyya:

“It is Makruh to consume the meat of a domesticated or free-range (jallalah) camel. And it (jallalah) is that animal which most of what it eats is impure. The reason being is that, if the majority of what it eats is impure, its meat will change and it will create a bad smell, thus it will be Makruh to consume it, as is the general ruling with foul and smelly food.”

It is further stated:

“A chicken will only be considered a jallalah if the majority of what it eats is impure, and that it penetrates into the meat in such a way that it creates a bad smell.” (See: al-fatawa al-Hindiyya, 5/289)

In view of the above, it becomes evident that factory/farm chickens in general are Halal. Yes, if the chicken ate impure things to an extent that it created bad smell in the meat, then surely it will be makruh to consume it. In other words the ruling of karaha (or impermissibility) will depend on the bad smell in the meat.

When the farm chicken is Halal, then its egg will also be considered Halal.
And Allah knows best