Evaluation of various inclusion rates of organic zinc either as polysaccharide or proteinate complex on the growth performance, plasma, and excretion of nursery pigs

Three experiments were conducted to evaluate the effects of feeding dietary concentrations of organic Zn as a Zn-polysaccharide (Quali Tech Inc., Chaska, MN) or as a Zn-proteinate (Alltech Inc., Nicholasville, KY) on growth performance, plasma concentrations, and excretion in nursery pigs compared with pigs fed 2,000 ppm inorganic Zn as ZnO. Experiments 1 and 2 were growth experiments, and Exp. 3 was a balance experiment, and they used 306, 98, and 20 crossbred pigs, respectively. Initially, pigs averaged 17 d of age and 5.2 kg BW in Exp. 1 and 2, and 31 d of age and 11.2 kg BW in Exp. 3. The basal diets for Exp. 1, 2, and 3 contained 165 ppm supplemental Zn as ZnSO4 (as-fed basis), which was supplied from the premix. In Exp. 1, the Phase 1 (d 1 to 14) basal diet was supplemented with 0, 125, 250, 375, or 500 ppm Zn as Zn-polysaccharide (as-fed basis) or 2,000 ppm Zn as ZnO (as-fed basis). All pigs were then fed the same Phase 2 (d 15 to 28) and Phase 3 (d 29 to 42) diets. In Exp. 2, both the Phase 1 and 2 basal diets were supplemented with 0, 50, 100, 200, 400, or 800 ppm Zn as Zn-proteinate (as-fed basis) or 2,000 ppm Zn as ZnO (as-fed basis). For the 28-d Exp. 3, the Phase 2 basal diet was supplemented with 0, 200, or 400 ppm Zn as Zn-proteinate, or 2,000 ppm Zn as ZnO (as-fed basis). All diets were fed in meal form. In Exp. 1, 2, and 3, pigs were bled on d 14, 28, or 27, respectively, to determine plasma Zn and Cu concentrations. For all three experiments, there were no overall treatment differences in ADG, ADFI, or G:F (P = 0.15, 0.22, and 0.45, respectively). However, during wk 1 of Exp. 1, pigs fed 2,000 ppm Zn as ZnO had greater (P < or = 0.05) ADG and G:F than pigs fed the basal diet. In all experiments, pigs fed a diet containing 2,000 ppm Zn as ZnO had higher plasma Zn concentrations (P < 0.10) than pigs fed the basal diet. In Exp. 1 and 3, pigs fed 2,000 ppm Zn as ZnO had higher fecal Zn concentrations (P < 0.01) than pigs fed the other dietary Zn treatments. In conclusion, organic Zn either as a polysaccharide or a proteinate had no effect on growth performance at lower inclusion rates; however, feeding lower concentrations of organic Zn greatly decreased the amount of Zn excreted.     

Early- and traditionally weaned nursery pigs benefit from phase-feeding pharmacological concentrations of zinc oxide: effect on metallothionein and mineral concentrations.

Benefits of feeding pharmacological concentrations of zinc (Zn) provided by Zn oxide (ZnO) to 21-d conventionally weaned pigs in the nursery have been documented; however, several management questions remain. We conducted two experiments to evaluate the effect on growth from feeding 3,000 ppm Zn as ZnO during different weeks of the nursery period. In Exp. 1 (n = 138, 11.5 d of age, 3.8 kg BW) and Exp. 2 (n = 246, 24.5 d of age, 7.2 kg BW), pigs were fed either basal diets containing 100 ppm supplemental Zn (adequate) or the same diet with an additional 3,000 ppm Zn (high) supplied as ZnO. Pigs were fed four or two dietary phases in Exp. 1 and 2, respectively, that changed in dietary ingredients and nutrient content (lysine and crude protein) to meet the changing physiological needs of the pigs for the 28-d nursery period. Dietary Zn treatments were 1) adequate Zn fed wk 1 to 4, 2) high Zn fed wk 1, 3) high Zn fed wk 2, 4) high Zn fed wk 1 and 2, 5) high Zn fed wk 2 and 3, and 6) high Zn fed wk 1 to 4. In Exp. 1 and 2, pigs fed high Zn for wk 1 and 2 or the entire 28-d nursery period had the greatest (P < .05) ADG. During any week, pigs fed high Zn had greater concentrations of hepatic metallothionein and Zn in plasma, liver, and kidney than those pigs fed adequate Zn (P < .05). In summary, both early- and traditionally weaned pigs need to be fed pharmacological concentrations of Zn provided as ZnO for a minimum of 2 wk immediately after weaning to enhance growth.     

Effects of supplemental dietary phytase and pharmacological concentrations of zinc on growth performance and tissue zinc concentrations of weanling pigs

Three experiments were conducted to determine the effects of phytase, excess Zn, or their combination in diets for nursery pigs. In all experiments, treatments were replicated with five to seven pens of six to seven pigs per pen, dietary Ca and available P (aP) levels were decreased by 0.1% when phytase was added to the diets, excess Zn was added as ZnO, a basal level of 127 mg/kg of Zn (Zn sulfate) was present in all diets, and the experimental periods were 19 to 21 d. In Exp. 1, pigs (5.7 kg and 18 d of age) were fed two levels of phytase (0 or 500 phytase units/kg) and three levels of excess Zn (0, 1,000, or 2,000 ppm) in a 2 x 3 factorial arrangement. Added Zn linearly increased ADG and ADFI during Phase 1 (P = 0.01 to 0.06), Phase 2 (P = 0.02 to 0.09), and overall (P = 0.01 to 0.02). Gain:feed was linearly increased by Zn during Phase 1 (P = 0.01) but not at other times. Dietary phytase decreased ADG in pigs fed 1,000 or 2,000 ppm Zn during Phase 2 (Zn linear x phytase interaction; P = 0.10), did not affect (P = 0.27 to 0.62) ADFI during any period, and decreased G:F during Phase 2 (P = 0.01) and for the overall (P = 0.07) period. Plasma Zn was increased by supplemental Zn (Zn quadratic, P = 0.01) but not affected (P = 0.70) by phytase addition. In Exp. 2, pigs (5.2 kg and 18 d of age) were fed two levels of phytase (0 or 500 phytase units/kg) and two levels of Zn (0 or 2,000 ppm) in a 2 x 2 factorial arrangement. Supplemental Zn increased ADG and G:F during Phase 2 (P = 0.02 to 0.09) and overall (P = 0.07 to 0.08), but it had no effect (P = 0.11 to 0.89) on ADG during Phase 1 or ADFI during any period. Phytase supplementation increased ADG (P = 0.06) and G:F (P = 0.01) during Phase 2. Gain:feed was greatest for pigs fed 2,000 ppm Zn and phytase (Zn x phytase interaction; P = 0.01). Bone (d 20) and plasma Zn (d 7 and 20) were increased (P = 0.01) by added Zn but not affected (P = 0.51 to 0.90) by phytase. In Exp. 3, pigs (5.7 kg and 19 d of age) were fed a basal diet or the basal diet with Ca and aP levels decreased by 0.10% and these two diets with or without 500 phytase units/kg. Supplemental phytase had no effect (P = 0.21 to 0.81) on growth performance. Reduction of dietary Ca and aP decreased (P = 0.02 to 0.08) ADG, ADFI, and G:F for the overall data. These results indicate that excess dietary supplemental Zn increases ADG and plasma and bone Zn concentrations. Dietary phytase did not affect plasma or bone Zn concentrations.     

