The effect of ante mortem electrolyte therapy on animal physiology and meat quality in pigs segregating at the halothane gene

The present study was initiated to investigate the effect of oral potassium (600 mg, slow release, 24 h preslaughter), intramuscular (IM) magnesium (500 mg MgSO 4 , 2 h preslaughter) or slow release magnesium (Magnesium-aspartate-hydrochloride (Mg Asp) 20 or 40 (g d −1 for 5 d) on animal physiology and pork quality. Experiments were undertaken on 318 barrows and gilts (100 kg ± 5 kg) represented by three genotypes segregating at the halothane locus (nn, Nn and NN genotypes). Experiment 1 indicated that the oral potassium effectively (P ≤ 0.05) reduced pCO 2 values in the nn genotype. Intramuscular injectable magnesium treatments were also found to raise plasma magnesium (P < 0.05) but did not alter muscle, liver or heart tissue levels. Both oral potassium and i.m. magnesium exacerbated subjective pork structure and texture scores but were found to increase muscle brightness and hue (higher b* value). In exp. 2, oral magnesium-aspartate (Mg Asp) was found to raise plasma, but not tissue, levels of magnesium. When fed to a group of halothane carrier pigs (Nn genotype), Mg Asp reduced muscle temperature 45 min post-stunning, increased muscle redness (CIE a* value) and reduced muscle drip loss (P < 0.06). It was concluded that oral potassium and i.m. magnesium as administered in the present study had no beneficial effects on pork quality but that the beneficial effects of Mg Asp on meat colour and drip loss may warrant further investigation. Key words: Magnesium, potassium, preslaughter, pork quality, PSE pork