Effects Of Pharmacological Levels Of Dietary Copper And Zinc On Small Intes-Tinal Morphology, Histochemical Pre-Cipitation And Intestinal Microbiota In Weaned Piglets

A2×2factorial trial (twelve28±d of age weaned piglets per treatment divided into four replicates) was conducted to investigate the effects of dietary supplementation with two levels of copper (20or250mg kg-1Cu as feed grade CuSO4·H2O) and/or zinc (80or2500mg kg-1Zn as feed grade ZnO) on growth performance, nutrient utilization, small intestinal morphology, tissue Cu and Zn levels, tissue Cu and Zn precipitation profiles as well as intestinal microbiota in weaned piglets for the duration of21d. Antibacterial agents were not included in the basal diet. The diets were fed in meal form, and the pigs were allowed to ad libitum access to their diets and water.Trail1Effects of pharmacological levels of dietary copper and zinc on growth perfor-mance, nutrient utilization and small intestinal morphology in weaned pigletsForty eight (eight litters of six)28-d weaned crossbred (Landrace×Yorkshire) piglets with an average initial body weight (BW) of (6.21±0.43) kg were randomly assigned to four dietary treatments based on litter origin, BW and gender with four replicates per treatment and three piglets per pen. BW of individual piglet and feed intake of respective pen were recorded on a weekly basis, according to which the average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR) of the entire3-week trial period were calculated. In the last week of the total trail period, chromic oxide was added to all four rations at0.3%(W/W) as an external inert indicator, and the fecal samples were collected in that week when pigs had a4-d adjustment period fol-lowed by a3-d total collection period. The fecal samples were used for the calculation of apparent nutrient digestibilities.3-cm sections representative of the duodenum, jejunum and ileum removed from each of the slaughtered piglets in four dietary treatments were collected for further morphologic analysis on the last day of the experiment. Results showed that high dietary Cu can significantly increase the FCR (P=0.013), whereas high dietary Zn can improve the feed intake of the piglets (P=0.022). However, there was no Cu and Zn interaction observed on the growth rate of piglets. In addition, high dietary Cu can improve the apparent digestibities of dry matter (P=0.018), crude protein (P=0.001), ether extract (P=0.006) and digestive energy (P=0.007), but high dietary Zn had little in-fluence on these parameters except inhibiting the apparent digestibilities of dry matter (P=0.001) and digestive energy (P=0.004). The small intestinal villus height and villus height to crypt depth ratio of piglets can be improved by ethier high dietary Cu or dietary Zn.Trail2Effects of pharmacological levels of dietary copper and zinc on tissue Cu and Zn contents and precipitation profiles in weaned pigletsAtomic absorption spectrophotometry (AAS) and tissue copper and zinc ions in situ de-velopment methods (i.e., rubeanic acid staining and immersion autometallography, iZn-SAMG) were employed to evaluate the absolute concentrations and precipitation laws of Cu and Zn in duodenum, jejunum, ileum, liver and kidney of piglets. The concentrations of Cu and Zn in the serum of piglets were also determined by AAS. Results revealed that high dietary Cu can increase the copper levels in duodenum (P<0.001), jejunum (P<0.001), ileum (P<0.001), liver (P<0.001) and kidney (P<0.001); zinc levels in duo-denum (P=0.001) and jejunum (P<0.001), and only decrease the zinc level in liver (P<0.001) of piglets. High dietary Zn showed a similar pattern on tissue zinc levels of piglets as high dietary Cu on tissue copper contents. However, it decreased the copper levels in all tissues mentioned above (P<0.001) except in duodenum. Further more, high dietary Cu elevated the serum copper concentrations (P=0.010) and high dietary Zn re-duced the serum zinc concentrations (P=0.009) of piglets. Hence, it can be concluded that high dietary zinc can have a negative effect on adequate dietary copper, but high dietary zinc may have little effect on adequate dietary zinc. Additionally, it is an inspiring finding that both rubeanic acid staining and iZnSAMG methods can successfully detect the copper or zinc ions in different tissues where high concentrations of Cu or Zn were accumulated. As a result, the two staining protocols can be further applied in the investigation of cell Cu and Zn metabolic pathway on ultrastructural levels after weaned piglets ingested high concentrations of dietary Cu and/or Zn.Trail3Effects of pharmacological levels of dietary copper and zinc on intestinal mi-crobiota in weaned piglets16S rRNA gene based denaturing gradient gel electrophoresis (DGGE) and real-time PCR techniques were employed to analyze the changes in pig intestinal bacterial com-munity compositon and population sizes of total bacteria, E. coli and lactobacill with the inclusion of high dietary Cu and/or Zn. Results revealed that high dietary Cu can sup-press the population of lactobacilli in pig jejunal digesta, but had little influence on the population of E. coli; high dietary Zn can improve the diversity of pig small intestinal bacterial community compostion as well as the gram-negative bacterial population. Hence, a proposed mechanism was established. It is likely that improved diversity and stability of bacterial community in the proximal part of the intestinal tract may contribute to the growth-promoting effects of high dietary Cu and Zn on weaned piglets.