Effect of weaning and in-feed high doses of zinc oxide on zinc levels in different body compartments of piglets

The Mechanism of Zinc Oxide in Alleviating Diarrhea in Piglets after Weaning: A Review from the Perspective of Intestinal Barrier Function

Weaning is one of the most challenging phases for piglets, and it is also the time when piglets are the most susceptible to diarrhea, which may result in significant economic losses for pig production. One of the dietary strategies for reducing post-weaning diarrhea (PWD) in piglets is to provide them with a pharmacological dose of zinc oxide (ZnO). However, excessive or long-term usage of high-dose ZnO has significant impacts on pig health and the ecological environment. Therefore, caution should be exercised when considering the use of high-dose ZnO for the prevention or treatment of PWD in piglets. In this paper, the significant role of zinc in animal health, the potential mode of action of ZnO in alleviating diarrhea, and the impact of innovative, highly efficient ZnO alternatives on the regulation of piglet diarrhea were reviewed to offer insights into the application of novel ZnO in pig production.

Combination of Hydrolysable Tannins and Zinc Oxide on Enterocyte Functionality: In Vitro Insights

The management of gastrointestinal disease in animals represents a significant challenge in veterinary and zootechnic practice. Traditionally, acute symptoms have been treated with antibiotics and high doses of zinc oxide (ZnO). However, concerns have been raised regarding the potential for microbial resistance and ecological detriment due to the excessive application of this compound. These concerns highlight the urgency of minimizing the use of ZnO and exploring sustainable nutritional solutions. Hydrolysable tannins (HTs), which are known for their role in traditional medicine for acute gastrointestinal issues, have emerged as a promising alternative. This study examined the combined effect of food-grade HTs and subtherapeutic ZnO concentration on relevant biological functions of Caco-2 cells, a widely used model of the intestinal epithelial barrier. We found that, when used together, ZnO and HTs (ZnO/HTs) enhanced tissue repair and improved epithelial barrier function, normalizing the expression and functional organization of tight junction proteins. Finally, the ZnO/HTs combination strengthened enterocytes' defense against oxidative stress induced by inflammation stimuli. In conclusion, combining ZnO and HTs may offer a suitable and practical approach for decreasing ZnO levels in veterinary nutritional applications.

Exploring zinc deficiency using serum Zn levels: consequences and potential solutions in suckling pigs

Three trials were undertaken to provide an answer to different questions: 1) Are suckling pigs able to maintain physiological serum Zn levels throughout lactation and do these levels vary between high and low body weight (BW) pigs?, 2) Are serum Zn levels in pigs soon after weaning a predisposing factor for diarrhea?, and 3) Is it possible to increase serum Zn levels at weaning by supplementing Zn during lactation. In trial 1, blood samples were taken from pigs during lactation. Eight pigs (one piglet per litter) had blood drawn on days 0 (farrowing), 7, 14, 21, and 28 (weaning), and 60 pigs (selected from the whole farrowing batch with 35 sows), categorized as either heavy (8.63 kg) or light (5.50 kg) had blood drawn on day 28. Serum Zn levels at birth were 1.2 mg/L and decreased (P < 0.01) to 0.67 mg/L on day 28. Heavier pigs showed greater (P < 0.01) serum Zn levels (0.98 mg/L) than light BW pigs (0.79 mg/L). In trial 2, blood samples were obtained from 240 pigs at weaning (26.2 ± 2.5 d) with an average initial BW of 6.94 ± 1.87 kg and were distributed into 24 pens (10 pigs/pen) by BW. Diarrhea incidence was recorded daily from days 0 to 35 post-weaning. From the 240 pigs, a group of 110 pigs with uniform BW (6.5 ± 1.9 kg) was selected and separated into two groups based on serum Zn levels at weaning with 55 pigs with low serum Zn (LZn: <0.71 mg/L) and 55 pigs with high serum Zn (HZn: >0.9 mg/L). Pigs with LZn were 2.49 times as likely to have diarrhea as pigs with HZn (P < 0.02). In trial 3, a total of 96 suckling pigs were allotted four treatments that consisted of the daily administration of 0, 6, 18, or 30 mg of Zn as Zn citrate in capsule form during the last 7 d of lactation. Pigs were individually weighed, and blood samples were obtained on days 14, 21 (weaning), and 7 after weaning. Serum Zn levels linearly increased by day as Zn citrate supplementation increased (interaction, P < 0.001). However, only light pigs supplemented with 18 and 30 mg/L of Zn experienced an increase in serum Zn levels during lactation. In conclusion, a decrease in serum Zn levels occurs during lactation and is more severe in low BW pigs. Low Zn status (< 0.7 mg/L) at weaning may be a predisposing factor for diarrhea. However, Zn supplementation during lactation can mitigate this decrease in light pigs.

Analysis of heavy metals in the conversion of lake sediment and restaurant waste by black soldier fly (Hermetia illucens)

The risk posed by heavy metals makes it difficult to dispose of sediment contaminants from dredging lakes in China. Black soldier fly (Hermetia illucens) can convert organic waste, such as restaurant waste and lake sediment, to high-value-added protein feed and fertilizer. Experimental groups were formed in this study to explore the conversion of heavy metals present in the mixture of restaurant waste and lake sediment by black soldier fly larvae (BSFL). The results demonstrated that BSFL could survive in pure sediment with an 84.76% survival rate. Relative to the substrate, BSFL could accumulate 70-90% zinc (Zn), chromium (Cr), copper (Cu), and 20-40% cadmium (Cd) and lead (Pb). The experimental group 2:3, with 40% lake sediment and 60% restaurant waste, was the best group after conversion for 15 days, which showed a 95.24% survival rate of BFSL, 82.20 mg average weight of BFSL, 8.92 mm average length of BFSL, with varying content of heavy metals such as Cu (43.22 mg/kg), Zn (193.31 mg/kg), Cd (1.58 mg/kg), Cr (25.30 mg/kg) Cr, and Pb (38.59 mg/kg) in BSFL. Furthermore, the conversion residue conforms to the relevant standards of organic fertilizer in China and can be used as organic fertilizer. Overall, the present study shows that black soldier flies can improve the resource utilization of lake sediment, especially by reducing the effect of heavy metals.

