Abstract
A total of 2,268 pigs (initially 5.7 ± 0.31 kg) were used to evaluate the effect of Zn source and level on nursery performance, fecal dry matter, and fecal Zn concentration. At weaning, pens of pigs were blocked by body weight (BW) and placement date and then randomly assigned to 1 of the 7 dietary treatments in a 3 × 2 + 1 factorial, with main effects of Zn source and level. Zinc sources included ZnO and two sources of Zn hydroxychloride (source A= Hydroxy Zn, SAM Nutrition, Bloomington, MN; source B= Intellibond Z, Selko, Indianapolis, IN) and dietary Zn concentrations included 1,500 or 1,000 mg/kg during phase 1 and 1,000 or 500 mg/kg during phase 2, respectively. An additional treatment was included as a positive control, with 3,000 and 2,000 ppm of Zn from ZnO in phases 1 (d 0 to 11) and 2 (d 11 to 25), respectively. After the experimental period (dietary phases 1 and 2), all pigs were fed a common phase 3 diet containing 100 ppm of added Zn from ZnSO(4) for 14 d. On d 7 and 21, fecal samples from 3 pigs per pen were collected for fecal dry matter and Zn analysis. During the experimental phase, common phase, and overall, no significant Zn source × level interactions or main effects of Zn source or level were observed. No linear or quadratic responses (P > 0.10) to ZnO level were observed for growth performance, mortality, removals, or fecal dry matter in any of the periods. For d-7 fecal Zn concentration, an interaction (P = 0.009) was observed between Zn source × level where a greater (P < 0.05) fecal Zn concentration was observed as the dietary Zn increased when ZnO or Zn hydroxychloride source B were used, but no differences (P > 0.10) between levels were observed for Zn hydroxychloride source A. At d 21, the fecal Zn concentration decreased (P < 0.001) as dietary Zn concentration decreased, independent of the Zn source. In conclusion, the source and level of dietary Zn did not significantly affect growth performance or fecal dry matter of nursery pigs. Feeding reduced levels of Zn from either ZnO or Zn hydroxychloride resulted in similar growth performance to pharmacological levels of ZnO. However, using lower dietary Zn levels independent of the source resulted in lower fecal Zn concentration.