EFFECT OF ORAL LOADING OF ACID OR BASE ON THE INCIDENCE OF PALE SOFT EXUDATIVE PORK (PSE) IN STRESS-SUSCEPTIBLE PIGS

Thirty-three halothane-positive pigs were assigned to one of three ad libitum water treatments 4 days prior to slaughter: control, sodium bicarbonate (12.6 g litre-1), or ammonium chloride (8 g litre-1) to study the effect of an oral acid or base load on post-mortem changes in the longissimus dorsi muscle and on ultimate pork quality. Eight halothane-negative pigs were also slaughtered as negative controls. Dietary ammonium chloride caused a metabolic acidosis as indicated by lower blood and urine pH, and lower blood bicarbonate in treated pigs. In halothane-positive pigs, dietary treatments had no significant effect on post-mortem muscle pH changes or on measurements of muscle quality (colour, drip loss, texture scores or protein solubility). There was a weak to modest relationship between the blood gas measurements and meat quality indicators. Blood pH (r = 0.566) and bicarbonate (r = 0.514) were positively correlated with subjective texture scores and a trend was seen for blood PCO2 and bicarbonate to be positively related to 45 min pH and subjective colour. These observations suggest that pigs with increased blood pH and bicarbonate may show an improvement in meat quality. Further research is necessary to find the optimum time and level of treatment to maximize the response.