Effects of dietary zinc/copper ratios on the metabolism of zinc and copper in weaned pigs

This study compared the effects of different dietary zinc/copper ratios on zinc (Zn) and copper (Cu) metabolism in weaned pigs. One hundred and sixty piglets (7.81 ± 0.25 kg; 21 d of age) were used in a completely randomized 2 × 2 factorial design composed with high (H) and low (L) levels of added dietary Zn (100 and 3,000 mg/kg) and dietary Cu (6 and 130 mg/kg). Piglets were slaughtered at 21, 28, 35, and 42 d of age for blood and tissues collection. Serum, jejunum mucosa, liver, and kidney concentrations of Zn and Cu were analyzed as well as tissues mRNA abundance of genes related to their metabolism. Serum and liver Zn concentrations increased at days 28, 35, and 42 in HZn groups compared to pre-treatment levels (day 21; P ≤ 0.01) but for LZn animals, values decreased at days 28, 35, and 42 in liver (P ≤ 0.01) but remained stable vs. day 21 levels in serum (P ≥ 0.37). Serum, jejunum mucosa, liver, and kidney Zn concentrations were greater in HZn groups from day 28 (P ≤ 0.01). In jejunum mucosa, the mRNA expression of ZIP4 was lower in HZn piglets at day 28 (P ≤ 0.01) and at day 42 whereas HCu supplementation increased ZIP4 expression in LZn but not in HZn diets (P = 0.05). For ZNT1, MT3, and MT1, values of relative mRNA expression were greater for HZn animals in jejunum mucosa, liver, and kidney (P ≤ 0.01) from day 28. In kidney (P < 0.01) at day 42, HZn supplementation increased MTs expression in both LCu or HCu groups. Serum and liver Cu concentrations decreased at days 35 and 42 in all treatments compared to day 21 (P ≤ 0.04), except LZnHCu in liver that was not different from day 21 (P ≥ 0.17). Serum Cu concentrations were lower in HZn and greater in HCu groups at days 35 and 42 (P ≤ 0.01) whereas hepatic Cu was reduced by HZn diets in both LCu and HCu groups at days 35 and 42 (P ≤ 0.01). Jejunum Cu concentrations were increased by HCu diets in HZn but not in LZn groups at days 28 and 42 (P ≤ 0.04). Renal Cu concentrations were greater in HZn groups at day 28 (P < 0.01) whereas at day 42 HZn diets increased Cu values in both LCu and HCu groups (P ≤ 0.01). The expression of ATP7A in kidney at day 42 was greater for HZn groups (P = 0.02). In conclusion, high dietary Zn levels were not efficiently regulated by homeostatic mechanisms and significantly impaired Cu homeostasis. Low dietary Zn/Cu ratios allow a more efficient regulation of the metabolism of these trace minerals in post-weaning piglets. The current official recommendations for Zn and Cu to post-weaning piglets apparently do not fulfill their requirements.

Using Shotgun Sequencing to Describe the Changes Induced by In-Feed Zinc Oxide and Apramycin in the Microbiomes of Pigs One Week Postweaning

Postweaning diarrhea (PWD) is a relevant problem associated with early weaning on pig farms. For decades, in-feed antibiotics and therapeutic zinc oxide (ZnO) have been widely used to prevent PWD in piglets. The European Union is banning both strategies in 2022 due to antimicrobial resistance and environmental contamination concerns, respectively. Understanding the effects of these products on the pig microbiome is crucial for correcting potential microbial disbalances that would prompt PWD. Using shotgun sequencing, three trials were carried out to explore the impact of in-feed apramycin and ZnO, combined with different farm hygiene protocols, on the fecal microbiomes of piglets 7 days postweaning. In trial 1, 28-day-old piglets were allocated to one of three groups: control diet (Ct), Ct + ZnO (Zn), and Ct + apramycin (Ab). In trials 2 and 3, piglets were allocated to the same treatments, but the trials also included different cleaning protocols, achieving different hygiene levels. In-feed treatments impacted the richness, diversity, and relative abundance of the piglets' microbiome more than hygiene. Pigs in the Ct group showed higher species richness than pigs in the Ab and Zn groups. A clustering analysis evidenced a link between Enterobacteriaceae in the Ct group; Lactobacillaceae and Veillonellaceae mainly in the Ct group; and Bacteroidaceae, Ruminococcaceae, Oscillospiraceae, Acidaminococcaceae, and Lactobacillaceae in the Ab and Zn groups. Functional data analysis revealed a higher abundance of virulence genes in the Ct group microbiomes and heavy metal and antimicrobial resistance-related functions in the Zn treatment group. The results demonstrate that alternatives to Ab and ZnO should balance the microbial abundance and stimulate the growth of commensals to outcompete potential pathogens. IMPORTANCE Weaning is a critical period for piglets, during which potentially harmful bacteria such as Escherichia coli can increase in abundance in the intestine, creating digestive problems and diarrhea. In-feed antibiotics, the most frequent administration route for antibiotics in livestock, and therapeutic doses of zinc oxide (ZnO) help to control diarrhea but prompt secondary problems such as antimicrobial resistance and soil pollution from heavy metals. Understanding how these strategies impact the gut microbiota is crucial for establishing health biomarkers and designing successful replacement strategies. Using shotgun sequencing, this study compares the microbiota of pigs after early weaning when treated with in-feed antibiotics, ZnO, or treatment-free diets to describe differences that could define the susceptibility to infections, providing the basis for future research on improving intestinal resilience through microbiota-based strategies.

