Lightning and Livestock
October 24, 2012
Did you know that when an approaching thunderstorm rain front is up to 10 miles away, the risk of cloud-to-ground lightning strike begins*? For the safety of farmers and their livestock, proper grounding of barns, tall trees, and metal fencing is needed. Even when precautions are taken, lightning strikes can still affect cattle, horses, and other livestock. Preventative measures include grounding large trees, fences, and buildings, or fencing off large trees so that livestock cannot get close to them. Trees within 10 feet of a barn which are taller than the barn should be grounded to prevent flashover, a situation where the bolt leaps from tree to building.
Standing on damp ground near a large tree can increase the risk of lightning strike because the roots of the trees can act as pathways for the current if the tree itself is struck. Animals standing in a pond are also at risk because the water can become electrified.
Indirectly, lightning can produce livestock injury or death if overhead wires come down, trees fall onto them, or the barn is struck or contains faulty wiring.
Lightning may produce sudden death, burns or singed hair at point of contact, unconsciousness with a gradual return to normal, or residual ongoing nervous system problems (deficits). A minor shock will cause kicking, muscle activity and restlessness. During a thunderstorm, a shod horse standing under a large ungrounded tree on a high hill is a risky combination.
All of the risk factors that apply to animals also apply to people, and the damage done by lightning affects all animal species in a similar fashion, so farm workers need to take the same precautions recommended for livestock protection.
Veterinarians play an important sleuthing role by conducting post mortems (necropsies) to confirm the cause of sudden death in presumed cases of lightning strike. As other medical conditions can mimic lightning strike, laboratory tests are also run. Every now and then in the news, it is reported that a group of livestock is found dead in a field. Some fanciful reports have attributed these episodes to UFO landings because of unusual patterns of organ damage. More likely, these deaths result from lightning strike or another well-known cause of sudden death. Because lightning strike can occur miles away from the centre of a rainstorm, it may not be obvious to the farmer that a lightning injury episode occurred. It might also be a bit less obvious that lightning was the cause of death or injury if only a single animal was affected and the storm did not pass directly overhead.
* according to the Centers for Disease Control Morbidity and Mortality Weekly Report (Vo. 47, No. 19)