Effect of phosphorylated mannans and pharmacological additions of zinc oxide on growth and immunocompetence of weanling pigs

Three experiments were conducted to evaluate the efficacy of phosphorylated mannans (MAN) and pharmacological levels of ZnO on performance and immunity when added to nursery pig diets. Pigs (216 in each experiment), averaging 19 d of age and 6.2, 4.6, and 5.6 kg of BW in Exp. 1, 2, and 3, respectively, were blocked by BW in each experiment, and penned in groups of six. A lymphocyte blastogenesis assay was performed in each experiment to measure in vitro lymphocyte proliferation response. In Exp. 1, diets were arranged as a 2 x 2 factorial with two levels of Zn (200 and 2,500 ppm) and two levels of MAN (0 and 0.3% from d 0 to 10, and 0 and 0.2% from d 10 to 38). Zinc oxide increased (P < 0.05) ADG, ADFI, and G:F from d 0 to 10, and ADG and ADFI from d 10 to 24. In Exp. 2, diets were arranged as a 2 x 3 factorial with two levels of Zn (200 and 2,500 ppm) and three levels of MAN (0, 0.2, and 0.3%). Pigs fed 2,500 ppm Zn from d 0 to 10 had greater (P < 0.05) ADG, ADFI, and G:F than pigs fed 200 ppm Zn. From d 10 to 24, ADG was similar when pigs were fed 200 ppm Zn, regardless of MAN supplementation; however, ADG increased (P < 0.05) when 0.2% MAN was added to dietscontaining 2,500 ppm Zn (MAN x Zn interaction, P < 0.05). In Exp. 3, diets were arranged as a 2 x 3 factorial with two levels of MAN (0 and 0.3%) and three levels of Zn (200, 500, and 2,500 ppm). Zinc was maintained at 200 ppm from d 21 to 35, so only two dietary treatments (0 and 0.3% MAN) were fed during this period. Average daily gain was greater (P < 0.05) from d 7 to 21 when pigs were fed 2,500 ppm Zn compared with pigs fed 200 or 500 ppm Zn. The addition of MAN improved (P < 0.05) G:F from d 7 to 21 and d 0 to 35. Lymphocyte proliferation of unstimulated cells and phytohemagglutinin-stimulated cells was decreased (P < 0.05) in cells isolated from pigs fed MAN compared with cells isolated from pigs fed diets without MAN. Lymphocyte proliferation of pokeweed mitogen-stimulated cells isolated from pigs fed MAN was less (P < 0.05) than for pigs fed diets devoid of MAN when diets contained 200 ppm Zn; however, MAN had no effect on lymphocyte proliferation when the diet contained 500 or 2,500 ppm Zn (MAN x Zn interaction, P < 0.05). Although the magnitude of response to MAN was not equivalent to that of pharmacological concentrations of Zn, MAN mayimprove growth response when pharmacological Zn levels are restricted.     

Comparison of growth performance and zinc absorption, retention, and excretion in weanling pigs fed diets supplemented with zinc-polysaccharide or zinc oxide

Fifty weanling crossbred pigs averaging 6.2 kg of initial BW and 21 d of age were used in a 5-wk experiment to evaluate lower dietary concentrations of an organic source of Zn as a Zn-polysaccharide (Zn-PS) compared with 2,000 ppm of inorganic Zn as ZnO, with growth performance, plasma concentrations of Zn and Cu, and Zn and Cu balance as the criteria. The pigs were fed individually in metabolism crates, and Zn and Cu balance were measured on individual pigs (10 replications per treatment) from d 22 to 26. The basal Phase 1 (d 0 to 14) and Phase 2 (d 14 to 35) diets contained 125 or 100 ppm added Zn as Zn sulfate, respectively, and met all nutrient requirements. Treatments were the basal Phase 1 and 2 diets supplemented with 0, 150, 300, or 450 ppm of Zn as Zn-PS or 2,000 ppm Zn as ZnO. Blood samples were collected from all pigs on d 7, 14, and 28. For pigs fed increasing Zn as Zn-PS, there were no linear or quadratic responses (P > or = 0.16) in ADG, ADFI, or G:F for Phases 1 or 2 or overall. For single degree of freedom treatment comparisons, Phase 1 ADG and G:F were greater (P < or = 0.05) for pigs fed 2,000 ppm Zn as ZnO than for pigs fed the control diet or the diet containing 150 ppm Zn as Zn-PS. For Phase 2 and overall, ADG and G:F for pigs fed the diets containing 300 or 450 ppm of Zn as Zn-PS did not differ (P > or = 0.29) from pigs fed the diet containing ZnO. Pigs fed the diet containing ZnO also had a greater Phase 2 (P < or = 0.10) and overall (P < or = 0.05) ADG and G:F than pigs fed the control diet. There were no differences (P > or = 0.46) in ADFI for any planned comparison. There were linear increases (P < 0.001) in the Zn excreted (mg/d) with increasing dietary Zn-PS. Pigs fed the diet containing ZnO absorbed, retained, and excreted more Zn (P < 0.001) than pigs fed the control diet or any of the diets containing Zn-PS. In conclusion, Phase 2 and overall growth performance by pigs fed diets containing 300 or 450 ppm Zn as Zn-PS did not differ from that of pigs fed 2,000 ppm Zn as ZnO; however, feeding 300 ppm Zn as Zn-PS decreased Zn excretion by 76% compared with feeding 2,000 ppm Zn as ZnO.     