Effects of Different Nutritional Zinc Forms on the Proliferation of Beneficial Commensal Microorganisms

This study compared the minimal inhibition concentrations (MICs) and their effects on the growth kinetics of seven different types of zinc (Zn) compounds and Na2EDTA in the case of three typical commensal beneficial microorganisms (Bacillus subtilis, Lactococcus lactis, and Saccharomyces cerevisiae). The seven Zn compounds included ZnSO4, four Zn–amino acid chelates, and two Zn–EDTA complexes. Both MICs and growth kinetic parameters indicated that different microorganisms show different sensitivities; for example, B. subtilis, L. lactis, and S. cerevisiae were most sensitive to ZnSO4, Na2EDTA, and Zn(NH3)2(Gly)2, respectively. Both ZnEDTA and Zn(NH3)2(Lys)2 improved the growth rate of all beneficial commensal intestinal microorganisms at low concentrations (5–10 mg/L) and showed low toxicity towards all tested strains. At higher concentrations (100–500 mg/L), all compounds decreased the growth rate and increased the lag phase. In conclusion, both growth kinetic parameters and MICs tested effectively measured the inhibitory effects of the test materials; however, growth kinetics provides a more detailed picture of the concentration-dependent effects and those on the mechanisms of microbial growth inhibition.

Importance of Zinc Nanoparticles for the Intestinal Microbiome of Weaned Piglets

The scientific community is closely monitoring the replacement of antibiotics with doses of ZnO in weaned piglets. Since 2022, the use of zinc in medical doses has been banned in the European Union. Therefore, pig farmers are looking for other solutions. Some studies have suggested that zinc nanoparticles might replace ZnO for the prevention of diarrhea in weaning piglets. Like ZnO, zinc nanoparticles are effective against pathogenic microorganisms, e.g., Enterobacteriaceae family in vitro and in vivo. However, the effect on probiotic Lactobacillaceae appears to differ for ZnO and zinc nanoparticles. While ZnO increases their numbers, zinc nanoparticles act in the opposite way. These phenomena have been also confirmed by in vitro studies that reported a strong antimicrobial effect of zinc nanoparticles against Lactobacillales order. Contradictory evidence makes this topic still controversial, however. In addition, zinc nanoparticles vary in their morphology and properties based on the method of their synthesis. This makes it difficult to understand the effect of zinc nanoparticles on the intestinal microbiome. This review is aimed at clarifying many circumstances that may affect the action of nanoparticles on the weaning piglets' microbiome, including a comprehensive overview of the zinc nanoparticles in vitro effects on bacterial species occurring in the digestive tract of weaned piglets.

Dietary l-glutamic acid N,N-diacetic acid improves short-term maintenance of zinc homoeostasis in a model of subclinical zinc deficiency in weaned piglets

This study compared the Zn response in selected tissues of weaned piglets fed L-glutamic acid, N,N-diacetic acid (GLDA), while challenged with short-term subclinical Zn deficiency (SZD). During a total experimental period of eight days, 96 piglets were fed restrictively (450 g/d) a high phytate (9 g/kg) diet containing added Zn at 0, 5, 10, 15, 20, 25, 45 and 75 mg/kg with and without 200 mg/kg of GLDA. No animals showed signs of clinical Zn deficiency and no phenotypical differences were observed. Broken line analysis of Zn status parameters such as liver Zn and apparently absorbed Zn indicated that the gross Zn requirement threshold was around 55 mg/kg diet. Supplementation of Zn above this threshold led to a saturation of the response in apparently absorbed Zn and linear increase in liver Zn. Bone and serum Zn responded to the dose in a linear fashion, likely due to the time-frame of Zn homoeostatic adaptation. Inclusion of GLDA into the diets yielded a higher intercept for bone Zn (P < 0·05). Liver Zn accumulation and MT1A gene expression was higher for piglets receiving GLDA (P < 0·05), indicating higher Zn influx. This study indicates that a strong chelator such as GLDA mitigates negative effects of phytate in plant-based diets, by sustaining Zn solubility, thereby improving nutritional Zn availability.

Tannic acid extracted from gallnut prevents post-weaning diarrhea and improves intestinal health of weaned piglets

