Effects of dietary zinc source and concentration on performance of growing-finishing pigs reared with reduced floor space

The objectives of this experiment were to evaluate effects of dietary zinc source (AA complex vs. inorganic) and increasing zinc concentration on growth performance and carcass composition of growing-finishing pigs housed in crowded conditions. Maternal-line barrows and gilts (636 pigs; initial BW = 28.7 kg) were blocked by initial BW and assigned randomly within block to 1 of 5 treatments. Twelve pens were assigned to each treatment over 3 replicate trials. Treatments were (1) control (Con9)—pigs housed in an uncrowded environment (0.73 m²/pig) and fed diets based on corn, soybean meal, and dried distillers grains with solubles containing 60 mg/kg Zn (phases 1, 2, and 3), and 50 mg/kg Zn (phase 4); (2) crowded (Con11)—pigs housed at 0.60 m²/pig and fed the same diets as Con9; (3) ZnAA40—same as Con11 + 40 mg/kg Zn from Zn AA complex (Availa-Zn, Zinpro Corp., Eden Prairie, MN); (4) ZnAA80—same as Con11 + 80 mg/kg Zn from Zn AA complex; and (5) inorganic zinc (ZnSO80)—same as Con11 + 80 mg/kg Zn from zinc sulfate monohydrate. Growth characteristics were determined at the end of each dietary phase (28 d). Upon completion of the trial, carcass composition and meat quality were recorded. Overall, crowding decreased ADG (P < 0.05, SE = 0.01) for Con11 compared with Con9 pigs (0.91 vs. 0.97 kg). There were no differences in average daily feed intake (2.74, 2.66, 2.62, 2.59, and 2.65 kg; SE = 0.05) or G:F (0.368, 0.356, 0.369, 0.368, and 0.365; SE = 0.006) among Con9, Con11, ZnAA40, ZnAA80, and ZnSO80, respectively. Neither zinc source nor concentration affected fat-free lean percentage, DP, loin muscle area, or backfat depth. Altogether, these data indicate that neither additional AA complexed zinc nor additional inorganic zinc influenced growth performance, carcass composition, or pork quality of pigs housed under crowded conditions.