Effects of replacing pharmacological levels of dietary zinc oxide with lower dietary levels of various organic zinc sources for weanling pigs

Two 28-d randomized complete block design experiments were conducted to evaluate the effects of concentrations and sources of Zn on growth performance of nursery pigs. Seven stations participated in Exp. 1, which evaluated the efficacy of replacing 2,500 ppm of Zn from ZnO with 125, 250, or 500 ppm of Zn from Zn methionine. A control diet with 125 ppm of supplemental Zn was included at all stations. A total of 615 pigs were used in 26 replicates. Average weaning age was 20.6 d and the average initial BW was 6.3 kg. There were no differences in any growth response among the three supplemental Zn methionine levels fed in Exp. 1. Zinc supplementation from Zn methionine improved ADG compared with the control during all phases (P < 0.05), due primarily to an increase in ADFI. Pigs fed 2,500 ppm of Zn from ZnO gained faster (P < 0.01) than those fed the control diet during all phases, and faster (P < 0.05) than those fed supplemental Zn from Zn methionine for the 28-d experiment. Differences in gain were again due mainly to differences in feed intake. A second experiment compared five sources of supplemental organic Zn (500 ppm of Zn) with 500 and 2,000 ppm supplemental Zn from ZnO and a control (140 ppm total Zn). Six stations used a total of 624 pigs, with an average weaning age of 20.4 d and averaging 6.2 kg BW in 15 replicates. Pigs fed 2,000 ppm of Zn from ZnO gained faster (P < 0.05) than pigs fed the control or any of the 500 ppm of Zn treatments (ZnO or organic Zn). Pigs fed the 2,000 ppm of Zn from ZnO also consumed more feed than those receiving 500 ppm of Zn from ZnO or from any of the organic Zn sources (P < 0.05). Organic sources of Zn did not improve gain, feed intake, or feed efficiency beyond that achieved with the control diet. Supplemental Zn at a concentration of 500 ppm, whether in the form of the oxide or in an organic form, was not as efficacious for improved ADG as 2,000 to 2,500 ppm of Zn from ZnO.     

Effects of copper sulfate, tri-basic copper chloride, and zinc oxide on weanling pig performance

Three experiments were conducted to evaluate the effects of increasing dietary Cu and Zn on weanling pig performance. Diets were fed in 2 phases: phase 1 from d 0 to 14 postweaning and phase 2 from d 14 to 28 in Exp. 1 and 2 and d 14 to 42 in Exp. 3. The trace mineral premix, included in all diets, provided 165 mg/kg of Zn from ZnSO(4) and 16.5 mg/kg of Cu from CuSO(4). In Exp. 1, treatments were arranged in a 2 × 3 factorial with main effects of added Cu from tri-basic copper chloride (TBCC; 0 or 150 mg/kg) and added Zn from ZnO (0, 1,500, or 3,000 mg/kg from d 0 to 14 and 0, 1,000, or 2,000 mg/kg from d 14 to 28). No Cu × Zn interactions were observed (P > 0.10). Adding TBCC or Zn increased (P < 0.05) ADG and ADFI during each phase. In Exp. 2, treatments were arranged in a 2 × 3 factorial with main effects of added Zn from ZnO (0 or 3,000 mg/kg from d 0 to 14 and 0 or 2,000 mg/kg from d 14 to 28) and Cu (control, 125 mg/kg of Cu from TBCC, or 125 mg/kg of Cu from CuSO(4)). No Cu × Zn interactions (P > 0.10) were observed for any performance data. Adding ZnO improved (P < 0.02) ADG and ADFI from d 0 to 14 and overall. From d 0 to 28, supplementing CuSO(4) increased (P < 0.02) ADG, ADFI, and G:F, and TBCC improved (P = 0.006) ADG. In Exp. 3, the 6 dietary treatments were arranged in a 2 × 2 factorial with main effects of added Cu from CuSO(4) (0 or 125 mg/kg) and added Zn from ZnO (0 or 3,000 mg/kg from d 0 to 14 and 0 or 2,000 mg/kg from d 14 to 42). The final 2 treatments were feeding added ZnO alone or in combination with CuSO(4) from d 0 to 14 and adding CuSO(4) from d 14 to 42. Adding ZnO increased (P < 0.04) ADG, ADFI, and G:F from d 0 to 14 and ADG from d 0 to 42. Dietary CuSO(4) increased (P < 0.004) ADG and ADFI from d 14 to 42 and d 0 to 42. From d 28 to 42, a trend for a Cu × Zn interaction was observed (P = 0.06) for ADG. This interaction was reflective of the numeric decrease in ADG for pigs when Cu and Zn were used in combination compared with each used alone. Also, numerical advantages were observed when supplementing Zn from d 0 to 14 and Cu from d 14 to 42 compared with all other Cu and Zn regimens. These 3 experiments show the advantages of including both Cu and Zn in the diet for 28 d postweaning; however, as evident in Exp. 3, when 3,000 mg/kg of Zn was added early and 125 mg/kg of Cu was added late, performance was similar or numerically greater than when both were used for 42 d.     

Effects of dietary zinc and iron supplementation on mineral excretion, body composition, and mineral status of nursery pigs

Two experiments were conducted to evaluate the effects of dietary Zn and Fe supplementation on mineral excretion, body composition, and mineral status of nursery pigs. In Exp. 1 (n = 24; 6.5 kg; 16 to 20 d of age) and 2 (n = 24; 7.2 kg; 19 to 21 d of age), littermate crossbred barrows were weaned and allotted randomly by BW, within litter, to dietary treatments and housed individually in stainless steel pens. In Exp. 1, Phases 1 (d 0 to 7) and 2 (d 7 to 14) diets (as-fed basis) were: 1) NC (negative control, no added Zn source); 2) ZnO (NC + 2,000 mg/kg as Zn oxide); and 3) ZnM (NC + 2,000 mg/kg as Zn Met). In Exp. 2, diets for each phase (Phase 1 = d 0 to 7; Phase 2 = d 7 to 21; Phase 3 = d 21 to 35) were the basal diet supplemented with 0, 25, 50, 100, and 150 mg/kg Fe (as-fed basis) as ferrous sulfate. Orts, feces, and urine were collected daily in Exp. 1; whereas pigs had a 4-d adjustment period followed by a 3-d total collection period (Period 1 = d 5 to 7; Period 2 = d 12 to 14; Period 3 = d 26 to 28) during each phase in Exp. 2. Blood samples were obtained from pigs on d 0, 7, and 14 in Exp. 1 and d 0, 7, 21, and 35 in Exp. 2 to determine hemoglobin (Hb), hematocrit (Hct), and plasma Cu, (PCu), Fe (PFe), and Zn (PZn). Pigs in Exp. 1 were killed at d 14 (mean BW = 8.7 kg) to determine whole-body, liver, and kidney mineral concentrations. There were no differences in growth performance in Exp. 1 or 2. In Exp. 1, pigs fed ZnO or ZnM diets had greater (P < 0.001) dietary Zn intake during the 14-d study and greater fecal Zn excretion during Phase 2 compared with pigs fed the NC diet. Pigs fed 2,000 mg/kg, regardless of Zn source, had greater (P < 0.010) PZn on d 7 and 14 than pigs fed the NC diet. Whole-body Zn, liver Fe and Zn, and kidney Cu concentrations were greater (P < 0.010), whereas kidney Fe and Zn concentrations were less (P < 0.010) in pigs fed pharmacological Zn diets than pigs fed the NC diet. In Exp. 2, dietary Fe supplementation tended to increase (linear, P = 0.075) dietary DMI, resulting in a linear increase (P < 0.050) in dietary Fe, Cu, Mg, Mn, P, and Zn intake. Subsequently, a linear increase (P < 0.010) in fecal Fe and Zn excretion was observed. Increasing dietary Fe resulted in a linear increase in Hb, Hct, and PFe on d 21 (P < 0.050) and 35 (P < 0.010). Results suggest that dietary Zn or Fe additions increase mineral status of nursery pigs. Once tissue mineral stores are loaded, dietary minerals in excess of the body's requirement are excreted.     