This experiment was conducted to evaluate the effects of different levels of tannic acid (TA) on growth performance, diarrhea rate, nutrient digestibility and intestinal health in weaned piglets. A total of 180 weaned piglets (Duroc × Landrace × Yorkshire, 24 d of age, initial average BW = 7.77 ± 0.17 kg) were allotted to 5 groups (6 pigs/pen and 6 replicates/group) in a randomized complete block design according to their gender and body weight. Piglets were fed a basal diet, or the basal diet supplemented with 0.05%, 0.1%, 0.2% or 0.4% TA for 28 d. The supplementary levels of TA in the diets were obtained by adding tannalbin containing 51% TA and 40.17% protein. The results showed that, compared with the CON group, dietary TA did not affect ADFI, ADG or F:G, and linearly reduced (P < 0.01) the diarrhea rate and diarrhea index of piglets. There were no significant effects on apparent total tract digestibility (ATTD) in the 0.05%, 0.1% and 0.2% TA groups, while negative effects (P < 0.05) on apparent digestibility of crude protein and gross energy were observed in the 0.4% TA group. In addition, the nutrient digestibility of dry matter, crude protein and gross energy linearly decreased (P < 0.01) with the increase of TA dosage. Supplementation of TA increased (P < 0.05) the villus height of the duodenum and jejunum, as well as increased (P < 0.05) catalase (CAT) activity in serum. Dietary TA improved (P < 0.05) the Bacillus counts in cecal digesta. Further, TA significantly improved (P < 0.05) Bacillus counts and reduced (P < 0.05) the Escherichia coli counts in colonic digesta. The concentration of acetic acid, propionic acid, butyric acid and isovaleric acid in cecal digesta were significantly increased (P < 0.05). The mRNA expression level of zonula occludens-1 (ZO-1), zonula occludens-2 (ZO-2), and claudin-2 (CLDN-2) in the jejunum were greater (P < 0.05) in TA supplemented groups. The study showed that, compared to the control, TA prevented post-weaning diarrhea and improved intestinal health of weaned piglets, and the appropriate level of TA supplementation would be from 0.1% to 0.2%.

The effects of pharmacological levels of zinc, diet acidification, and dietary crude protein on growth performance in nursery pigs

This experiment was conducted to evaluate potential replacements for pharmacological levels of Zn (provided by Zn oxide), such as diet acidification (sodium diformate) and low dietary crude protein (CP: 21 vs 18%) on nursery pig performance and fecal dry matter (DM). A total of 360 weaned pigs (Line 200 × 400, DNA, Columbus, NE; initially 5.90 ± 0.014 kg) were used in a 42-d growth study. Pigs were weaned at approximately 21 d of age and randomly assigned to pens (five pigs per pen). Pens were then allotted to one of eight dietary treatments with nine pens per treatment. Experimental diets were fed in two phases: phase 1 from weaning to day 7 and phase 2 from days 7 to 21, with all pigs fed the same common diet from days 21 to 42. The eight treatment diets were arranged as a 2 × 2 × 2 factorial with main effects of Zn (110 mg/kg from days 0 to 21 or 3,000 mg/kg from days 0 to 7, and 2,000 mg/kg from days 7 to 21), diet acidification, (without or with 1.2% sodium diformate), and dietary CP (21% or 18%, 1.40% and 1.35% in phases 1 and 2 vs. 1.20% standardized ileal digestible Lys, respectively). Fecal samples were collected weekly from the same three pigs per pen to determine DM content. No 2- or 3-way interactions (P > 0.05) were observed throughout the 42-d study for growth performance; however, there was a Zn × acidifier × CP interaction (P < 0.05) for fecal DM on day 7 and for the overall average of the six collection periods. Reducing CP without acidification or pharmacological levels of Zn increased fecal DM, but CP had little effect when ZnO was present in the diet. From days 0 to 21, significant (P < 0.05) main effects were observed where average daily gain (ADG) and gain:feed (G:F) increased for pigs fed pharmacological levels of Zn, sodium diformate, or 21% CP (P < 0.065). In the subsequent period (days 21 to 42) after the experimental diets were fed, there was no evidence of difference in growth performance among treatments. Overall (days 0 to 42), main effect tendencies were observed (P < 0.066) for pigs fed added Zn or sodium diformate from days 0 to 21, whereas pigs fed 21% CP had greater G:F than those fed 18% CP. Pig weight on day 42 was increased by adding Zn (P < 0.05) or acidifier (P < 0.06) but not CP. In summary, none of the feed additives had a major influence on fecal DM, but dietary addition of pharmacological levels of Zn or sodium diformate independently improved nursery pig performance.

Towards Zero Zinc Oxide: Feeding Strategies to Manage Post-Weaning Diarrhea in Piglets

Simple Summary

Zinc oxide (ZnO) supplementation at pharmacological doses in post-weaning piglets is a consolidated practice that allows efficient control of post-weaning diarrhea (PWD), a condition exacerbated by Escherichia coli F4 (K88) infections. Far from being completely elucidated, the multifactorial ZnO mechanism of action is in all likelihood exerted at the gastrointestinal level. However, increasing environmental concerns are arising from prolonged ZnO use. This article reviews the utilization of ZnO in piglets, the biological rationale behind its powerful activity, and the emerging threats that are leading towards a significant reduction in its use. Finally, a wide analysis of the strengths and weaknesses of innovative alternative strategies to manage PWD at the nutritional level is given.

Abstract

Zinc oxide (ZnO) at pharmacological doses is extensively employed in the pig industry as an effective tool to manage post-weaning diarrhea (PWD), a condition that causes huge economic losses because of its impact on the most pivotal phase of a piglet’s production cycle. In a multifactorial way, ZnO exerts a variety of positive effects along the entire gastrointestinal tract by targeting intestinal architecture, digestive secretions, antioxidant systems, and immune cells. ZnO also has a moderate antibacterial effect against Escherichia coli F4 (K88), the main causative agent of PWD. However, the environmental impact of ZnO and new emerging threats are posing serious questions to the sustainability of its extensive utilization. To work towards a future free from pharmacological ZnO, novel nutritional approaches are necessary, and many strategies have been investigated. This review article provides a comprehensive framework for ZnO utilization and its broad mode of action. Moreover, all the risks related to pharmacological ZnO levels are presented; we focus on European institutions’ decisions subsequently. The identification of a novel, complete solution against PWD should be accompanied by the adoption of holistic strategies, thereby combining good management practices to feeding approaches capable of mitigating Escherichia coli F4 (K88) infections and/or lowering ZnO utilization. Promising results can be obtained by adjusting diet composition or employing organic acids, natural identical compounds, polyphenol-rich extracts, prebiotics, and probiotics.

