Effects of Chromium Methionine and Zinc Source on Performance, Carcass Traits, and Meat Quality of Growing-Finishing Pigs

The objectives of this study were to evaluate the effects of chromium methionine complex (CrMet) fed with ZnSO₄ (ZnS) or Zn amino acid complex (ZnAA) on performance and carcass quality of growing-finishing pigs. One hundred eighty crossbred pigs (Duroc x Landrace x Yorkshire; 32.0 ± 1.71 kg BW) were used in a completely randomized design with 3 treatments: 1) Control (CON): 100 mg/kg Zn from ZnSO₄; 2) CrMet-ZnS: CON + 0.2 mg/kg Cr from CrMet; or 3) CrMet-ZnAA: 50 mg/kg Zn from ZnSO₄ + 50 mg/kg Zn from ZnAA + 0.2 mg/kg Cr from CrMet. Each treatment had 10 replicates (5 pens each of barrows or gilts; 6 pigs/pen). Pigs were fed corn-soybean meal diets based on NRC (1998) requirements. The experiment lasted 105 d with 3 stages: Phase 1 (30 to 50 kg BW, 28 d), Phase 2 (50 to 80 kg BW, 42 d), and Phase 3 (80 to 110 kg BW, 35 d). At the end of the experiment, one pig from each pen with BW nearest the mean of the pen was selected for harvest. Average daily gain was similar (P > 0.05) among the 3 treatments in all 3 phases and for the entire experiment (overall average 0.74 kg/d). Average daily feed intake by pigs fed CrMet-ZnAA was lower (P < 0.05) compared to pigs fed CON for the entire experiment (2.30 vs. 2.42 kg/d). Gain:feed was improved (P < 0.05) in Phases 2 and 3 in pigs fed CrMet-ZnS or CrMet-ZnAA compared to pigs fed CON (0.324, 0.332, and 0.312, respectively for Phase 2 and 0.282, 0.293, 0.266, respectively for Phase 3) and for the entire experiment by pigs fed CrMet-ZnAA compared to pigs fed CON (0.326 vs. 0.301). Pigs fed CrMet-ZnAA had greater (P < 0.05) HCW, dressing percentage and LM area than pigs fed CON (83.2 vs. 80.5 kg, 76.0 vs. 73.5%, and 64.26 vs. 62.03 cm²). Pigs fed CON and CrMet-ZnS had similar (P > 0.05) HCW, dressing percentage and LM area. Color and drip loss of LM did not differ (P > 0.05) among treatments. The pH_24h of LM from pigs fed CrMet-ZnS and CrMet-ZnAA was greater (P < 0.05) compared to pigs fed CON (5.73 and 5.71 vs. 5.45). Results suggest that Cr from CrMet improved performance and carcass characteristics of growing-finishing pigs and Zn from ZnAA further enhanced the effects.