Effects of feeding modified tall oil and supplemental potassium and magnesium on growth performance, carcass characteristics, and meat quality of growing-finishing pigs

Eighty crossbred gifts (initially 45.9 kg) were allotted randomly to one of four dietary treatments by weight and ancestry. The trial was arranged as a 2 x 2 factorial with two levels of modified tall oil (MTO) (0 or 0.50%) a nd added K2SO4-2MgSO(4) (0 or 2%), equating to daily K and Mg intakes of 10 .84 and 7.75 g, respectively. The corn-soybean meal diets were fed in two p hases [45.9 to 76.2 and 76.2 to 118.1 kg body weight (BW)], and supplementa l K/Mg was added in place of corn for the final 7 d preslaughter (starting at 114.1 kg BW). Dietary treatment did not affect (P > 0.10) average daily gain (ADG), average daily feed intake (ADFI), or gain to feed ratio(G/F). F eeding MTO decreased average backfat (P = 0.05) and increased intramuscular marbling (P = 0.04). Modified tall oil increased (P = 0.02) percentage lea n, and K/Mg supplementation lowered (P = 0.04) longissimus muscle glycogen content. Dietary treatment did not affect (P > 0.10) other carcass characte ristics or measures of meat quality. Feeding MTO increased plasma glucose ( P = 0.05) and decreased (P = 0.10) base excess in the extracellular fluid. Feeding K/Mg decreased (P < 0.10) plasma pH, BUN, and base excess in the wh ole-blood and extracellular fluid and increased (P < 0.10) ionized Mg++ and lactate. These results support earlier research identifying MTO as a carca ss modifier and contributor to meat composition and quality. Potassium and Mg supplementation altered whole-blood profiles and longissimus muscle glyc ogen content in a manner expected to improve pork quality, although not obs erved.