Dietary Preference of Newly Weaned Pigs and Nutrient Interactions According to Copper Levels and Sources with Different Solubility Characteristics

Two feeding preference experiments and an in vitro assay were performed to assess the weaned pig preference for Cu doses and sources based on their sensorial perception and on the likely post-ingestive effects of Cu. At day 7 post-weaning, a total of 828 pigs were distributed into two different experiments. In Exp.1 (dose preference) a diet with a nutritional Cu level (15 mg/kg) of Cu sulfate (SF) was pair offered with higher Cu levels (150 mg/kg) of either SF or hydroxychloride (HCl). In Exp.2 (source preference), a diet supplemented with Cu-SF at 150 mg/kg was compared to a Cu-HCl (150 mg/kg) diet. At the short-term (day 7-9) and for the entire experimental week (day 7-14), pigs preferred diets with a high Cu level than with Cu at a nutritional dose (p < 0.05). Likewise, pigs preferred diets supplemented with a Cu-HCl source compared to diets with Cu-SF (p < 0.05). In vitro assay results showed a greater solubility and interaction of Cu-SF with phytic acid compared to Cu-HCl. In conclusion, pigs chose diets with higher levels of Cu probably to re-establish homeostasis after weaning. Pigs preferred diets with Cu-HCl compared to Cu-SF probably due to their solubilities and chemical differences.

Zinc phosphate-based nanoparticles as alternatives to zinc oxide in diet of weaned piglets

BACKGROUND

The high doses of zinc oxide (ZnO) administered orally to piglets for the prevention of diarrhea and increase of growth rate can contaminate pig farms and the surrounding environment. Therefore, there is a need to find a replacement of high doses of dietary ZnO with an equally effective alternative. In the present study, the effect of two formulations of zinc phosphate-based nanoparticles (ZnA and ZnC NPs) on growth performance, intestinal microbiota, antioxidant status, and intestinal and liver morphology was evaluated. A total of 100 weaned piglets were randomly divided into 10 equal groups with the base diet (control) or the base diet supplemented with ZnA, ZnC, or ZnO at concentrations 500, 1000, and 2000 mg Zn per kilogram of diet. Supplements were given to animals for 10 days. Fecal samples were collected on day 0, 5, 10 and 20. At the end of the treatment (day 10), three piglets from each group were sacrificed and analyzed.

RESULTS

Comparing to that of control, the significantly higher piglet weight gain was observed in all piglet groups fed with ZnA (P < 0.05). Differences in the total aerobic bacteria and coliform counts in piglet feces after NPs supplementation compared to that of control and ZnO groups were also found (P < 0.05). The majority of aerobic culturable bacteria from the feces represented Escherichia (28.57-47.62%), Enterococcus (3.85-35.71%), and Streptococcus (3.70-42.31%) spp. A total of 542 Escherichia coli isolates were screened for the virulence genes STa, STb, Stx2, F4, and F18. The substantial occurrence of E. coli virulence factors was found on day 5, mainly in fimbrillary antigen and thermostable toxins, except for piglets fed by ZnC. Zn treatment decreased Zn blood levels in piglets fed with ZnO and ZnA (500 mg/kg) and increased in ZnC (2000 mg/kg) compared to that of control (P < 0.05). The antioxidant status of piglets was affected only by ZnA. While some changes in the liver and the intestinal morphology of piglets with NPs were observed, none were serious as reflected by the normal health status and increased weigh gain performance.

CONCLUSIONS

Our results indicate that ZnA NPs have a positive effect on the piglet growth performance even at the lowest concentration. The prevalence of E. coli virulence factors was lowest in pigs supplemented with ZnC. Zinc phosphate-based nanoparticles may be an effective alternative to ZnO.

Zinc overload in weaned pigs: tissue accumulation, pathology, and growth impacts

Zinc oxide (ZnO) is commonly fed to pigs at pharmacologic concentrations (2,000-3,000 ppm) for the first 3 wk post-weaning to increase growth and reduce enteric bacterial disease. The safety of this high-dose treatment is assumed based upon lower bioavailability of ZnO compared to other common forms of Zn in feed; however, limited data are available regarding the specific serum and tissue concentrations of Zn expected in animals experiencing overload following feeding of excessive ZnO. Fifty-five 3-wk-old pigs were divided into 5 groups receiving various concentrations of ZnO (0-6,000 ppm) for 3 wk. Pigs receiving 6,000 ppm ZnO had higher mean pancreatic Zn concentrations (p < 0.001) compared to other treatments, and higher pancreatic Zn concentrations were associated with pancreatic acinar cell apoptosis (p < 0.0001). Hepatic Zn concentrations were highest for pigs receiving 6,000 ppm ZnO (mean ± SEM; 729 ± 264 ppm) and significantly higher than all other groups (p < 0.0001), with controls having concentrations <60 ppm. Similarly, serum Zn was highest in pigs receiving 6,000 ppm ZnO (4.81 ± 2.31 ppm) and significantly higher than all groups (controls, <1 ppm). Additionally, as pigs became overloaded with Zn, there were significant reductions in serum Cu and both serum and hepatic Se. Hepatic and serum Zn concentrations >500 ppm and >2 ppm, respectively, are indicative of Zn overload, and dietary trace mineral analysis is warranted if expected inclusion rates are ≤3,000 ppm ZnO.

