200 Effects of zinc oxide removal and different nutritional plans on the growth performance, health, and behavior of nursery pigs from different genetic lines
Authors: Moita Vitor , Camp Jordi , Vier Carine M , Cast Wayne R , Dritz Steve , Zaragoza Luis E , Wilson-Wells Danielle , Lu Ning , Orlando Weasley A , Landero Jose , Young Malachy 
Published: May 2024

Abstract
This study was conducted to investigate the impacts of the removal of zinc oxide (ZnO) supplemented at pharmaceutical levels and different nutritional plans on the growth performance, health, and behavior of nursery pigs from different genetic sire lines. A total of 1,440 newly weaned barrows and gilts were housed into nursery pens with 30 pigs/pen (0.25m2/pig). Pigs were assigned to eight groups following a randomized complete block design arranged on a 2 x 2 x 2 factorial arrangement [Genetic sire line: PIC 337 or PIC 800; ZnO supplementation: 0 or 2,500 ppm; nutritional plan: Control (PIC recommendation) or Treatment (TRT)]. Pigs were fed in three dietary phases (P1:7 d; P2: 21 d; P3: 21 d). The nutrient levels of the TRT for each phase consisted of reduced crude protein (P1: 21 vs. 18.43%; P2: 20.80 vs. 18.73%), SID Lys (P1: 1.40 vs. 1.20%; P2: 0.35 vs. 1.20%), net energy (P1: 2,450 vs. 2,352 kcal/kg; P2: 2,450 vs. 2,377 kcal/kg) and lactose levels (P1: 15 vs. 7%; P2: 7 vs. 5%), and use of calcium formate instead of calcium carbonate for both P1 and P2, and pigs receiving the same diet in P3. Health and behavior were assessed through ear lesion (weekly during P3) and fecal (weekly during P1 and P2) scoring, mortality/removals, and medication control. Growth performance was assessed by individually weighing pigs and recording feed disappearance every week throughout the experimental period. Data were analyzed using a generalized linear model considering pen as the experimental unit. Models included treatments and their interactions as fixed effects, and block and pen within block as the random terms. Pigs fed ZnO showed greater (P &lt; 0.05) overall average daily gain (ADG; 495 vs. 456 g/d) and average daily feed intake (ADFI; 681 vs. 633 g/d); and decreased (P &lt; 0.05) diarrhea incidence (DI; 3.64 vs 10.21%) at d 14 after weaning and mortality/removals (2.31 vs. 5.11%) compared with pigs fed no ZnO. No significant differences were detected between the nutritional plans for performance traits (P &gt; 0.05); however, pigs fed the TRT had less (P &lt; 0.05) DI (7.54 vs. 11.43%) at d 7 after weaning than pigs fed the control nutrition plan. Regarding the genetic sire lines, PIC 337 pigs showed greater (P &lt; 0.05) overall body weight (26.1 vs. 25.4 kg), ADG (486 vs. 465 g/d) and ADFI (666 vs. 648 g/d); and decreased (P &lt; 0.05) mortality/removals (2.54 vs. 4.66%) and DI (6.92 vs. 12.41%) at d 7 after weaning compared with PIC 800 pigs. In summary, PIC 337 pigs fed ZnO under the control nutritional program showed greater growth performance during the nursery period. This study reaffirmed the benefits of ZnO fed to nursery pigs during the post-weaning period; however, since different countries are banning or reducing the use of ZnO, nutritional strategies should be considered to not negatively impact the health and subsequent performance of nursery pigs.