Abstract
It is common to use 2500–3000 ppm Zn as ZnO to prevent post-weaning diarrhea. However, most of the dietary Zn supply is excreted, causing environmental accumulation, and recently antimicrobial resistance concerns have also increased. Phytate supplementation in most piglet diets may create insoluble salts with several divalent cations (Ca, P, Zn) inhibiting their absorption. Therefore, the objective of the present experiment was to observe the effect of the interaction between the use of therapeutic doses of Zn and phytase supplementation on growth performance in weanling piglets (0 to 35 d post-weaning). A total of 320 pigs were used in a 2 × 2 factorial arrangement, where the main factors were Zn inclusion (125 or 2500 ppm Zn) and phytase inclusion (0 and 1000 FTU). Piglets were reared in 32 pens (10 pigs/pen; 8 replicates per treatment). The pre-starter (0–14 d) and starter (14–35 d) diets contained 2520 and 2460 Kcal NE/kg, 19.65 and 19.00% CP, 1.25 and 1.23 digestible Lys, 0.35 and 0.77% Ca, and 0.33 and 0.25% P digestible, respectively. The pre-starter diet had low Ca levels (0.33%) without CaCO3. Feed intake and individual BW were registered on d 0, 14, and 35 post-weaning. Performance parameters were analyzed with ANOVA by using the Mixed procedure of the statistical package SAS. There was an effect of Zn on BW at d 14 and 35 (P < 0.05); where pigs with no ZnO addition presented higher weights compared to pigs with ZnO (11.12 and 21.84 vs. 10.56 and 20.76 Kg, respectively). There was no phytase effect on BW, ADG, ADFI, and FCR. However, there were significant interactions on BW at d 35, ADFI 0–14 and ADG 0–35 (P < 0.05), where piglets without ZnO and 1000 FTU of phytase obtained better results (higher BW, ADG, and ADFI) compared to piglets with ZnO and 1000 FTU of phytase (22.2 vs. 20.19 Kg; 327.13 vs. 261.13 g/d; and 416.76 vs. 357.34 g/d, respectively), suggesting that phytase does not have the same benefits with high levels of Zn on the diet. There was also a statistical trend for the interactions on BW14 (P = 0.08), ADG 0–14 (P = 0.07), ADG 14–35 (P = 0.06), and ADFI 0–35 (P = 0.06), following the same pattern. It can be concluded that diets without therapeutic ZnO and low levels of Ca but 1000 FTU of phytase allow better growth than diets with high Zn levels. Copyright © 2016. American Society of Animal Science .