Impact of zinc and arginine on antioxidant status of weanling piglets raised under commercial conditions

The effects of dietary zinc and L-arginine supplements on the weight gain, feed efficiency, antioxidant capacity and oxidative status of weanling piglets raised under commercial conditions were examined. A total of 288 piglets aged 21 d were fed for 15 d a diet supplemented or not with 2,500 mg/kg of zinc (provided as zinc oxide) and 1% L-arginine·HCl. The 4 treatments were distributed in a randomized complete block design with 6 initial body weight categories (12 animals per pen). Access to feed and water was ad libitum. Data were analyzed as a 2 × 2 factorial experiment using the SAS MIXED procedure, with zinc and arginine as the main independent variables. Blood collection day (d 8 and 15, samples were collected from the same 2 piglets in each pen before the morning feeding) was included as a third factor. The zinc supplement increased the average daily gain (ADG) from d 0 to 7, d 8 to 15 and d 0 to 15 (0.289 vs. 0.217 kg/d), average daily feed intake (ADFI) from d 8 to 15 and d 0 to 15 (0.338 vs. 0.279 kg/d) and the gain to feed (G:F) ratio from d 0 to 7 and d 0 to 15 (0.86 vs. 0.77) (P < 0.001). Both supplements significantly decreased the malondialdehyde concentration (zinc: 4.37 vs. 3.91 μmol/L, P = 0.005; arginine: 4.38 vs. 3.89 μmol/L, P = 0.002). Total antioxidant capacity and reduced glutathione (GSH) increased from d 8 to 15 (0.953 vs. 1.391 μmol/L, 2.22 vs. 3.37 μmol/L, P < 0.05) regardless of dietary treatment. Total and oxidized GSH concentrations on d 8 were higher in response to the combined supplements (zinc × arginine interaction, P < 0.05). Piglets fed either Zn-supplemented diet had a lower haptoglobin serum concentration (509 vs. 1,417 mg/L; P < 0.001). In conclusion, the zinc supplement improved piglet growth performance (ADG and ADFI) and oxidative status (based on malondialdehyde concentration). The arginine supplement had a limited effect on growth performance and oxidative status under these conditions.

The effects of zinc amino acid complex supplementation on the porcine host response to Lawsonia intracellularis infection

Lawsonia intracellularis is among the most important enteric pathogens of swine and antibiotic alternatives are needed to help mitigate the negative effects of infection. Zinc is an essential trace mineral known to be crucial for maintaining intestinal barrier function and proper immune response. In this study, we investigated the porcine host response to L. intracellularis infection when supplemented with a zinc-amino acid complex, a form of zinc that can lead to greater bioavailability when compared to traditional inorganic forms of zinc. Our results show that a zinc-amino acid complex supplementation with a final concentration of 125 ppm of zinc in feed significantly (p < 0.05) decreased the number of animals with lesions and severity of lesions caused by L. intracellularis. Animals supplemented with the zinc-amino acid complex also exhibited a significantly (p < 0.05) earlier onset of seroconversion as well as an increased number of T cells in infected and non-infected intestinal tissue. This study demonstrated that this zinc-amino acid complex aids the host in responding to L. intracellularis infection and may be a new approach to help minimize negative effects of disease.

Zinc strengthens the jejunal barrier by reversibly tightening the paracellular route

During the postweaning period, piglets are prone to gastrointestinal infections. The resulting impairment of intestinal barrier function may cause diarrhea associated with growth retardation or even death of piglets. Orally applied Zn is commonly used to prevent and treat diarrhea, but its mode of action still needs to be elucidated. To analyze the molecular mechanism whereby Zn acts on porcine intestinal barrier function, ex vivo studies on piglet jejunum and accompanying in vitro studies on a porcine jejunal epithelial cell line, IPEC-J2/PS, were performed with electrophysiological tools. Feeding pharmacological Zn doses exerted no significant electrophysiologically ascertainable short- and long-term effects on jejunal barrier function ex vivo. However, in IPEC-J2/PS, basolateral Zn was cytotoxic since its application caused a release of lactate dehydrogenase and an irreversible breakdown of the epithelial barrier. In contrast, apical Zn application caused an immediate increase in paracellular resistance and a decrease in permeability to the paracellular marker fluorescein, reflecting overall barrier strengthening in vitro. Apical effects were fully reversible upon washout. This indicates that Zn supplemented to feed was completely washed out during ex vivo jejunum preparation. We conclude that there is no evidence for long-term barrier effects through prophylactic Zn supplementation and that extracellular Zn acts acutely and reversibly from the apical side via tightening the paracellular route, thus counteracting leak-flux diarrhea.NEW & NOTEWORTHY Therapeutically administered Zn successfully treats diarrhea in veterinary and human medicine. Here we present data that Zn strengthens the porcine jejunal epithelial barrier by reversibly tightening the paracellular route for inorganic ions and small solutes. Acute or long-lasting Zn effects on transcellular transport (Cl^- secretion) were not detected. We therefore conclude that Zn is useful for acutely treating leak-flux diarrhea rather than secretory diarrhea. Suitability as prophylactic feed supplement, however, is questionable.

Blood parameters as biomarkers in a Salmonella spp. disease model of weaning piglets

BACKGROUND

The weaning pig is used as an experimental model to assess the impact of diet on intestinal health. Blood parameters (BP) are considered a useful tool in humans, but there is very scarce information of such indicators in the weaning pig. The objective of the present study is to evaluate the use of different BP as indicators in an experimental model of salmonellosis.

METHODOLOGY

Seventy-two 28-day-old piglets were divided into four groups in a 2x2 factorial arrangement, with animals receiving or not a probiotic combination based on B. infantis IM1® and B. lactis BPL6 (109 colony forming units (cfu)/d) and orally challenged or not a week later with Salmonella Typhimurium (5x108 cfu). Blood samples of one animal per pen (N = 24) were taken four days post-inoculation for the evaluation of different BP using an I-stat® System and of plasmatic concentrations of zinc, iron and copper.

