Evaluating the NRC levels of Cu, Fe, Mn, and Zn using organic and inorganic mineral sources for grower-finisher swine.

The dietary effects of Cu, Fe, Mn, and Zn levels, and the addition of Zn and Fe to a nonfortified, micromineral basal diet were evaluated in grower-finisher pigs. Growth, feed efficiency, hematology, carcass characteristics, and loin quality were assessed in growing-finishing pigs (n = 222; initial BW = 24 kg). Corn-soybean meal diets fortified with limestone and dicalcium phosphate with added phytase constituted the basal diets. A study was conducted with 6 dietary treatments and 7 replicates in a randomized complete block design. Treatments consisted of: 1) basal diet without added Cu, Fe, Mn, and Zn microminerals, 2) basal + 50% NRC Cu, Fe, Mn, and Zn requirements, 3) basal + 100% NRC Cu, Fe, Mn, and Zn requirements, 4) basal + 25 mg Zn/kg, 5) basal + 50 mg Zn/kg, and 6) basal + 50 mg Fe/kg. The microminerals were added as an organic mineral proteinate and all diets incorporated organic Se at 0.3 mg/kg. Diets were fed ad libitum over 3 growth phases. At 55, 80, and 115 kg BW, 3 pigs per pen were bled and hemoglobin (Hb) and percent hematocrit (Hct) were determined. At 115 kg BW, 3 pigs per pen were killed and carcass characteristics and loin quality measurements were determined. The ADG, ADFI, and G:F for each of the 3 dietary phases and overall period were not affected by dietary micromineral treatments. The concentration of Hb and percent Hct did not differ because of the treatment at each of the 3 phases. There were no treatment differences in carcass characteristics (HCW, backfat, or LM area). Loin pH, color (L*, a*, and b*), and drip loss did not differ by dietary treatment. Subjective marbling, color, and firmness scores, and intramuscular fat content of loins did not differ as the micromineral level increased above the 1998 and 2012 NRC requirements. The LM from pigs fed supplemental Fe had greater (P < 0.05) firmness and wetness scores than pigs fed the basal diet. These results indicate that there is sufficient amount of innate microminerals (Cu, Fe, Mn, and Zn) in a typical corn-soybean meal based diet to meet the grower-finisher pig's requirement for growth and hematological measurements. Although there was no detrimental effect by eliminating these microminerals from diets, it would seem that a dietary level of 50% of the NRC requirement for Cu, Fe, Mn, and Zn would be warranted.