Effect of mannan oligosaccharides on growth performance of weanling pigs

Four experiments were conducted to evaluate the effects of mannan oligosaccharides (provided by Bio-Mos [BM], a product containing a minimum of 28% glucomannoprotein from S. cerevisiae) on growth performance of nursery pigs. Treatments were replicated with five to six pens of four to five pigs each. Initial BW ranged from 4.7 to 5.4 kg, and pigs were weaned at 16 to 20 d of age. Experiments 1, 2, and 4 consisted of Phase 1 (7 to 8 d), Phase 2 (12 to 14 d), and Phase 3 (7 to 8 d) periods, but Exp. 3 consisted only of Phase 1 (7 d) and 2 (14 d) periods. The diets for Phase 1, 2, and 3 contained 1.6, 1.5, and 1.1% Lys, respectively. The treatments in Exp. 1 were 0, 0.20, and 0.30% BM, which did not affect growth performance. The treatments in Exp. 2 were two levels of excess Zn (0 and 3,000 ppm) and three levels of BM (0, 0.20, and 0.30%) in a 2 x 3 factorial. Excess Zn increased (P < 0.08) ADG and ADFI in Phase 2 and 3 and overall. The 0.20% BM addition increased ADG (Phase 3 and overall) and ADFI (Phase 2 and overall) in the absence of excess Zn but did not affect or decreased these response variables in the presence of excess Zn (Zn x BM quadratic, P < 0.08). Experiment 3 was similar to Exp. 2, but the 0.30% BM addition was not used. Excess Zn decreased (P < 0.09) ADG in Phase 1 but increased (P < 0.09) ADG and ADFI in Phase 2. The BM decreased (P < 0.03) overall ADFI but increased Phase 2 and overall ADG and gain:feed (GF) in the absence of excess Zn but not in the presence of excess Zn (Zn x BM, P < 0.07). The BM decreased ADFI during Phase 2, but the decrease was greater in pigs fed excess Zn (Zn x BM, P < 0.07). Experiment 4 evaluated the interactive effects of the antibiotic (oxytetracycline and neomycin) and BM and of Zn and BM. Antibiotic (no excess Zn) increased (P < 0.01) ADG and ADFI in Phases 2 and 3 and overall. The BM addition decreased ADG and GF in Phase 2 when the antibiotic was not in the diet but increased ADG when the antibiotic was in the diet (antibiotic x BM, P < 0.05). Excess Zn increased (P < 0.07) ADG and ADFI during Phases 2 and 3 and overall. In Phase 2, the 0.20% BM decreased GF when excess Zn was not added to the diet but increased GF when Zn was included (Zn x BM, P < 0.03). Mannan oligosaccharides improved pig performance in some instances during Phase 2 when fed in combination with an antibiotic and no excess dietary Zn, but it had no effect or negative effects in the presence of excess Zn or in the absence of an antibiotic.     

Effect of pharmacological concentrations of zinc oxide with or without the inclusion of an antibacterial agent on nursery pig performance

A study involving nine research stations from the NCR-42 Swine Nutrition Committee used a total of 1,978 crossbred pigs to evaluate the effects of dietary ZnO concentrations with or without an antibacterial agent on postweaning pig performance. In Exp. 1, seven stations (IA, MI, MN, MO, NE, ND, and OH) evaluated the efficacy of ZnO when fed to nursery pigs at 0, 500, 1,000, 2,000, or 3,000 mg Zn/kg for a 28-d postweaning period. A randomized complete block experiment was conducted in 24 replicates using a total of 1,060 pigs. Pigs were bled at the 28-d period and plasma was analyzed for Zn and Cu. Because two stations weaned pigs at < 15 d (six replicates) and five stations at > 20 d (18 replicates) of age, the two sets of data were analyzed separately. The early-weaned pig group had greater (P < 0.05) gains, feed intakes, and gain:feed ratios for the 28-d postweaning period as dietary ZnO concentration increased. Later-weaned pigs also had increased (P < 0.01) gains and feed intakes as the dietary ZnO concentration increased. Responses for both weanling pig groups seemed to reach a plateau at 2,000 mg Zn/kg. Plasma Zn concentrations quadratically increased (P < 0.01) and plasma Cu concentrations quadratically decreased (P < 0.01) when ZnO concentrations were > 1,000 mg Zn/kg. Experiment 2 was conducted at seven stations (KY, MI, MO, NE, ND, OH, and OK) and evaluated the efficacy of an antibacterial agent (carbadox) in combination with added ZnO. The experiment was a 2 x 3 factorial arrangement in a randomized complete block design conducted in a total of 20 replicates. Carbadox was added at 0 or 55 mg/kg diet, and ZnO was added at 0, 1,500, or 3,000 mg Zn/ kg. A total of 918 pigs were weaned at an average 19.7 d of age. For the 28-d postweaning period, gains (P < 0.01), feed intakes (P < 0.05), and gain:feed ratios (P < 0.05) increased when dietary ZnO concentrations increased and when carbadox was added. These responses occurred in an additive manner. The results of these studies suggest that supplemental ZnO at 1,500 to 2,000 mg Zn/kg Zn improved postweaning pig performance, and its combination with an antibacterial agent resulted in additional performance improvements.     

