195. Methionine Hydroxy Analogue Bis-chelated Trace Minerals Differentially Impact Barrows and Gilts Compared with Inorganic Trace Minerals.

Abstract Trace mineral source influences nutrient utilization and growth performance in swine. Methionine hydroxy analogue chelated trace minerals (MHAC; Mintrex® Trace Minerals; Novus International, Chesterfield, MO) may provide greater bioavailability than inorganic trace minerals (ITM), potentially improving performance at lower dietary inclusion levels. This study evaluated the effects of a complete MHAC trace mineral program on growth performance of grow–finish pigs and assessed potential sex-specific responses. A total of 80 pigs (TN70 × TN Duroc; 40 barrows and 40 gilts) were used in a randomized block design. Following a common nursery program (100 mg/kg Zn from ZnSO4, 80 mg/kg Cu from CuSO4, and 50 mg/kg Mn from MnO), pigs were assigned at 69 d of age to 1 of 2 dietary treatments during the grow–finish phase: 1) ITM (100 mg/kg Zn from ZnO, 20 mg/kg Cu from CuSO4, and 25 mg/kg Mn from MnO) or 2) MHAC supplying Zn, Cu, and Mn at reduced levels of 40, 10, and 20 mg/kg, respectively. The methionine contribution from MHAC was accounted for in diet formulation. Pigs were housed in pens equipped with automated feeders to record individual feed intake and feeding behavior. Growth performance was evaluated throughout the grow–finish period and analyzed using mixed models with treatment, sex, time, and their interactions as fixed effects and pig as a random effect (PROC MIXED, SAS 9.4). Overall growth performance differed between sexes. Barrows had greater average daily feed intake (ADFI) than gilts (2.589 vs. 2.092 kg; P < 0.001) and a lower gain-to-feed ratio (0.389 vs. 0.445; P = 0.008). Despite reduced trace mineral inclusion, pigs fed MHAC had similar ADFI compared with ITM (2.388 vs. 2.293 kg; P = 0.344). Gain-to-feed ratio was not different between treatments (0.419 vs. 0.409 for MHAC and ITM, respectively; P = 0.619). A significant trace mineral program × sex interaction was observed for average daily gain (ADG; P = 0.003) and final body weight (BW; P = 0.026). Barrows fed MHAC had greater ADG compared with those fed ITM (1.068 vs. 0.964 kg; P < 0.001), whereas gilts showed similar ADG between treatments (0.939 vs. 0.929 kg). Likewise, final BW was greater in MHAC barrows compared with ITM (127.9 vs. 119.2 kg; P = 0.026), while gilts showed only a numerical difference (116.6 vs. 115.9 kg). These results indicate that replacing inorganic trace minerals with lower allowance levels of MHAC trace minerals can improve growth performance of finishing pigs. Although both sexes benefited from MHAC supplementation, the magnitude of response was greater in barrows than in gilts, suggesting sex-related differences in nutrient utilization that may influence trace mineral allowance strategies.