Effects of Chromium Methionine and Zinc Source on Serum Metabolites, Endocrine Parameters, and the Antioxidant Status of Growing-Finishing Pigs

The objective of this study was to evaluate the effect of chromium methionine (CrMet) in combination with different zinc sources [zinc sulfate (ZnS) vs. zinc amino acid complex (ZnAA)] on serum metabolites, endocrine parameters, and antioxidant status of growing-finishing pigs. One hundred eighty crossbred pigs (Duroc × Landrace × Yorkshire; 32.02 ± 1.71 kg BW) were used in a completely randomized design with 3 dietary treatments. Each treatment had 10 replicates (5 pens each of barrows or gilts) with 6 pigs per replicate. Treatment diets were corn-soybean meal diets, formulated using NRC (1998) requirements. The 3 treatments were: 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. The experiment lasted 105 days until pigs reached approximately 110 kg BW. On the morning of day 106, after 16 h fasting, one pig nearest the mean body weight from each pen was bled. Blood samples were obtained from the anterior vena cava and serum was collected. Concentration of serum glucose in pigs fed CrMet-ZnS or CrMet-ZnAA was decreased compared with pigs fed CON (5.21, 5.18, and 5.82 mmol/L, respectively; P < 0.05). Concentration of total protein, triglycerides, serum urea nitrogen, high density lipoprotein, low density lipoprotein, and very low density lipoprotein were similar (P > 0.05) among treatments. Insulin was higher (15.2 vs. 13.7 μIU/mL, respectively; P < 0.05) and glucagon was lower (89.4 vs. 106.6 pg/mL, respectively; P < 0.05) in serum of pigs fed CrMet-ZnAA compared with pigs fed CON. Cortisol levels were decreased (115.4, 113.4, and 124.7 ng/mL, respectively; P < 0.05) in pigs fed CrMet-ZnS or CrMet-ZnAA compared to pigs fed CON. Growth hormone and insulin like growth factor-I were not affected (P > 0.05) by treatments. There was an increase (7.0 vs. 6.5 U/mL and 68.1 vs. 62.5 U/mL, respectively; P < 0.05) in total antioxidant capacity and Cu/Zn superoxide dismutase activity, while conversely there was a decrease (5.3 vs. 5.9 nmol/mL, respectively; P < 0.05) in malondialdehyde in serum of pigs fed CrMet-ZnAA compared with pigs fed CON. Catalase and glutathione peroxidase were similar (P > 0.05) among treatments. In conclusion, the supplementation of CrMet alone or in combination with ZnAA positively affected glucose metabolism, decreased the stress hormone cortisol, and improved serum antioxidant status of growing-finishing pigs.