Effects of different stunning methods on the welfare and carcass quality of finisher pigs in South African pork abattoirs

Abstract

The purpose of this research was to study the effects of different stunning systems on the welfare of pigs in South African abattoirs. Four stunning systems were evaluated: 84% CO2, emergency head-only electrical, standard head-to-heart electrical, and an experimental 80% Argon 20% CO2 (Ar-CO2) admixture. pH data, pig behaviour inside the stunner and muscle metabolites were studied in this research. Both the Ar-CO2 and emergency head-only stunning methods were deemed problematic on the basis of animal welfare. The Ar-CO2 method had the sharpest and fastest pH decline. The 84% CO2 and standard electrical head-to-heart stunning methods had similar rates of pH decline, with CO2 having a lower pH than electrical stunning at every point. The behaviour displayed during gas stunning treatments was recorded by way of cameras located inside the stunner. Those stunned by 84% CO2 lost their consciousness significantly faster than those stunned by Ar-CO2. During the Ar-CO2 stunning, four out of five pigs squealed while under the admixture’s influence, indicating that the animals were distressed during this process. Squeals were not heard while the pigs were exposed to the 84% CO2. pH profiles did not differ significantly between head-to-heart electrical stunning and 84% CO2 stunning, implying that the stunning treatment itself did not have a big effect on the post mortem pH and its decline. The author recommends that further research in the South African pork industry be focused on improving and refining current CO2- and electrical stunning systems. Pre-slaughter handling plays a big role in the animal’s psychological- and physiological state during stunning and must be further improved upon.