Zinc oxide in weaned pig diets
The intestinal microbes change when the piglets are weaned, and the piglet’s immune system is not mature at this time. At this time, some pathogenic bacteria, such as enterotoxin-producing Escherichia coli, will invade, colonize and multiply, which is also the cause of our common post-weaning diarrhea, accompanied by growth restriction. Zinc oxide is a very good choice among all available feed additives. It is very clear that zinc oxide has an antibacterial effect. Recently, a combination of gene sequencing and PCR amplification has proposed a new perspective on the intestinal microbial effects of zinc oxide (3kg/T) on weaned piglets. In vitro tests showed that from the minimum inhibitory concentration of zinc oxide on 75 strains in pig intestines, it is difficult to find out the difference in sensitivity of different strains to different concentrations of zinc oxide from the origin of strain classification. However, compared with Enterobacter and lactic acid bacteria, strict anaerobic bacteria showed a diversity of the minimum inhibitory concentration of zinc oxide. Compared with the simple classification of bacteria into Galanz-positive bacteria and Galanz-negative bacteria, the role of zinc oxide is more specific to the species. High-dose zinc oxide was found to inhibit the growth of microorganisms in the stomach and jejunum of weaned piglets under simulated conditions. Compared with other microorganisms, lactic acid bacteria were more susceptible to high doses of zinc oxide. When piglets fed a diet containing 3000 mg/kg zinc oxide, the diversity of the intestinal flora of the piglets increased, but the number of Enterobacteriaceae, Escherichia and lactic acid bacteria decreased.
Even though we already understand the role of zinc oxide in the intestinal microbes of weaned piglets, we still have a lot of questions:
– How does zinc oxide affect the metabolism and health of microorganisms?
– Is the positive effect of zinc oxide on the intestinal health of piglets limited to its bacteriostatic activity?
– Does zinc oxide from different sources have the same effect?
Mechanism of action of zinc oxide
Zinc oxide is a water-insoluble compound, but zinc oxide undergoes dissociation at low pH. The acidic environment in the stomach of piglets is very weak. Coupled with the immature digestive system of the piglets and the buffer system formed by the stomach sputum, the dissociation of zinc oxide in the stomach of piglets is very limited. Once zinc oxide is dissociated, the dissociated Zn2+ enters the gastrointestinal tract. It is generally believed that the antibacterial activity of zinc oxide comes from these dissociated zinc ions, and the dissociated zinc ions interact with the amino acid groups of the microorganisms and then inhibit active transport. If the bacteriostatic activity of zinc oxide depends on the dissociated finite zinc ions, the higher water solubility of zinc sulphate will exert a better antibacterial effect by dissociating more zinc ions. but it is not the truth. Recent studies have confirmed that the action of zinc oxide comes from zinc oxide molecules. The contribution of zinc ions dissociated from zinc oxide to the bacteriostatic action of zinc oxide is also different depending on the type of microorganism, but the contribution value is very low. For E. coli, the disintegrated zinc ion contributes only 15% of the bacteriostatic action.
If the positive effect of zinc oxide on the intestinal health of piglets is only derived from the bacteriostatic action of zinc oxide is still controversial. In many hypotheses about the mechanism of action of zinc oxide, in a dark environment, zinc can produce reactive oxygen free radicals under ultraviolet light, which can cause serious damage to cells. Reactive oxygen free radicals include oxidative stress, and reactive oxygen free radicals can cause oxidation of microbial lipid membranes, which in turn can cause changes in cell membrane composition. This can also explain to some extent that zinc oxide can reduce the pathogen (such as E. coli) to the host. Adherence of cells. The reduction of adhesion of pathogenic bacteria to epithelial cells can effectively reduce the secretion of enterotoxin. At present, the antibacterial mechanism of zinc oxide is not very clear, and it will be different due to the different mechanisms of action of cells, but it is recognized that zinc oxide must play a certain mechanism. The role of zinc oxide in improving intestinal health depends on the chemical properties of the zinc oxide product particles.