Effects of water and diet acidification with and without antibiotics on weanling pig growth and microbial shedding

Two 5-wk experiments were conducted to determine the effects of water and diet acidification with and without antibiotics on weanling pig growth performance and microbial shedding. In Exp. 1, 204 pigs (19.2 d of age) were used in a 3 x 2 factorial, with 3 dietary treatments fed with or without water acidification (2.58 mL/L of a propionic acid blend; KEM SAN, Kemin Americas, Des Moines, IA). Dietary treatments were: 1) control, 2) control + 55 ppm of carbadox (CB), and 3) dietary acid [DA; control + 0.4% organic acid-based blend (fumaric, lactate, citric, propionic, and benzoic acids; Kemin Americas)] on d 0 to 7 followed by 0.2% inorganic acid-based blend (phosphoric, fumaric, lactic, and citric acids; Kemin Americas) on d 7 to 34. In Exp. 2, 210 pigs (average 18.3 d of age) were fed 1 of 3 dietary treatments: 1) control, 2) control + 55 ppm of CB, and 3) control + 38.6 ppm of tiamulin + 441 ppm of chlortetracycline on d 0 to 7 followed by 110 ppm of chlortetracycline on d 7 to 35 (TC) with or without dietary acidification (same as Exp. 1) in a 3 x 2 factorial arrangement of treatments. For both experiments, the pigs were allotted based on genetics, sex, and initial BW [5.5 kg (Exp. 1) or 5.6 kg (Exp. 2)]. Pigs were housed at 6 or 7 (Exp. 1) and 7 (Exp. 2) pigs/pen. Treatments were fed in 3 phases: d 0 to 7, 7 to 21, and 21 to 35 (34 d, Exp. 1). Fecal grab samples were collected from 3 pigs/pen on d 6, 20, and 33 for measurement of pH and Escherichia coli. During phase 3 and overall in Exp. 1, pigs fed CB had greater (P < 0.001) ADG (overall ADG, 389 vs. 348, and 348 g/d, respectively), ADFI (P < 0.007, 608 vs. 559, and 554 g/d, respectively), and d 34 BW (P < 0.001, 18.8 vs. 17.3, and 17.3 kg, respectively) than pigs fed NC and DA. Phase 3 ADG was improved (P < 0.01) by water acidification across all diets. In Exp. 2, pigs fed CB and TC had greater ADG (P < 0.004; 315 and 303 vs. 270 g/d, respectively), ADFI (P < 0.01), and d 35 BW (P < 0.002; 16.7 and 16.2 vs. 15.1 kg, respectively) than pigs fed NC. There was a tendency (P < 0.08) for an improvement in ADG when DA was added to the NC or TC, but decreased ADG when DA was added to CB.     

Additivity of effects from dietary copper and zinc on growth performance and fecal microbiota of pigs after weaning

Four experiments were conducted to determine the interactive effects of pharmacological amounts of Zn from ZnO and Cu from organic (Cu-AA complex; Cu-AA) or inorganic (CuSO(4)) sources on growth performance of weanling pigs. The Cu was fed for 4 (Exp. 1) or 6 (Exp. 2, 3, and 4) wk after weaning, and Zn was fed for 4 (Exp. 1) or 2 (Exp. 2, 3, and 4) wk after weaning. Treatments were replicated with 7 pens of 5 or 6 pigs per pen (19.0 ± 1.4 d of age and 5.8 ± 0.4 kg of BW, Exp. 1), 12 pens of 21 pigs per pen (about 21 d of age and 5.3 kg of BW, Exp. 2), 5 pens of 4 pigs per pen (20.3 ± 0.5 d of age and 7.0 ± 0.5 kg of BW, Exp. 3), and 16 pens of 21 pigs per pen (about 21 d of age and 5.7 kg of BW, Exp. 4). In Exp. 1 and 2, Cu-AA (0 vs. 100 mg/kg of Cu) and ZnO (0 vs. 3,000 mg/kg of Zn) were used in a 2 × 2 factorial arrangement. Only Exp. 1 used in-feed antibiotic (165 mg of oxytetracycline and 116 mg of neomycin per kilogram feed), and Exp. 2 was conducted at a commercial farm. In Exp. 3, sources of Cu (none; CuSO(4) at 250 mg/kg of Cu; and Cu-AA at 100 mg/kg of Cu) and ZnO (0 vs. 3,000 mg/kg of Zn) were used in a 3 × 2 factorial arrangement. In Exp. 4, treatments were no additional Cu, CuSO(4) at 315 mg/kg of Cu, or Cu-AA at 100 mg/kg of Cu to a diet supplemented with 3,000 mg/kg of Zn from ZnO and in-feed antibiotic (55 mg of carbadox per kilogram of feed). In Exp. 1 and 2, both Zn and Cu-AA improved (P < 0.001 to P = 0.03) ADG and ADFI. No interactions were observed, except in wk 1 of Exp. 2, where Zn increased the G:F only in the absence of Cu-AA (Cu-AA × Zn, P = 0.04). A naturally occurring colibacillosis diarrhea outbreak occurred during this experiment. The ZnO addition reduced (P < 0.001) the number of pigs removed and pig-days on antibiotic therapy. In Exp 3, ADFI in wk 2 was improved by Zn and Cu (P < 0.001 and P = 0.09, respectively) with no interactions. In wk 1, G:F was reduced by ZnO only in the absence of Cu (Cu × Zn, P = 0.03). Feeding Zn decreased fecal microbiota diversity in the presence of CuSO(4) but increased it in the presence of Cu-AA (Cu source × Zn, P = 0.06). In Exp. 4, Cu supplementation improved the overall ADG (P = 0.002) and G:F (P < 0.001). The CuSO(4) effect on G:F was greater (P < 0.001) than the Cu-AA effect. Our results indicate that pharmacological amounts of ZnO and Cu (Cu-AA or CuSO(4)) are additive in promoting growth of pigs after weaning.     

Effect of dietary copper source (cupric citrate and cupric sulfate) and concentration on growth performance and fecal copper excretion in weanling pigs

