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European Journal of Applied Sciences – Vol. 12, No. 6

Publication Date: December 25, 2024

DOI:10.14738/aivp.126.17823.

Swatland, H. J. (2024). A Review of Abattoir Reflexes in Relation to Anaerobic Glycolysis and Meat Quality. European Journal of

Applied Sciences, Vol - 12(6). 19-28.

Services for Science and Education – United Kingdom

A Review of Abattoir Reflexes in Relation to Anaerobic Glycolysis

and Meat Quality

H.J. Swatland

Department of Animal Biosciences, University of Guelph

ABSTRACT

Current research on meat quality is dominated by correlative studies of animal

genotypes and histochemical fiber types, correlating features of live animals with

features of commercial importance in their meat. But between live muscle and

meat, there is an epigenetic realm where random factors mediated by animal

treatments and their nervous systems may have strong effects. They have the

potential to obscure real correlations between live animals and meat quality, or to

produce spurious correlations. Physiological studies in abattoirs may prove things

one way or the other.

Keywords: Electroencephalography, Electrocorticography, Electromyography, Meat

quality.

INTRODUCTION

A reasonable place to start for this historical review of the electrophysiology of meat is with

the discoveries of Luigi Galvani (1737-1798). Frog legs might be excluded from the definition

of meat by some authorities, but as striated skeletal muscle being prepared in a kitchen for

human consumption, this may be too restrictive and missing some great science. Galvani was

intrigued by the post mortem kicks of isolated frog legs hanging on metal rails in a kitchen.

This started discoveries in bioelectricity, the physics of electricity, and the literary fiction of

Mary Shelley (Frankenstein).

Meat science as we know it today, started in the 1930s with biochemists trying to understand

how a contractile and extensible tissue like striated skeletal muscle could undergo rigor

mortis to become a non contractile and almost inextensible food commodity – meat. Their

discoveries had an amazing scientific future. They discovered how calcium ions control

muscle contraction – and confirmed many of the key factors in our contemporary

explanations of muscle contraction – actin, myosin, sarcoplasmic reticulum, tropomyosin,

troponin, and sliding filaments [1, 2]

In the early days, an important adjunct to biochemistry was the physiological testing of

skeletal muscles as they became inextensible during the development of rigor mortis [3, 4].

The rigorometer was developed, new at the time for food scientists, but drawing on a century

of research by muscle physiologists [5]. However, this was a real paradigm shift.

Physiologists require muscle strips with slow post mortem metabolism so that muscle

contraction may be measured as a response to direct or neural excitation, whereas

rigorometers measure the loss of extensibility when a muscle strip going into rigor mortis is

loaded. This requires a supply of muscle immediately post mortem – many experiments

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Swatland, H. J. (2024). A Review of Abattoir Reflexes in Relation to Anaerobic Glycolysis and Meat Quality. European Journal of Applied Sciences,

Vol - 12(6). 19-28.

URL: http://dx.doi.org/10.14738/aivp.126.17823

genetic alteration of calcium release channels in the sarcoplasmic reticulum, but it is the basis

for understanding how abattoir reflexes affect meat quality, especially in pork, and who

knows how many other animals.

An experiment to look at the natural EMG activity in the porcine vastus lateralis muscle on the

non-shackled side (isotonic muscle contraction not prevented by shackling) is shown in Fig. 1.

Here the kicking of the free limb is seen (Fig. 1, A). A stimulatory electrode inserted near the

lumbar spinal cord (1 v square wave, 32 msec duration at 1 Hz) then caused an EMG response

and contraction for several minutes until it declined (Fig 1, C), but could then reactivated (Fig.

1, D) by increasing the voltage to 100 V until the response diminished (Fig. 1, E) and the EMG

electrode picked up the distant constant stimulatory voltage (Fig. 1, F). This showed that

reflex kicking in an unshackled limb was terminated by the central nervous system, not by an

inoperative peripheral nerve [10].

Fig. 1: EMG activity of free kicking in the vastus lateralis of a pig carcass (minutes postmortem).

Shackling a newly slaughtered pig by one hind limb causes a massive neurological response

possibly involving brain stem reflexes, Golgi tendon organs and neuromuscular spindles in the

free limb. Before shackling (time 0 in Fig. 2) there was diminishing EMG activity (as in Fig. 1,

A), now followed by bursts of kicking (Fig. 2, B and C), then slowly diminishing activity (Fig. 2,

D).

Fig. 2: Electromyography of isotonic reflex activity in the free limb of a pork carcass following

shackling at time 0.