Identification of Biomarkers of Stress in Meat of Pigs Managed under Different Mixing Treatments

Aims: The objective of this work was to apply the proteomic approach for identification of animal-based stress biomarkers during pig muscle maturation.

Study Design: Pigs were subjected to management treatments that may promote stress, like mixing unfamiliar animals on farm and/or during transport and lairage before slaughter. Three pre-slaughter treatments were applied: UF-UTL (Unmixed on Farm - Unmixed during Transport and at Lairage), MF-UTL (Mixed in Farm - Unmixed during Transport and at Lairage) and MF-MTL (Mixed in Farm - Mixed during Transport and at Lairage).

Methodology: Fifteen entire male pigs were used in this experiment. At slaughter, blood samples were taken for biochemical analysis. Meat quality traits (pH, electrical conductivity, drip loss, meat colour) were measured and muscle samples from the Longissimus thoracis were taken within the first 24 h post-mortem and used for analysis of total antioxidant activity (TAA) and sarcoplasmic protein profile study by SDS-PAGE.

Results: Mixing treatments (MF-UTL and MF-MTL) provoked faster muscle pH post-mortem decline (P= .009), lower total antioxidant activity (P< .001) and changes in some key proteins, like the heat shock 70kDa protein-1B (P= .040), glyceraldehyde-3-phosphate dehydrogenase “GAPDH” (P= .047), lactate dehydrogenase-A “LDH-A” (P< .001) and adenylate kinase isoenzyme-1 “AK-1” (P< .001). Furthermore, serum molecules related to fat metabolism (LDL-cholesterol and triglycerides) and changes of muscle proteins involved in the adenine nucleotide metabolism (AK-1) and glycolysis regulation (piruvate kinase “PK” and GAPDH) allowed accurate prediction of muscle pH and discriminated correctly 87% of meat samples into “no-mixing” or “mixing” treatments.

Conclusions: Early monitorization (within 24 h after slaughter) of selected biomarkers could be used in the meat industry as a tool for detection of situations of pre-slaughter stress related to animal mixing practices. However more research is needed in order to validate these results on a broader animal population.