Determination of the Efficacy of Titrated Levels of Water Soluble Zinc Amino Acid Complex on Growth Performance of Nursery Pigs

High dietary concentrations of zinc oxide and copper sulfate are used in weaned pig diets to improve growth performance and feed efficiency, but few studies have investigated the effects of supplementing zinc via water. To evaluate the efficacy of a water soluble zinc amino acid complex “Zinpro LQ” (Zinpro Corporation, Eden Prairie, MN), two hundred eighty crossbred pigs (5.6 kg BW; PIC 337) were randomly allotted to four water treatments (7 pens/treatment; 10 pigs/pen). The water treatments were 0, 20, 40 and 80 mg Zn/L of water. Pigs were fed a common diet with added Zn as ZnO or Cu as CuSO₄ during each dietary phase: Phase 1 (2,500 mg Zn/kg; from d 1-7), Phase 2 (1,750 mg Zn/kg; from d 7-14), Phase 3 (200 mg Cu/kg; from d 14-21), and Phase 4 (200 mg Cu/kg; from d 21-42). All diets were formulated based on corn and soybean meal with no added medications. Pigs and feeders were weighed weekly to determine ADG, ADFI, and G:F. Water meters were used to record and calculate average daily water intake (ADWI). Data were analyzed as a randomized complete block design. Orthogonal polynomial contrasts were used to determine linear, quadratic, and cubic effects. A linear increase (P < 0.01) in ADWI (ADWI = 0.0844*day + 0.2145; R² = 0.91) was observed for d 0-42. Throughout the experiment, there were no differences (P > 0.05) in ADFI (550, 550, 570, and 560 g/pig) and ADWI (3.93, 3.92, 3.86, and 4.21 L/pig) among treatments. Daily zinc intake increased with increasing zinc concentration (linear, P < 0.0001). During d 0-21, a linear trend (P < 0.10) was noted for increased ADG (250, 250, 260, and 280 g/pig) and d 21 BW (11.07, 11.21, 11.27, and 11.74 kg) with increased water zinc intake. Furthermore, increasing zinc intake via water improved (linear, P < 0.05) G:F from d 0-21 (0.79, 0.81, 0.83, and 0.84). For d 21-42, increasing zinc intake via water tended to improve ADG (quadratic, P = 0.10; 550, 560, 600, and 570 g/pig) and final BW (linear, P = 0.12; 21.99, 22.38, 23.30, and 23.30 kg), and improved G:F for the total experiment period (linear, P < 0.05; 0.77, 0.79, 0.82, and 0.83). In conclusion, supplementing drinking water of nursery pigs with Zinpro LQ resulted in linear improvements in ADG and G:F for the first 3 weeks post-weaning, and improved G:F for the entire nursery period.