In each of two experiments, 924 pigs (4.99 kg BW; 16 to 18 d of age) were assigned to 1 of 42 pens based on BW and gender. Pens were allotted randomly to dietary copper (Cu) treatments that consisted of control (10 ppm Cu as cupric sulfate, CuSO4 x 5H2O) and supplemental dietary Cu concentrations of 15, 31, 62, or 125 ppm as cupric citrate (CuCit), or 62 (Exp. 2 only), 125 (Exp. 1 only), or 250 ppm as CuSO4. Live animal performance was determined at the end of the 45-d nursery phase in each experiment. On d 40 of Exp. 2, blood and fecal samples were collected from two randomly selected pigs per pen for evaluation of plasma and fecal Cu concentrations and fecal odor characteristics. In Exp. 1, ADG, ADFI, and G:F were increased (P < 0.05), relative to controls, when pigs were fed diets containing 250 ppm Cu as CuSO4. Pigs fed diets containing 125 ppm Cu as CuCit had increased (P < 0.05) ADG compared with pigs fed diets supplemented with 15 or 62 ppm Cu as CuCit. The ADG, ADFI, and G:F did not differ among pigs fed diets containing 125 and 250 ppm Cu as CuSO4 or 125 ppm Cu as CuCit. In Exp. 2, pigs fed diets containing 250 ppm Cu as CuSO4 had improved (P < 0.05) ADG, ADFI, and G:F compared with controls. In addition, ADG, ADFI, and G:F were similar when pigs were fed diets containing either 250 ppm Cu as CuSO4 or 125 ppm Cu as CuCit. Pigs fed diets containing 62 ppm Cu as CuSO4 or CuCit had similar ADG, ADFI, and G:F. Plasma Cu concentrations were not affected by dietary Cu source or concentration, but fecal Cu concentrations were increased (P < 0.05) as the dietary concentration of Cu increased. Pigs consuming diets supplemented with 125 ppm Cu as CuCit had fecal Cu concentrations that were lower (P < 0.05) than pigs consuming diets supplemented with 250 ppm Cu as CuSO4. Fecal Cu did not differ in pigs receiving diets supplemented with 62 ppm Cu as CuSO4 or CuCit. Odor characteristics of feces were not affected by Cu supplementation or source. These data indicate that 125 and 250 ppm Cu gave similar responses in growth, and that CuCit and CuSO4 were equally effective at stimulating growth and improving G:F in weanling pigs. Fecal Cu excretion was decreased when 125 ppm Cu as CuCit was fed compared with 250 ppm Cu as CuSO4. Therefore, 125 ppm of dietary Cu, regardless of source, may provide an effective environmental alternative to 250 ppm Cu as CuSO4 in weanling pigs.     

Effects of organic forms of zinc on growth performance,tissue zinc distribution,and immune response of weanling pigs

This study was conducted to determine the effect of zinc level and source on growth performance, tissue Zn concentrations, intracellular distribution of Zn, and immune response in weanling pigs. Ninety-six 3-wk-old crossbred weanling pigs (BW = 6.45 +/- 0.17 kg) were assigned to one of six dietary treatments (four pigs per pen, four replicates per treatment) based on weight and litter origin. Treatments consisted of the following: 1) a corn-soybean meal-whey diet (1.2% lysine) with a basal level of 80 ppm of supplemental Zn from ZnSO4 (control; contained 104 ppm total Zn); 2) control + 80 ppm added Zn from ZnSO4; 3) control + 80 ppm added Zn from Zn methionine (ZnMet); 4) control + 80 ppm added Zn from Zn lysine (ZnLys); 5) control + 40 ppm added Zn from ZnMet and 40 ppm added Zn from ZnLys (ZnML); and 6) control + 160 ppm added Zn from ZnSO4. Zinc supplementation of the control diet had no effect on ADG or ADFI. Gain efficiency was less (P < 0.05) for pigs fed 80 ppm of Zn from ZnSO4 than for control pigs and pigs fed 160 ppm of Zn from ZnSO4. Organ weights, Zn concentration, and intracellular distribution of Zn in the liver, pancreas, and spleen were not affected (P = 0.12) by Zn level or source. Skin thickness response to phytohemagglutinin (PHA) was not affected (P = 0.53) by dietary treatment. Lymphocyte proliferation in response to PHA was greater (P < 0.05) in pigs fed ZnLys than in pigs fed the control diet or the ZnML diet; however, when pokeweed mitogen was used, lymphocyte proliferation was greatest (P < 0.05) in pigs fed the ZnMet diet than pigs fed the control, ZnLys, ZnML, or 160 ppm ZnSO4 diets. Antibody response to sheep red blood cells was not affected by dietary treatments. Supplementation of 80 ppm of Zn from ZnSO4 or ZnMet and 160 ppm of Zn from ZnSO4 decreased (P < 0.05) the antibody response to ovalbumin on d 7 compared with control pigs, but not on d 14. Phagocytic capability of peritoneal exudate cells was increased (P < 0.05) when 160 ppm of Zn from ZnSO4 was supplemented to the diet. The number of red blood cells ingested per phagocytic cell was increased (P < 0.05) in pigs fed the diet supplemented with a combination of ZnMet and ZnLys and the diet with 160 ppm of Zn from ZnSO4. Results suggest that the level of Zn recommended by NRC for weanling pigs was sufficient for optimal growth performance and immune responses, although macrophage function may be enhanced at greater levels of Zn. Source of Zn did not alter these measurements.     

Effect of microbial phytase addition with or without the trace mineral premix in nursery, growing, and finishing pig diets

Two experiments were conducted to determine the interactive effects of phytase with and without a trace mineral premix (TMP) in diets for nursery, growing, and finishing pigs on growth performance, bone responses, and tissue mineral concentrations. Pigs (initial and final BW of 5.5 and 111.6 kg [Exp. 1] or 5.4 and 22.6 kg [Exp. 2]) were allotted to treatments on the basis of BW with eight (Exp. 1) or six (Exp. 2) replications of six or seven pigs per replicate pen. Pigs were started on the diets the day of weaning (average of 18 d). In both experiments, the treatments were with or without 500 phytase units/kg of diet and with or without the TMP in a 2 x 2 factorial arrangement. The Ca and available P concentrations were decreased by 0.10% in diets with phytase. The nursery phase consisted of Phase I (7 d), Phase II (14 d), and Phase III (13 d) periods. In Exp. 1, 26 of 52 pigs fed the diet without the TMP and without phytase had severe skin lesions and decreased growth performance; therefore, pigs fed this diet were switched to the positive control diet. In Exp. 2, the treatment without the TMP and without phytase had 12 replications instead of six. At the end of Phase III, half these replications were switched to the positive control diet and half were switched to the diet without the TMP but with phytase. In Exp. 1 during Phases II and III and in the overall data, pigs fed the diet without the TMP had decreased ADG and ADFI, but the addition of phytase prevented these responses (phytase x TMP; P < 0.02). Growth performance was not affected by diet during the growing-finishing period. Coccygeal bone Zn and Na concentrations were decreased (P < 0.09) in pigs fed the diet without the TMP, and adding phytase increased (P < 0.03) Zn and Fe concentrations. In Exp. 2 during Phases I and II, pigs fed the diet without the TMP had decreased ADG, but the addition of phytase prevented this response (phytase x TMP; P < 0.10). Pigs fed the diet without the TMP had decreased (P < 0.10) ADG (Phase II and overall), ADFI (Phases II and III and in the overall data), and G:F (Phase III). Coccygeal bone Zn and Cu concentrations were decreased (P < 0.09) in pigs fed the diet without the TMP, and adding phytase increased (P < 0.03) Zn concentration in the bones. These data indicate that removing the TMP in diets for nursery pigs decreases growth performance and bone mineral content, and that phytase addition to the diet without the TMP prevented the decreased growth performance.     

