The Relationship Between Exsanguination Lactate and Pork Quality

Introduction

Physiological changes associated with immediate pre-slaughter stresses, i.e. increased exsanguination blood lactate concentration, have been shown to have detrimental effects on pork quality causing increased drip loss and lighter color (Hambrecht et al., 2004, 2005; Warriss et al., 1994, 1998). These studies have focused on animal management and stressors immediately before slaughter, not during the entire marketing process.

Objective

The objective of these studies was to determine the relationship of preslaughter animal management, from the farm to the meat processing plant, on meat quality.

Materials and Methods

• Two studies were conducted at different locations
  • Midwest US (Study 1 n=80, n=144)
  • Quebec, Canada (Study 2, n=128)
• Study 1 : (Exp 1&2) Each test animal was sampled 7 times during the market process using a low-stress blood sampling procedure: (1) baseline at the farm, then following (2) loading, (3) transport, (4) unloading, (5) lairage, (6) movement to stun and (7) exsanguination.
• Study 2: Low-stress loading – flat ramp, hydraulic deck. Each test animal was sampled at exsanguination only.
• [LAC] was measured using a hand-held lactate analyzer (Lactate Scout, EKF-diagnostic GmbH, Magdeburg, Germany). Measured C.V. was 2.8%.
• Animals were electrically (US) or C02 (Canada) stunned and exsanguinated.
• Meat quality measurements were taken: 45 mm pH (Study 1) or 60 mm pH (Study 2), drip loss, color score (visual and Minolta), 24 hr pH, and glycolytic potential.
• Statistical Analysis: Pearson correlations were performed to relate [LAC] at all sampling points for each individual animal and differences in [LAC] between sampling points with meat quality parameters.

Results and Discussion

• A low-stress blood sampling procedure was developed requiring approximately 45 sec. per pig sampled
• [LAC] was highest following loading and at exsanguination (P=0.0001 – Figure 1) indicating areas of focus to improve animal handling during marketing.Figure 1: Blood lactate concentrations for Study 1 at the seven sampling points and Study 2 at exsanguination

• Increased [LAC] during loading at the farm resulted in improved meat quality, i.e. increased 24 hr pH (P < 0,002), decreased L* (P < 0.03) and decreased drip loss (P < 0.02). (Study 1 , Exp. 1 & 2 – Table 1).
  

  Table 1: Post-loading blood samples. Pearson correlations: [LAC] vs. meat quality measurements

  	Study 1 Exp 1 N=66-74	Study 2 Exp 2 N=106-136
  [LAC] (mM) Range	4.7 – 0.4 1.2-16.9	7.1 – 0.4 1.5-24.3
  24 h pH	0.36, P=0.002	0.40, P=0.0001
  L*	-0.25, P=0.03	-0.29, P=0.001
  Drip Loss	-0.28, P=0.02	-0.28, P=0.002
  GP	-0.18, P=0.14	-0.16, P=0.11

• Increased exsanguination (LAC] resulted in reduced pork quality, i.e. decreased 60 min post mortem pH (P=0.0004) and increased drip loss (P=0.02), indicating a more rapid rate of post mortem metabolism. (Study 2 – Table 2) consistent with work of Hambrecht et al., (2004) and Wariss et al., (1994).
  

  Table 2: Exsanguination blood samples. Pearson correlations: [LAC] vs. meat quality measurements

  	Study 1 Exp 1 N=66-74	Study 1 Exp 2 N=104-132	Study 2 N=118-119
  [LAC] (mM) Range	6.6 – 0.4 1.1-18.4	6.6 – 0.3 1.4-20.6	8.9 – 0.2 4.0-19.7
  60 min pH	0.03, P=0.79	-0.25, P=0.004	-0.32, P=0.0004
  24 h pH	0.23, P=0.05	0.06, P=0.47	0.01, P=0.90
  L*	-0.10, P=0.38	-0.22, P=0.01	0.09, P=0.31
  Drip Loss	-0.13, P=0.27	-0.20, P=0.03	0.22, P=0.02
  GP	-0.11, P=0.37	-0.12, P=0.23	-0.14, P=0.15

• Exsanguination [LAC] was not related to ultimate meat quality in Study 1. (Table 2) Proposed reasons for lack of relationship:
  • Lower level of handling stress in Study 1 stunning area.
  • Correlation between [LAC] at loading and [LAC] at exsanguination (P=0.003, Study 1) suggesting that animals with high [LAC] at loading tended to also have a high [LAC] at exsanguination.
  • Therefore, the effects of loading stress to improve meat quality predominated over the negative effects at exsanguination.

Conclusions

These data show that [LAC] was highest at loading on the farm and at exsanguination indicating areas of focus to improve animal handling during marketing.

These data also show that high [LAC] during loading is associated with higher ultimate pH, darker color, and lower drip loss. Therefore, improving pre-slaughter handling at the farm during loading will not necessarily translate to improvements in fresh pork quality traits.

With low-stress loading hihger exsanguination [LAC] was associated with a higher rate of early post mortem metabolism and increased drip loss.

References Cited

Edwards, L.N. 2009. Understanding the retationships between swine behavior, physiology, meat quality, and management to improve animal welfare and reduce in-transit losses within the swine industry. PhD. Thesis, Colorado State university, Ft Collins, CO,USA.

Hambrecht, E., J.J. Esisen, D.J. Newman, C.H.M. Smits, L.A. den Hartog, and M.W.A. Verstegen. 2005. Negative effects of stress immediately before slaughter on pork quality are aggravated by suboptimal transport and lairage conditions. J. Anim. Sci. 83: 440-448.

Hambrecht, E., J.J. Esisen, R.I.J. Nooijen, B.J. Ducro, C.H.M. Smits, L.A. den Hartog, and M.W.A. Verategen. 2004. Preslaughter stress and muscle energy largely determine pork quality at two commercial processing plants. J. Anim. Sci. 82: 1401-1409.

Warris, P.D., S.N. Brown, S.J.M. Adams and I.K. Corlett. 1994. Relationships between subjective and objective assessments of stress at slaughter and meat quality in pigs. Meat Science. 38: 329-340.

Warris, P.D., S.N. Brown, T.G. Knowles, J.E. Edwards, P.J. Kettlewell, and H.J. Guise. 1998. The effect of stocking density in transit on the carcass quality and welfare of slaughter pigs: 2. Results from analysis of blood and meat samples. Meat Science. 50: 447-456.