Veterinary Handbook Disease Finder



Other Names

  • Smothering
  • Strangulation
  • Suffocation



Asphyxiation is the condition or act of being deprived of oxygen. Strangulation implies compression of a tube such as the trachea (causing asphyxiation) or carotid arteries (causing interruption of blood supply to the brain). Smothering refers to crushing injuries (including strangulation and/or asphyxiation) when animals are trampled underfoot by pen mates. Misadventures causing compression of the chest, windpipe or carotid arteries occur occasionally in the export process, mainly on trucks during transport or in pens at sea.

Risk factors include overcrowding, poor yard or pen design, and use of excessive or inappropriate force in moving or restraining animals. These factors can create opportunities for animals to pile on each other, or be stuck under pen rails, and may make it difficult for fallen or downer animals to stand.

Situations where animals may pile on top of each other at sea include during very rough weather, when frightened, and during feeding when hungry animals may crowd at troughs, particularly if there is limited trough space. 

Windpipe and carotid artery compression may occur when necks are stuck in horizontal gaps between pen rails or vertical gaps above gate chains. Ropes, wire, chain or baling twine sometimes used to suspend broken troughs are choking hazards.

Inadvertent injury to the windpipe and carotid arteries may result from the use of lassoes to catch and restrain animals and when cattle go down in a head bail, particularly one with a head locking device. Wild or frightened animals are particularly at risk because they may struggle when restrained and throw themselves down.

Clinical Signs and Diagnosis

Individual or multiple animals may be found down, dead, or standing but injured. Survivors have heaving respiration which eases over time. Animals may suffer neck, back or leg injuries trying to extract themselves from unusual positions. Hair coat or fleece on one side may be entirely covered in manure if stuck in lateral recumbency for a period.

At necropsy, bruising under the skin on the thorax or upper neck, congestion of trachea and lungs, or petechial haemorrhages on conjunctivae, are all changes consistent with trauma from smothering.


Urgent reaction may be necessary to save stock from a life-threatening situation. The critical response is to remove the immediate cause of the asphyxia or strangulation. This may involve moving cattle or opening a head bail. In some cases it may require bending or cutting rails or ropes. Allow affected animals to recover to normal breathing before relocating to a less crowded pen for rest and confinement. Administer oral fluids and electrolytes if dehydration is present and the animal is unable to drink by itself. Inject non-steroidal anti-inflammatory drugs (tolfenamic acid, ketoprofen, flunixin meglumine, meloxicam) if soreness affects eating or walking.

Severely injured animals should be euthanised, particularly animals with limb fractures and irreducible dislocations.


Be aware of codes of practice governing space allocation for animals during transport. Ensure crew members have training in stockmanship to either avoid or respond quickly to situations where animals may be suddenly alarmed or subjected to undue handling pressure during movements. Emergency rescue equipment should be easily accessible (knife, bolt cutter and pipe cutter).

Avoid disruptions to feeding that cause the animals to become hungry. Ad lib feeding is recommended to prevent hunger. Ensure there is sufficient feed for the voyage so that severe rationing is not required at the end of the voyage. Maximise trough space per head where possible.

Recumbent animals at the front of pens near feed troughs should be encouraged to stand before feeding.

Always monitor animals closely during feeding, especially if they are at risk of smothering, and have vigilant people on hand to deal with pile-ups if they occur.

If there is a risk of smothering, feed out to one pen at a time and have a team of people ready to prevent and disentangle pile-ups. Keep pens dry to prevent slipping and bogging. Livestock on trucks or at sea should be inspected regularly throughout the day and night for early detection of misadventures. Always allow sufficient room on trucks or in pens for animals to stand up easily if they fall or lie down.

Use non-tightening catching ropes or halters whenever possible to restrain cattle in pens. Head bails should have vertical bars and a quick release mechanism to avoid choking if an animal goes down. Crushes with head locking devices should have movable V-shaped side panels that squeeze, preventing animals lying down.

Check pens for hazards. Design low risk pens with special attention to removable and adjustable rails, hinges and latches on gates, and positioning and securing of troughs.