Effects Of Alternative ZnO On Growth Performance Intestinal Function And Its Mechanism In Weaning Piglets

Weaning is the most important phase to piglets. Environmental, nutritional and psychological stressors accompanied by microbiological, immunological and physiological changes in immature gastro-intestine could cause diarrhea and growth reduction. Until strictly limited by European Union (EU) in 2006, antibiotics were replaced many nutritional strategies, such as zinc oxide (ZnO), probiotics, prebiotics, organic acids and essential oils, to control diarrhea and promote growth in weaning piglets. Pharmacological dosages (2000-4000 mg/kg) of ZnO have been used as effective diarrhea prophylaxis and growth promoter in weaning piglets for over 20 years. However, concerning consequent toxicity, resistance and pollution of high-level zinc supplementation, EU implemented an upper limit of 150 mg/kg. It is imperative to find alternatives to pharmacological dosages of ZnO to avoid similar mistakes of antibiotics abuse and keep long-term interests of swine industry. Other nutritional strategies mentioned above and different zinc sources could not replace ZnO effectually due to different action modes. Other forms of ZnO, such as nano ZnO, porous ZnO and ZnO-Silicate composites were considerable, while there are still some concerns about instable effects and safety risks. In this study, a design strategy of alternative ZnO (AZO) to ordinary zinc oxide, large specific surface area and micro-scale particle size, was testified by evaluating effects of its product on growth performance, diarrhea and intestinal function of weaning piglets.1 Preparation and characterization of AZOAZO was prepared according to TGA results of BZC. And different forms of ZnO was characterized and compared by SEM, TEM, BET, UV-Vis and Zeta-potential, which showed that abundant pores and inner beams formed the largest surface area (48.9 m2/g) and micro-scale (10-30 μm) particles. The structure of AZO could prevent resolving from simulated gastric fluid. AZO has better antibacteria activity on E. coli K88, S. aureus and S. enteritidis, and could shorten E. coli K88 and form a film on the surface of bacteria. Furthermore, AZO has better proliferation and lower cytotoxicity, and no influence on intracellular ROS level.2 Effects of AZO on growth performance and diarrhea in weaning pigletsThree animal experiments were conducted to evaluate the effects of AZO on ADG, ADFI, G:F and diarrhea ratio in weaning piglets. Exp.1,56 weaning piglets (Duroc x Landrace x Hei, weaned at 25 ± 1 d, mean BW of 7.33 ±0.18 kg) were randomly allotted to 4 groups:basal diet+3000 mg/kg of OZO; basal diet+300 mg/kg of NZO; basal diet+300 mg/kg of PZO; basal diet+300 mg/kg of AZO. Exp. 2,165 weaning piglets (Duroc x Landrace, weaned at 21 ± 1 d, mean BW of 6.40 ± 0.59 kg) were randomly allotted to 5 groups:basal diet+3000 mg/kg of OZO; basal diet+300 mg/kg of OZO; basal diet+600 mg/kg of AZO; basal diet+300 mg/kg of AZO; basal diet+150 mg/kg of AZO. Exp.3,90 weaning piglets (Duroc x Landrace x Yorkshire, weaned at 25 ± 1 d, mean BW of 7.88 ± 1.00 kg) were randomly allotted to 3 groups:basal diet+3000 mg/kg of OZO; basal diet+300 mg/kg of AZO; basal diet+300 mg/kg of AZO, probiotics substituted for antibiotics. Results showed that 300 mg/kg of different ZnO forms (nano ZnO, porous ZnO and AZO), different dosages (600 and 300 mg/kg) of AZO and different combinations (with antibiotics or probiotics) of AZO were all as efficacious in promoting growth and reducing diarrhea as controls (3000 mg/kg of OZO).3 Effects of AZO on digestion and Zinc metabiolism in weaning pigletsCompared with 3000 mg/kg of OZO,300 mg/kg of AZO could improve apparent digestibility and digestive enzymes activities in duodenal contents. It could reduce fecal and liver zinc (P<0.01), but not influence serum zinc levels (P>0.05). It could improve ZIP4 mRNA expression levels (P<0.05), while not influence SLC30 family (ZnTl, ZnT2 and ZnT5). It could also reduce MT1 mRNA expression levels (P<0.05) and improve T-AOC (P<0.01) via increasing enzyme activities of SOD and CAT in serum.4 Effects of AZO on intestinal barrier function in weaning pigletsCompared with 3000 mg/kg of OZO,300 mg/kg of AZO could maintain intestinal structure, improve mRNA expression level of tight junction protein (claudin-1, occludin, ZO-1 and ZO-2), mucins (MUC1, MUC2, MUC4, MUC13 and MUC20) and anti-microbial peptides (pBD-1 and pBD-2). It could also enhance secretion of ileal sIgA and improve microbiota abundance and diversity in ileum.In summary, based on the strategy "large specific surface area and micro-scale particle size", AZO was prepared which had better antibacteria activity and lower cytotoxicity. Compared with 3000 mg/kg of OZO,300 mg/kg of AZO was efficacious in preventing diarrhea, promoting growth, improving digestion and enhancing intestinal barrier function.