270 Zinc from Methionine Hydroxy Analog Chelate Is More Effective in Enriching Tissues Than Zinc from an Amino Acid Complex in Growing Pigs Using Stable Isotopes
Authors: Acosta Camargo Jesus A , Ren Ping , Provin Ashley , Rode Tracy , Tucker Heather A , Hancock Deana 
Published: November 2023

Abstract
An adequate supply of Zn should effectively reach tissues to support fundamental physiological functions. This study compared tissue enrichment using stable Zn isotopes when fed as methionine hydroxy analog chelate (Zn-MHAC [Novus International Inc., St. Charles, MO]) or an amino acid complex (Zn-AAC) in growing pigs. Twenty gilts (31.5 ± 2.8 kg BW) were individually housed and fed a common diet (corn-soy-based with phytase) with 26 mg/kg of Zn from ingredients and 15 mg/kg supplemented as Zn sulfate. At d 28, pigs were surgically catheterized in the jugular vein and moved to metabolism crates. After 2 d of recovery, 16 pigs were randomly selected to receive an oral bolus containing 1 of 2 doses (8 or 12 mg) of Zn67 in the form of Zn-AAC (8 or 12 mg) and Zn70 in the form of Zn-MHAC. The remaining 4 pigs received a placebo bolus and served as controls. Blood samples were collected periodically between -15 and 1,440 min relative to bolus. Total urine and fecal output were collected at 0, 6, 12, and 24 h relative to bolus. All pigs were euthanized 24 h after bolus to harvest tissues. Zinc isotope enrichment was calculated from analyzed samples as the difference of Zn67 and Zn70 portions between control and isotope-bolused pigs. Data were analyzed as a 2×2 factorial (mineral source×dose) using PROC MIXED procedure of SAS. No interactions between trace mineral source and isotope dose for any tested variables were observed. Gastrointestinal and central metabolism tissues, including stomach, duodenum, jejunum, ileum, pancreas, liver, and kidney, demonstrated greater enrichment from Zn-MHAC than Zn-AAC (P ≤ 0.001). In reproductive tissues, ovary showed similar Zn enrichment between Zn-MHAC and Zn-ACC (P = 0.841). However, there was greater enrichment from Zn-MHAC than Zn-AAC in the uterus (P = 0.002). For musculoskeletal tissues, despite a numerical increase for Zn-MHAC compared with Zn-AAC, there was no significant difference of Zn source on enrichment of metacarpal bones (P = 0.190). The hoof matrix tended to have greater enrichment from Zn-MHAC than Zn-AAC (P = 0.097). There were no differences between trace mineral sources on enrichment of Zn in the muscle (P = 0.839). Immune tissues, including thymus (P &lt; 0.001) and spleen (P = 0.017), demonstrated greater enrichment from Zn-MHAC than Zn-AAC. Despite a numerical increase with Zn-MHAC, plasma area under the curve (AUC) was not significantly different between Zn-MHAC and Zn-AAC (P = 0.467). Similarly, despite a numerical increase, the higher dose of Zn isotope did not significantly increase (P &gt; 0.050) enrichment in gastrointestinal, central metabolic, reproductive, musculoskeletal (except for muscle: P = 0.042), immune tissues, or plasma AUC. There were no differences in Zn AUC (0-24h; P &gt; 0.100) enrichment between trace mineral source and dose in feces and urine. In conclusion, Zn-MHAC delivered more Zn to physiologically important tissues that support productivity and health of pigs than Zn-AAC.