Growth-promoting efficacy in young pigs of two sources of zinc oxide having either a high or a low bioavailability of zinc

Commercial sources of zinc oxide (ZnO) differ widely in Zn relative bioavailability (RBV), but it is unknown whether growth-promoting efficacy in young pigs is influenced by RBV of the ZnO sources used. We compared a low-RBV (39%) ZnO manufactured by the Waelz process (W) to a high-RBV (93%) ZnO manufactured by the hydrosulfide process (HS). Antibacterial agents were included in the diet in only one of the four trials (Exp. 4). In Exp. 1, pigs (n = 36, 6.5 kg, 28 d of age) were randomly assigned in three replicates to receive 0, 1,500, or 3,000 mg Zn/kg from HS Zn in a 21-d growth assay. Growth rates and feed intake responded linearly (P < 0.01) to incremental doses of Zn. In Exp. 2, pigs (n = 60, 6.1 kg, 28 d of age) were randomly assigned in five replicates to receive either 0 or 1,500 mg W or HS Zn/kg during a 21-d feeding period. Growth performance was improved (P < 0.01) by the addition of ZnO. During wk 1, however, pigs receiving HS Zn grew faster (P < 0.03) than those receiving W Zn, but the difference diminished to a trend (P < 0.08) during wk 2. Morphology of duodenal, jejunal, and ileal intestinal sections was examined at d 21 of the assay, but neither source of ZnO had an effect on crypt depth or on villus height or width. In Exp. 3, weaned pigs (n = 48, 5.4 kg, 21 d of age) were randomly assigned in four replicates to the same dietary treatments as in Exp. 2 for a 17-d growth assay. Growth performance was improved (P < 0.05) by the addition of ZnO, but no difference was detected between the two sources. In Exp. 4, pigs (n = 60, 6.2 kg, 28 d of age) were randomly assigned in five replicates to receive either 0 or 1,500 mg/kg W or HS Zn in an 11-d growth assay wherein antimicrobial agents were included in the basal diet. Growth rates during the first 6-d were improved (P < 0.06) by the addition of ZnO, with a trend (P < 0.10) for greater weight gain in pigs receiving HS than in those fed W Zn. During the entire 11-d, however, there was no difference in growth rates between pigs fed the two sources of ZnO. In conclusion, RBV of Zn in ZnO did not substantially affect the growth-promoting efficacy of ZnO in young pigs fed diets with or without antimicrobial agents.     

Growth and intestinal morphology of pigs from sows fed two zinc sources during gestation and lactation

An experiment was conducted to compare the effects of organic (Zn AA complex, ZnAA) and inorganic Zn (ZnSO4) sources on sows and their progeny during gestation and lactation and on the pigs during the nursery period. The dietary treatments were 1) a corn-soybean meal diet with 100 ppm Zn from ZnSO4 (control); 2) diet 1 + 100 ppm additional Zn from ZnSO4; and 3) diet 1 + 100 ppm additional Zn from ZnAA. Dietary additions were on an as-fed basis. Thirty-one primaparous and multiparous sows were allotted to the treatment diet beginning on d 15 of gestation and continuing through lactation. At weaning (d 17 of age), 202 pigs (63, 55, and 84 pigs for treatments 1 to 3, respectively) were allotted to the same dietary treatment as their dam. The pigs were fed a 3-phase diet regimen during the nursery period: d 0 to 7 (phase I); d 7 to 21 (phase II); and d 21 to 28 (phase III). At weaning and at the end of phase III, 1 gilt per replicate was killed, and the left front foot, liver, pancreas, and entire small intestine were removed. Diet had no effect (P > 0.10) on any response during gestation. During lactation, there was an increase (P < 0.10) in litter birth weight in sows fed ZnAA compared with those fed the control or ZnSO4 diets. The sows fed ZnAA nursed more pigs (P < 0.10) than sows fed the ZnSO4 diet, and they weaned more pigs (P < 0.05) than sows fed the control diet. Jejunal villus height of the weaned pigs from sows fed ZnSO4 was increased (P < 0.05) compared with those from the sows fed the control diet. During the nursery period, growth performance was not affected (P > 0.10) by diet. Pigs fed ZnSO4 had greater duodenal villus width (P < 0.05) than those fed ZnAA, and pigs fed ZnSO4 or the control diet had greater ileal villus width (P < 0.05) than those fed ZnAA. Pigs fed ZnSO4 or ZnAA had more (P < 0.05) bone Zn than those fed the control diet. Liver Zn concentration was greatest in pigs fed ZnSO4, followed by those fed ZnAA, and then by those fed the control diet (P < 0.05). Pancreas Zn was increased (P < 0.05) in pigs fed ZnSO4 compared with those fed the control diet. These results suggest that 100 ppm Zn in trace mineral premixes provides adequate Zn for optimal growth performance of nursery pigs, but that 100 ppm additional Zn from ZnAA in sow diets may increase pigs born and weaned per litter.     

Effects of increasing dietary L-carnitine on growth performance of weanling pigs

Four experiments were conducted to evaluate the effects of supplementing graded levels (0 to 100 ppm) of L-carnitine to the diet of weanling pigs on growth performance during a 34- to 38-d experimental period. A fifth experiment was conducted to determine the effects of addition of L-carnitine to diets with or without added soybean oil (SBO) on growth performance. In Exp. 1, 128 pigs (initial BW = 5.5 kg) were allotted to four dietary treatments (six pens per treatment of four to six pigs per pen). Dietary treatments were a control diet containing no added L-carnitine and the control diet with 25, 50, or 100 ppm of added L-carnitine. In Exp. 2, 3, and 4, pigs (4.8 to 5.6 kg of BW) were allotted to five dietary treatments consisting of either a control diet containing no added L-carnitine or the control diet with 25, 50, 75, or 100 ppm of added L-carnitine. All diets in Exp. 1 to 4 contained added soybean oil (4 to 6%). There were seven pens per treatment (four to five pigs per pen) in Exp. 2, whereas Exp. 3 and 4 had five and six pens/treatment (eight pigs per pen), respectively. In general, dietary carnitine additions had only minor effects on growth performance during Phases 1 and 3; however, dietary L-carnitine increased (linear [Exp. 1], quadratic [Exp. 2 to 4], P < 0.03) ADG and gain:feed (G:F) during Phase 2. The improvements in growth performance during Phase 2 were of great enough magnitude that carnitine addition tended to increase ADG (linear, P < 0.10) and improve G:F (quadratic, P < 0.02) for the entire 38-d period. In Exp. 5, 216 weanling pigs (5.8 kg of BW) were allotted (12 pens/treatment of four to five pigs per pen) to four dietary treatments. The four dietary treatments were arranged in a 2 x 2 factorial with main effects of added SBO (0 or 5%) and added L-carnitine (0 or 50 ppm). Pigs fed SBO tended (P < 0.07) to grow more slowly and consumed less feed compared with those not fed SBO, but G:F was improved (P < 0.02). The addition of L-carnitine did not affect (P > 0.10) ADG or ADFI; however, it improved (P < 0.03) G:F. Also, the increase in G:F associated with L-carnitine tended to be more pronounced for pigs fed SBO than those not fed SBO (carnitine x SBO, P < 0.10). These results suggest that the addition of 50 to 100 ppm of added L-carnitine to the diet improved growth performance of weanling pigs. In addition, supplemental L-carnitine tended to be more effective when SBO was provided in the diet.     