PRINCIPAL FINDINGS

Results reported marginal deficiencies of zinc in piglets at weaning. Moreover, plasmatic zinc, copper and iron presented good correlations with weight gain (r 0.57, r -0.67, r 0.54 respectively; P < 0.01). Blood electrolytes (Na+, Cl- and K+) decreased (P < 0.01) only when the performance of the animals was seriously compromised and clinical symptoms were more apparent. Acid-base balance parameters such as HCO3-, TCO2 and BEecf significantly correlated with weight gain, but only in the challenged animals (r -0.54, r -0.55, and r -0.51, respectively; P < 0.05), suggesting metabolic acidosis depending on Salmonella infection. Glucose was affected by the challenge (P = 0.040), while Htc and Hgb increased with the challenge and decreased with the probiotic (P < 0.05). Furthermore, correlations of Glu, Htc and Hgb with weight gain were observed (P < 0.05). Overall, BP could be regarded as simple, useful indexes to assess performance and health of weaning piglets.

Strategies and challenges to increase the precision in feeding zinc to monogastric livestock

Practical diets for monogastric livestock must be supplemented with zinc (Zn) due to their high contents of antagonistic substances like phytates. Current feeding recommendations include quite generous safety margins because of uncertainties regarding the gross Zn requirements under varying rearing conditions. Furthermore, the use of pharmacological Zn doses to stabilise animal performance and wellbeing is widespread. Taken together, modern diets for pigs and poultry contain considerably more Zn than necessary to meet animal requirements, which is associated with concerns related to the environment as well as animal and consumer safety. Therefore, European authorities most recently reduced the allowed upper limits for Zn in complete feed. To maintain animal productivity and wellbeing while reducing the Zn load in complete feed, all measures that stabilize feed Zn bioavailability must be applied. Most importantly, reliable information on the gross Zn requirement under practical conditions must be provided, considering the bioavailability of native or supplemented feed Zn, antagonisms with dietary factors as well as the physiological status of the animal.

Purified natural pig immunoglobulins can substitute dietary zinc in reducing piglet post weaning diarrhoea

Enteric infectious disease in weaner piglets, including postweaning diarrhoea (PWD), are usually treated and/or prevented with antibiotics and/or zinc oxide in the piglet feed. However extensive use of antibiotics and zinc oxide in intensive animal production is unwanted as it may promote microbial antibiotic resistance and pose environmental problems. Recently, in an experimental model of PWD, we observed that oral administration of purified porcine immunoglobulin G (ppIgG) from pooled natural pig plasma could reduce enteric infection. In the present study we were able to reproduce these results as it was observed that oral ppIgG accelerated clearance of faecal haemolytic bacteria in pigs challenged with E. coli in comparison with pigs not receiving ppIgG. This effect was observed upon feeding ppIgG for seven days postweaning suggesting that ppIgG does not have to be used prophylactically for several days preweaning. Furthermore, the effect of oral administration of ppIgG for seven days postweaning was equal to or better than that of dietary zinc oxide in reducing diarrhoea symptoms and in clearing faecal haemolytic bacteria for 14days postweaning. These observations warrant future trials of dietary ppIgG in intensive swine production units to establish its performance as an alternative to dietary antibiotics and zinc oxide for preventing PWD.

Accumulation of copper in the kidney of pigs fed high dietary zinc is due to metallothionein expression with minor effects on genes involved in copper metabolism

A study was conducted to determine the effect of high dietary zinc (Zn) oxide on trace element accumulation in various organs with special emphasis on the kidney. A total of 40 weaned piglets were allocated into two groups with 16 and 24 piglets each receiving a diet containing normal (NZn; 100mg Zn/kg) or high (HZn; 2,100mg Zn/kg) Zn concentration, respectively. After two weeks, eight piglets from each treatment were killed and organ samples were taken. Eight piglets from the remaining 16 pigs fed HZn diets were changed to NZn diets (CZn). All remaining piglets were killed after another two weeks for organ sampling. Trace element concentration was determined in the jejunum, liver, kidney, pancreas, bone (metacarpal IV), spleen, lung, thymus, tonsils and lymph nodes of jejunum, ileum and colon. Kidney mRNA expression of Zn transporter ZnT1 and ZIP4, genes involved in Cu metabolism (Ctr1, Atox1, SOD1, ATP7A, CCS, CP) and divalent metal ion transport (DMT1) and binding (MT-1a, MT-2b, MT-3) were determined. The Zn concentration in jejunum, liver, pancreas tissue and metacarpal IV was higher (P<0.05) in HZn group compared with NZn and CZn groups. Trace element concentration in organs of CZn pigs was similar to those fed NZn diets. Zn concentration in muscle, lung and lymphatic organs as thymus, tonsils, spleen and lymph nodes of jejunum, ileum and colon did not differ between the groups. Zn and Cu were positively correlated (R=0.67; P<0.05) in the kidney. No significant differences for Cu chaperones, Cu transporters and Cu-dependent factors were determined despite decreased expression of Atox1 after two weeks and increased Ctr1 expression over time in the HZn group. Expression of MT-1a, MT-2b and MT-3 were significantly higher in HZn fed pigs with most pronounced effects for MT-1a > MT-2b > MT-3. Gene expression of MTs in pigs fed CZn diets did not differ from pigs fed NZn diets. The data suggest that high dietary Zn feeding in pigs leads to Cu co-accumulation in the kidney of pigs with minor effect on genes relevant for Cu metabolism. In addition, the organ Zn and Cu accumulation is reversible after two weeks of withdrawal of high dietary Zn.

