Please be aware.
This is from Iowa Law Statutes.
Popular Title: Dog Laws
Primary Citation: IA ST 351.1 - .43
Last Checked: December, 2013
Summary:
These Iowa statutes comprise the state's dog laws. With regard to damage done by dogs and dog bites, the owner of a dog shall be liable to an injured party for all damages done by the dog, when the dog is caught in the action of worrying, maiming, or killing a domestic animal, or the dog is attacking or attempting to bite a person, except when the party damaged is doing an unlawful act, directly contributing to the injury. Further, the law states that it shall be the duty of the owner of any dog, cat or other animal which has bitten or attacked a person or any person having knowledge of such bite or attack to report this act to a local health or law enforcement official. The section also contains general rabies vaccination provisions and a prohibition on dogs running at large (results in impoundment).
351.26. Right and duty to kill untagged dog
It shall be lawful for any person, and the duty of all peace officers within their respective jurisdictions unless such jurisdiction shall have otherwise provided for the seizure and impoundment of dogs, to kill any dog for which a rabies vaccination tag is required, when the dog is not wearing a collar with rabies vaccination tag attached.
CREDIT(S)
Amended by Acts 1961 (59 G.A.) ch. 193, § 9; Acts 1994 (75 G.A.) ch. 1173, § 33.
351.27. Right to kill tagged dog
It shall be lawful for any person to kill a dog, wearing a collar with a rabies vaccination tag attached, when the dog is caught in the act of chasing, maiming, or killing any domestic animal or fowl, or when such dog is attacking or attempting to bite a person.
CREDIT(S)
Amended by Acts 1994 (75 G.A.) ch. 1173, § 34; Acts 2007 (82 G.A.) ch. 111, S.F. 406, § 1.
HISTORICAL AND STATUTORY NOTES
Which means that if your dog is chasing cows the farmer is fully within his rights to shoot your dog.
Please don't take any more chances with your dogs life and keep it leashed.