Effects of feeding diets containing low crude protein and coarse wheat bran as alternatives to zinc oxide in nursery pig diets

Two experiments were conducted to determine the effects of crude protein (CP) level in diets containing coarse wheat bran (CWB) with or without pharmacological levels of Zn (provided by zinc oxide: ZnO) on growth performance and fecal DM of nursery pigs. In experiment 1, 360 barrows (Line 200 × 400, DNA, Columbus, NE, initially 5.6 kg) were allotted to 1 of 6 dietary treatments from d 0 to 21 after weaning with 5 pigs per pen and 12 pens per treatment. Treatments included a positive control diet (21% CP) with 3,000 mg/kg Zn in phase 1 and 2,000 mg/kg in phase 2; negative control (21% CP) with 110 mg/kg added Zn, and 4 diets containing 4% CWB and 110 mg/kg added Zn formulated to contain 21%, 19.5%, 18%, or 16.5% CP. The 2 control diets and 21% CP CWB diet contained 1.40% standardized ileal digestible (SID) Lys in phase 1 and 1.35% SID Lys in phase 2, while the 19.5%, 18%, and 16.5% CP diets contained 1.33, 1.25 and 1.20% Lys, respectively, in both phases. Pigs fed the positive control diet containing pharmacological ZnO had increased (P < 0.05) ADG and G:F compared with the negative control and the 21% CP CWB diet. Reducing CP (concurrently with SID Lys) in diets containing CWB decreased ADG and G:F (linear, P = 0.002); however, fecal DM increased (linear, P = 0.005). In experiment 2, two groups of 300 and 350 pigs, initially 7.0 and 6.2 kg, respectively, were used with 5 pigs per pen and 26 pens per treatment. The objective was to determine if adding back essential AA would improve growth performance of pigs fed the low CP diets. All dietary treatments were fed for 13 days, contained 4% CWB, and consisted of: (1) positive control with 2,000 mg/kg of Zn and 21% CP (1.35% SID Lys); (2) no ZnO and 21% CP; and 3 diets with no ZnO formulated to 18% CP and (3) 1.2% SID Lys; (4) 1.35% SID Lys by the addition of feed grade amino acids (AA), and (5) diet 4 with non-essential amino acids (NEAA; Gly and Glu). Pigs fed 21% CP with ZnO had increased (P = 0.001) ADG compared to those fed 18% CP (1.35% SID Lys) with high levels of feed grade amino acids or those fed the reduced SID Lys (1.2%) diet. Overall, G:F was improved (P < 0.001) for pigs fed 21% CP diets and those fed the 18% CP diet with NEAA compared to pigs fed 1.2% SID Lys and pigs fed high levels of feed grade amino acids. Fecal DM was increased for pigs fed the reduced SID Lys diet. In summary, pharmacological levels of Zn improve pig growth performance, but reducing CP (and subsequently SID Lys) decreased nursery pig growth performance.     

Effect of dietary mannan oligosaccharides and(or) pharmacological additions of copper sulfate on growth performance and immunocompetence of weanling and growing/finishing pigs

Two experiments were conducted to determine the efficacy of mannan oligosaccharides (MOS) fed at two levels of Cu on growth and feed efficiency of weanling and growing-finishing pigs, as well as the effect on the immunocompetence of weanling pigs. In Exp. 1, 216 barrows (6 kg of BW and 18 d of age) were penned in groups of six (9 pens/treatment). Dietary treatments were arranged as a 2 x 2 factorial consisting of two levels of Cu (basal level or 175 ppm supplemental Cu) with and without MOS (0.2%). Diets were fed from d 0 to 38 after weaning. Blood samples were obtained to determine lymphocyte proliferation in vitro. From d 0 to 10, ADG, ADFI, and gain:feed (G:F) increased when MOS was added to diets containing the basal level of Cu, but decreased when MOS was added to diets containing 175 ppm supplemental Cu (interaction, P < 0.01, P < 0.10, and P < 0.05, respectively). Pigs fed diets containing 175 ppm Cu from d 10 to 24 and d 24 to 38 had greater (P < 0.05) ADG and ADFI than those fed the basal level of Cu regardless of MOS addition. Pigs fed diets containing MOS from d 24 to 38 had greater ADG (P < 0.05) and G:F (P < 0.10) than those fed diets devoid of MOS. Lymphocyte proliferation was not altered by dietary treatment. In Exp. 2, 144 pigs were divided into six pigs/pen (six pens/treatment). Dietary treatments were fed throughout the starter (20 to 32 kg BW), grower (32 to 68 kg BW), and finisher (68 to 106 kg BW) phases. Diets consisted of two levels of Cu (basal level or basal diet + 175 ppm in starter and grower diets and 125 ppm in finisher diets) with and without MOS (0.2% in starter, 0.1% in grower, and 0.05% in finisher). Pigs fed supplemental Cu had greater (P < 0.05) ADG and G:F during the starter and grower phases compared to pigs fed the basal level of Cu. During the finisher phase, ADG increased when pigs were fed MOS in diets containing the basal level of Cu, but decreased when MOS was added to diets supplemented with 125 ppm Cu (interaction, P < 0.05). Results from this study indicate the response of weanling pigs fed MOS in phase 1 varied with level of dietary Cu. However, in phase 2 and phase 3, diets containing either MOS or 175 ppm Cu resulted in improved performance. Pharmacological Cu addition improved gain and efficiency during the starter and grower phases in growing-finishing pigs, while ADG response to the addition of MOS during the finisher phase seems to be dependent upon the level of Cu supplementation.