Not all zinc oxide is the same
The sources of zinc oxide vary widely. Standardized analytical grade trace elements cannot be used to extrapolate feed grade trace elements.
Nano-zinc oxide will be different from conventional zinc oxide. The feed industry will have some interest in nano-zinc oxide, but before using nano-zinc oxide, you need to recognize the following points: use the correct analytical method to identify; Whether the samples are representative; ADME (absorption, dispersion, metabolism, excretion) and toxicity studies on animals; impact on the personal safety and environmental safety of operators; and understanding whether local regulations permit use.
Active zinc oxide
The active zinc oxide produced by the patented process, zinc sink, has been used in the animal feed industry. The patented process has modified the physicochemical properties of zinc oxide, and the particle size, particle shape and specific surface area have been changed. The specific surface area of microporous zinc is 10-15 times higher than that of conventional zinc oxide. Micropores greatly increase the specific surface area of zinc oxide, and the increase in surface area greatly increases the chance of contact between zinc oxide and intestinal microorganisms, thereby increasing the antibacterial activity of microporous zinc oxide. Scientific research has also confirmed that microporous zinc oxide can more effectively control the growth of microorganisms in the intestines and chyme.
In vitro antibacterial
In vitro experiments at the University of Berlin in Germany compared the inhibitory effects of conventional zinc oxide and zinc on the growth of the pathogen, Escherichia coli (E. coli PS79/K88/F4 and PS7/K81/F18). Under the conditions of simulating the stomach of the weaned piglets (pH 4.6) and the intestinal tract (pH 6.5), the zinc sulphate always showed a higher inhibition of E. coli growth than the conventional zinc oxide.
Inhibiting the bacteriostatic action in the in vivo environment
Optimizing gut microbes not only reduces harmful bacteria, but also reduces the attachment of other microbes to the gut. Vahjen et al. (2012) compared the inhibitory effects of conventional zinc oxide and zinc on the microbes in the stomach and jejunum of weaned pigs. Compared with conventional zinc oxide, the inhibition of microbial growth by zinc (HiZox®) showed significant differences.
Inhibition of small intestinal microflora
The research team at Ghent University in Belgium (Michiels, 2016) feeds weaned piglets with 110 mg/kg Zn (from zinc oxide, negative control); 3 kg/T zinc oxide (positive control); 110 mg/kg Zn The number of E. coli and E. coli groups in the small intestine was determined after four diets (and 220 mg/kg Zn). The test results show that low doses of zinc can effectively reduce the number of E. coli and E. coli groups in the small intestine.
Escherichia coli pathogenic factor in feces
In the trials conducted by the University of Berlin in Germany (Vahjen, JAS in press), weaned piglets were fed four (negative control, diet containing 110 mg/kg Zn, Zn from zinc oxide; positive control, diet containing 3 kg /T ZnO; zinc group 1, the diet contains 110 mg / kg Zn, Zn from sink zinc; sink zinc group 2, the diet contains 220 mg / kg Zn, Zn from sink zinc) test diet, and then by PCR Determine the total number of Enterobacter, Escherichia coli, and E. coli virulence factors in the feces of weaned piglets. More than half of the samples in the negative control group were positive for E. coli, and the proportion of E. coli cytokine positive in the other three treatment groups was much lower.
Fecal microbial flora
In a trial conducted by Dankook University (Choetal, Anim. Sci. Journ. 2015), weaned pigs were fed different doses of zinc oxide from different sources (negative control, Zn only from 110 mg contained in the premix) /kg Zn; positive control, containing 3 kg / T ZnO; zinc group, 300 mg / kg and 200 mg / kg zinc in the pre-conservation and post-conservation materials, respectively, and then measured different doses and oxidation of different sources The effect of zinc on growth performance, nutrient digestibility, blood biochemical parameters, fecal microbes, and fecal molding scores in weaned piglets. The test results show that zinc (HiZox®) changes the proportion of lactic acid bacteria/E. coli in the feces, thereby increasing the molding fraction and growth performance of the feces.