**14. Special aspects of nanominerals**

Trace minerals such as Se is essential in minute quantities in poultry diet to reduce stress, improve immunity and overall health, but safe limit of inorganic Se is very narrow. Hu et al. [51] observed a wider range between the optimal and toxic dietary levels of nano-Se compared to inorganic sodium selenite in broiler chickens. But contradictory reports exist regarding occurrence of severe pathological changes in liver due to increase in nano-Se concentration from 0.15 to 0.3 mg/ kg diet [124]. One of the possible mechanisms of nano-Se action in poultry could be conversion of nano-Se into selenite, H2Se or Se-phosphate followed by synthesis of selenoproteins by gut microbiota, which was also reported by Surai et al. [125] in *Veiollonella*. Reports suggest lower toxicity of Se NP than selenomethionine [126]. Also, Gangadoo et al. [127] reported that nano Se did not cause any damage to epithelial cells in the digestive system and neuronal bodies in brain tissue signifying its lesser toxicity in animal models. Nano-Ag in higher concentration (8 and 12 mg/ kg diet) had detrimental effect on organs such as liver [128]. Ag-NP supplementation in drinking water (15 mg/L) of broilers had no significant growth promoting or coccidiostat action [129]. At higher concentration (50 mg/L) in drinking water, no effect on the intestinal colonization of C. jejuni was found; however, reduced body weight gain was observed in broiler chickens [130]. Dietary ZnO NP at 40 and 60 mg/kg alleviated the negative results of heat stress evident from lowering of serum corticosterone level [131]. Saki and Abbasinezhad [132] reported improved embryonic growth and development in broiler on supplementation of 25 mg/kg diet of nano-Fe and 100 mg/kg diet of Fe-nano-alimet chelate. But toxicity of nano-FeO was reported in chick embryo possibly due to its interaction with egg albumen.

*Advances in Poultry Nutrition Research*

were expressed quickly by Cu-NP [107].

delivery and diagnostics [110].

**12. Nanominerals as antimicrobial feed additives**

coarse CuSO4 [106]. A study involving Cu-NP, agglomerates of Cu-NP and Cu microparticles on the metabolism in broiler chickens after a single intramuscular injection revealed that all these forms had growth stimulating effect along with increased red cell level, hemoglobin, Cu and protein in blood serum, where effects

Pathogenic microbial load in the gut of poultry is detrimental as they reduce growth rate, feed efficiency and mortality, and are some of these contaminants may survive during food processing and storage. The in-feed antibiotics used for preventing the pathogens as well as growth promoters has been great concern due to possible emergence of drug resistance in microbes as well as appearance of the drug residue in poultry products and subsequently affecting consumer's health [108]. There is an optimism of using nano-minerals as antibiotic alternatives due to their antimicrobial properties [109]. NP use has been established in therapeutics, drug

Many research carried has explored the antimicrobial action of metal oxide-NP [109]. Nano-Ag supplementation at 4 mg/kg diet in broiler chickens reduced serum cholesterol, aspartate aminotransferase levels and reduced caecal *Escherichia coli*, but had no significant effect on Lactobacillus count [70]. Nano-Ag in water (25 mg/ kg) increased the population of lactic acid bacteria without any adverse effect on enterocytes of duodenal villi [111]. Nano-Ag lowered the number of *Escherichia coli*, *Streptococcus*, *Salmonella*, and total mesophilic bacteria in the litter [112]. ZnO-NP was found be effective against both gram positive and gram-negative bacteria [109, 113] as well as spores that are resistant to high temperature and pressure [29]. ZnO-NP are also effective in inhibiting the growth of fungi (*Aspergillus flavus*, *A. ochraceus* and *A. niger*) and their mycotoxins production [114]. Some possible mechanisms of bactericidal action of metal oxide NP was generation of reactive oxygen species inside the bacterial cells (e.g., hydroxyl, hydroperoxide, and superoxide radicals) that may damage lipid membranes of cells and organelles of bacteria [109, 115] or they alter permeability of bacteria after entering their plasma membrane resulting in cell death [116]. They may damage bacterial cell after penetration by interacting with sulfur and phosphorus containing important compounds like DNA [113]. As per Rajendran et al. [117], ZnO NP inactivates the proteins that are responsible for transport of nutrients, thus decreasing the membrane permeability and eventually causing the cellular death. Another explanation about antimicrobial action of metal oxide NP is that microorganisms carrying a negative charge are electromagnetically attracted towards metal oxides carrying a positive charge, subsequently leading to oxidization and death of microbe [113]. The antibacterial activity depends on the size, with better result obtained with smaller size [118]. But, Arabi et al. [113] observed the significance of surface area and concentration of NP,

whereas crystalline structure and shape of NP have little significance.

**13. Environment implication of nanomineral supplementation**

In high intensified production system, trace minerals are added to poultry diets in high amounts exceeding the birds' requirements, with a large safety margin, creating environmental issues particularly in areas of intensive poultry production [8]. A study reported that by using poultry manure, Zn content in soil was found in excess by 660% in comparison to plant Zn requirements, predisposing to

**72**

FeO NP caused 100% mortality at 200 mg/L and decreased body weights and crown-rump lengths of embryo at 50 and 100 mg/mL and 50–60% degeneration of neurons in brain at 10–100 mg/L dose range [133]. It seems few minerals in their nanoforms are more toxic than their coarser forms. Therefore, safety and toxicity levels of different nanominerals should be widely evaluated before recommending them at an optimum dose for their use in poultry.
