Neural Pathways

In a recently slaughtered commercial meat carcass, motor neurons in the ventral horn of the spinal cord receive both inhibitory and excitatory inputs, but the descending and ascending tracts that link the brain and spinal cord in meat animals are polysynaptic, so that motor neurons have a high degree of autonomy relative to the condition in humans.

Meat animals have only a small direct motor cortex in the cerebrum, only short motor tracts descend the spinal cord, and sensory areas of the cerebral cortex are dominated by inputs from the lips and snout while areas corresponding to the limbs and trunk are very small.

Source of Activity

Inhibition of Activity

EMG (Electromyography)

Reflex activity during slaughter may be seen by electromyography during the time that the carcass is handled after stunning, as in the example below, which shows EMG activity just before, during and after the point of exsanguination (at 0 sec).

EMG may reveal isometric muscle contraction in the shackled limb that is not otherwise easily visible.

Respiratory Reflexes

As the degree of reflex activity diminishes, the animal's respiratory reflexes become evident. Most commonly, the animal coughs and moves its head downwards or ventrally. This may be detected by EMG activity in the ventral muscles of the throat or by bouncing of the carcass, detected with a load cell in the shackling chain, as shown in the example below.

In this example, the upper line shows the bouncing of the carcass on a load cell in the shackling chain, while the lower line shows integrated EMG activity of the throat muscle. Thus, every time the head was pulled down by a postmortem reflex, it was detectable by both methods.

Commercial Importance

Reflex activity after stunning is important in the meat industry because it may hinder exsanguination, or accelerate muscle metabolism to cause PSE.