Effects of dietary magnesium and halothane genotype on performance and carcass traits of growing-finishing swine

Halothane-negative (NN) and halothane-carrier (Nn) pigs were assigned randomly to one of three dietary treatments: (1) control com-soybean meal diets; (2) control diets supplemented with 1.25% magnesium mica (MM); or (3) control diets supplemented with 2.5% MM. When the lightest block averaged 108.8 kg, pigs were harvested at a commercial pork slaughter plant, and bone-in pork loins were captured, vacuum-packaged and transported back for measurement of pork quality traits. The NN pigs had greater average daily gain (ADG) during the grower (P < 0.05) and finisher (P < 0.05) periods than Nn pigs. Although MM had no effect (P > 0.10) on ADG, pigs fed 1.25% MM had a higher (P < 0.05) gain-to-feed ratio (G:F) during the grower phase than pigs fed 2.5% MM; whereas, pigs fed control diets had an intermediate G:F. Carcasses from Nn pigs were leaner (P < 0.05) and heavier (P < 0.05) muscled than carcasses from NN pigs. In contrast, a greater (P < 0.05) percentage of carcasses from Nn pigs received color scores characteristic of the pale, soft and exudative (PSE) condition. Although there were distinct genotype effects on performance and carcass traits, long-term supplementation of diets with MM had no beneficial, or deleterious, effects on pork quality or carcass yield. (C) 2002 Elsevier Science B.V. All rights reserved.