Interpretive Summary: Pre-slaughter handling practices and their effects on animal welfare and pork quality
By: Megan LaFollette
In February 2018, Journal of Animal Science published an article that reviewed the current research on pre-slaughter handling effects on behavioral and physiological responses in pigs and provide recommendations to minimize animal losses and pork quality. Pre-slaughter handling occurs at several points including just prior to and including loading, transportation, unloading, lairage, stunning, and exsanguination. Negative handling effects include decreased animal welfare – including animal loss – and carcass and meat quality issues causing carcass depreciation.
The farm of origin is the first major source of impactful pre-slaughter handling practices and contributes to 25% of dead-on-arrival and non-ambulatory pigs at the plant. Pigs raised in barren environments are more difficult to handle, fight more during mixing, have higher salivary cortisol, and have higher exsanguination blood lactate. Long-term fasting can increase pig frustration, fatigue, and excitement because of hunger which can increase fighting, skin lesions, and pork with dark, firm, dry characteristics. Finally, the move from the home pen to truck gate can increase several physiological stress indicators – and dead-on-arrival pigs and downers – especially when long distances are walked, pigs are newly sorted, and electric prods are used.
Transportation to the slaughter is the next area of concern. For vehicle design, when pigs must be moved through fixed decks and ramps within the vehicle – such as in pot-belly trailers – there is a greater risk of dead-on-arrival pigs, PSE pork (pale, soft, exudative), and negative physiological changes. Inside the vehicle, high ambient temperatures above 17 and 20 °C are associated with increased animal losses and open-mouthed breathing which are particularly seen in pot-belly trailers and during stops greater than 30 minutes. Low ambient temperatures can also have negative effects such as increased slips during loading, frostbit, and dead-on-arrival pigs particularly in vehicles with low boarding.
Lairage and the move to stunning are the final areas of concern. Short lairage intervals (less than 1 h) may result in increased PSE pork while very long lairage intervals (overnight or 15 h) may result in increased DFD pork (dark, firm, dry) and increased aggression. While moving pigs to stunning, poorly designed handling systems and large groups may result in increased slips, electric prod use, and vocalizations associated with negative behavioral and physiological responses and decreased meat quality.
Overall, this article makes several recommendations. At the farm of origin, (1) house pigs in enriched environments, (2) withdraw food 16-24 hours prior to slaughter, (3) move pigs to shipping rooms at least 2-4 hours prior to loading, and (4) use plastic boards and flags rather than electric prods. During transportation, (1) use caution with pot-belly trailers (2) at high temperatures keep pigs cool by water sprinkling or fan ventilation, (3) at low temperatures fit vehicles with 90% boarding, sufficient, bedding, and 5-cm Styrofoam insulation on the ceiling of the upper deck, and (4) unload pigs within 30 min to 1 h by compartment in small groups. At lairage to stunning, (1) pigs should be kept for 2 to 3 hours, (2) electric prod use should be kept to a minimum, and (3) well-designed handling systems and smaller groups should be moved during prior to stunning.