The Zinc Concentration in the Diet and the Length of the Feeding Period Affect the Methylation Status of the ZIP4 Zinc Transporter Gene in Piglets

High doses of zinc oxide are commonly used in weaned pig diets to improve performance and health. Recent reports show that this may also lead to an imbalanced zinc homeostasis in the animal. For a better understanding of the regulatory mechanisms of different zinc intakes, we performed a feeding experiment to assess potential epigenetic regulation of the ZIP4 gene expression via DNA methylation in the small intestine of piglets. Fifty-four piglets were fed diets with 57 (LZn), 164 (NZn) or 2,425 (HZn) mg Zn/kg feed for one or four weeks. The ZIP4 expression data provided significant evidence for counter-regulation of zinc absorption with higher dietary zinc concentrations. The CpG +735 in the second exon had a 56% higher methylation in the HZn group compared to the others after one week of feeding (8.0·10-4 < p < 0.035); the methylation of this CpG was strongly negatively associated with the expression of the long ZIP4 transcripts (p < 0.007). In the LZn and NZn diets, the expression of the long ZIP4 transcripts were lower after four vs. one week of feeding (2.9·10-4 < p < 0.017). The strongest switch leading to high DNA methylation in nearly all analysed regions was dependent on feeding duration or age in all diet groups (3.7·10-10 < p < 0.099). The data suggest that DNA methylation serves as a fine-tuning mechanism of ZIP4 gene regulation to maintain zinc homeostasis. Methylation of the ZIP4 gene may play a minor role in the response to very high dietary zinc concentration, but may affect binding of alternate zinc-responsive transcription factors.

Impact of high dietary zinc on zinc accumulation, enzyme activity and proteomic profiles in the pancreas of piglets

The exocrine pancreas plays an important role in zinc homeostasis. Feeding very high (2000-3000mgzinc/kg diet) levels of zinc oxide to piglets for short periods is a common practice in the swine industry to improve performance and prevent diseases. The impact on pancreatic function and possible side effects during long-term feeding of high dietary zinc levels are still poorly understood. A total of 54 weaned piglets were either fed with low (57mg/kg, LZn), normal (164mg/kg, NZn) or high (2425mg/kg, HZn) zinc concentration in the diets. After 4 weeks of feeding, ten piglets per treatment were euthanized and pancreas samples were taken. Tissue zinc concentration and metallothionein abundance was greater with HZn compared with NZn and LZn (P<0.05). Similarly, activity of α-amylase, lipase, trypsin and chymotrypsin was higher with HZn as compared with NZn and LZn diets (P<0.05), whereas elastase activity was unchanged. Total trolox equivalent antioxidative capacity of pancreas tissue was higher with HZn diets compared with the other treatments (P<0.05). Pancreatic protein profiles of NZn and HZn fed piglets were obtained by 2D-DIGE technique and revealed 15 differentially expressed proteins out of 2100 detected spots (P<0.05). The differentially expressed proteins aldose reductase, eukaryotic elongation factor II and peroxiredoxin III were confirmed by immunoblotting. Identified proteins include zinc finger-containing transcription factors and proteins mainly associated with oxidative stress response and signal transduction in HZn compared with NZn pigs. Histologic examination however showed no morphologic changes. The results suggest that long-term supply of very high dietary zinc increases zinc and metallothionein concentration, and digestive enzyme activity, but also triggers oxidative stress reactions in the pancreas of young pigs. The data provide new insights into pancreatic function under outbalanced zinc homeostasis.

Effects of a lipid-encapsulated zinc oxide supplement on growth performance and intestinal morphology and digestive enzyme activities in weanling pigs

This study compared the effects of varying lipid content and dietary concentration of a lipid-encapsulated (LE) ZnO product to those of native ZnO and thereby to find insights into optimal lipid coating and dosage of the Zn supplement. A total of 192 21-d-old weanling pigs were allotted to 48 pens, after which each six pens received a ZnO-free basal diet supplemented with 125 ppm ZnO (100 ppm Zn; BASAL), 2,500 ppm Zn as native ZnO (HIGH), or 100 or 200 ppm Zn as LE ZnO (LE-100 or LE-250) containing 8%, 10%, or 12% lipid [LE-8%, LE-10%, or LE-12%, respectively; 2 × 3 factorial arrangement within the LE-ZnO diets (LE-ALL)] for 14 d. Forty pigs were killed at the end for histological and biochemical examinations. None of ADG, ADFI, gain:feed, and fecal consistency score differed between the LE-ALL and either of the BASAL and HIGH groups. Hepatic and serum Zn concentrations were greater (p <0.05) in the HIGH vs. LE-ALL group, but did not differ between LE-ALL and BASAL, between LE-100 and -250, or among LE-8%, -10%, and -12% groups. Villus height (VH), crypt depth (CD), and the VH:CD ratio in the duodenum, jejunum, and ileum did not differ between the LE-ALL and either of the BASAL and HIGH groups, except for a greater CD in the duodenum in the LE-ALL vs. HIGH group. Additionally, VH and CD in the duodenum and VH:CD in the jejunum were greater in the LE-250 vs. LE-100 group. Specific activities of sucrase, maltase, and leucine aminopeptidase in these intestinal regions and those of amylase and trypsin in the pancreas were not influenced by the lipid content or dietary concentration of LE ZnO and also did not differ between the LE-ALL and either of the BASAL and HIGH groups, except for a greater pancreatic amylase activity in the former vs. HIGH group. In conclusion, the present results indicate that the LE ZnO, regardless of its lipid percentage or supplementation level examined in this study, has no significant effect on growth performance, fecal consistency, or digestive enzyme activities of weanling pigs under the experimental conditions.