Studies On Nutritional And Physiological Effects Of Nanometer Zinc Oxide

In this paper, six experiments were conducted to investigate the nutritional and physiological effects of nano - ZnO. The bulk weight of different size nano-ZnO, feed grade ZnO and ZnSO₄ were measured , and the free Zn²⁺ concentrations from different zinc sources in simulative condition of piglets gastric or intestinal tract were determined in the experiment 1. Then, in experiment2, eighteen piglets (Landrace XTai) weaned at d 28 fed diets with 100mg/kg Zn from different zinc sources containing 100nm Nano-ZnO, feed grade ZnO and ZnSOi were divided into three treatments randomly during the 21-day growth assay. It was conducted to determinate the effects of different zinc sources on growth performance and biological indexes containing zinc, alkaline phosphatase(AKP),calcium, phosphorus, glucose, amylase, total protein , albumin and immunoglobulin(IG) and glutamic-pyruvic transaminase(GPT) in serum. In experiment 3, eighteen piglets (Landrace×Tai, initially weaned at d 28) were divided into three treatments at random. During the 28 d , growth regulation of piglets was conducted with diets containing Nano-ZnO(30-50nm)in high zinc level. Furthermore, 80 Duroc X Landrace X Yorkshire crossbred weanling pigs (weaned at d 21 and initial weight 8.1kg) were selected, and were blocked by initial weight and randomly allotted to one of ten dietary treatments with nano-ZnO(20nm) in experiment 4. studies on growth performance and diarrhea ratio of piglets and the community of fecal microorganism in 42-d growth assay. And the changes of serum zinc, AKP, growth hormone (GH) and immunoglobulin (IG) in different treatments in same stage and in different stage in same treatment were determined. In experiment 5, the study on absorption rate of zinc from different zinc sources(nano-ZnO(20nm), feed grade zinc oxide and zinc sulfate) by everted gut sacs trial of piglets was conducted. Pigs were slaughtered In experiment 6, thirty piglets (Landrace×Landrace×Tai, weaned at d28) were fed diets with 20nm nano-ZnO, feed gradeZnO or ZnSOl in five treatments, measured the amount of zinc in liver, kidney, duodenum, spleen, heart and longissimus dorsi (LD), and MT in liver and kidney . RNA/DNA in LD, duodenum and liver.The results showed as follows:(1) The performance of piglets fed diets containing 20 nm nano-ZnO is better than that containing feed grade ZnO or ZnSO4. At the first stages (l²weeks) , the average daily gain (ADG) and average daily feed intake(ADFI) of piglets fed diet with 2500 mg/kg zinc from nano-ZnO (20 nm) were improved significantly(p<0. 05). There is a linear relation between ADG and the dosage of nano-ZnO in l-2weeks (p<0. 05) . The growth performance of piglets containing 50 mg/kg zinc from nano-Zn0(20 nm) was better than that of other treatments in 3-6 weeks and in the whole trial. The E. coli. amount in feces of piglets fed diets with Nano-ZnO was reduced markedly(p<0. 05), and diarrhea rate of piglets decreased markedly(p<0. 01), respectively; the amount of nano-ZnO given were more and the E. coli. amount in feces(p<0. 05) and diarrhea rate were less(p<0. 01). The concentrations of serum zinc and AKP of piglets fed diets with Nano-ZnO were improved significantly (p<0. 05), and the decrease of the growth hormone(GH) level in serum were stayed, then immune globulin level were not impacted markedly (p>0.05). And the use of nano-ZnO can significantly economize zinc source that was so limited.(2) The absorption rate of zinc from 20 nm nano-ZnO is higher than that of feed grade ZnO and ZnS0i(p<0. 05), and absorbed mainly in fast stage. The absorptive speed decreased with the time in quadratic curve(p<0.05). The regression equation as follows: y=0. 8502-0. 9617x +0. 2852x2 (R2=0. 99, P=0. 001, y : absorptive speed of ZnSO1. %/min; x: min ); y=l. 5398-1. 5234x+0.4102x2 ( R2=0. 930 , P=0. 019, y : absorptive speed of 20nm ZnO, %/min; x: min) ; y=0.6338-0.6384x +0. 1723x2 (R2=0.940, P=0.015, y : absorptive speed of feed grade ZnO. %/min; x: min).(3) The amount of zinc in tissue and organs significantly increased in 20 nm nano-ZnO treatments, the deposit amount of zinc in tissue and organs markedly increased with dosage enhancement of 20 nm nano- ZnO(p<0. 01). The deposit positions of zinc from nano-ZnO were liver, kidney and duodenum. The ratio of RNA/DNA and the amount of MT in tissues and organs of piglets in nano-ZnO treatments increased (p<0. 01). The effects of nano-ZnO on physiological effects of piglets were larger than that on production performance.(4) The growth performance of piglets in 30-50nm nano-ZnO treatment with 2000mg/kg zinc from nano-ZnO was higher than that in feed grade ZnO treatment with 3000mg/kg zinc (p <0. 05), ADG and feed conversion rate (FCR ) of piglets in 30-50nm ZnO treatment with lOOmg/kg zinc were better than that in feed grade ZnO treatment with 3000mg/kg zinc(p>0. 05). But the growth performance of piglets in lOOnm ZnO or feed grade ZnO treatment with 100 mg/kg zinc was lower than that in ZnSO4 treatment with lOOmg/kg zinc. By contrast to feed grade ZnO, lOOnm Nano-ZnO added clearly improved ADFI and concentration of serum zinc and AKP of piglets, and did not impact the concentrations of calcium, phosphorus, activity of transaminases and levels of immunoglobulin(IG ) in serum(p>0. 05).(5) Nano-zinc oxide in different size range has different bulk weight, and bulk weight of nano-ZnO is significantly less than feed grade ZnO and ZnS04(p<0. 01), bulk weight of 20nm nano-ZnO less than 30-50 nm nano-ZnO and lOOnm nano-ZnO(p<0.01).The percent of free ZnJ from 20 nm nano-ZnO muddle solution was 1.42% or 0.22%, respectively, in pH 4.0 or 7.5 condition. It was 1.82% or 0.3% of free Zn2' from ZnSOi solution in same pH condition. The 98 percent of nano-ZnO existence in simulative condition of weanling piglet gut tract was non-ion form.In conclusion, the smaller size of nano-ZnO, the better response of growth improvement. The growth performance of piglets fed diets containing nano-ZnO in the size range less than 50nm were improved remarkably. And the growth performance of piglets fed diets containing low dosage nano-ZnO were markedly improved in 3-6 weeks and in the whole trial. After that, the limited zinc sources were economized. Nano-ZnO had higher bioavailability .biological activity and biocompatibility than feed grade ZnO and ZnSOi. Nutritional and physiological effects of nano-ZnO were based on high absorption rate. The effects of nano-ZnO on piglets nutritional and physiological responses were more significant than growth performance of piglets.