*5.2. Poultry*

Typical poultry diets are commonly enriched by feed additives containing vitamins and minerals to support rapid growth and a favorable feed conversion ratio, and nanosized feed additives characterized by a high surface area to volume ratio and high absorption in the body could be incorporated in vaccines and nutrient supplements and directly transported to targeted organs or systems without degradation resulting in health benefits. Current state of NPs use as poultry feed supplements was reviewed by Gangadoo et al. [271].

AgNPs received in drinking water containing 1000 mg AgNPs/kg significantly reduced the body weights of the broilers after 42 days of administration, and this adverse effect could not be mitigated with a basal diet supplemented with Zn (60 and 120 mg/kg) and vitamin E ( α-tocopherol acetate; 100 and 200 mg/kg). On the other hand, the increased activity of CuZn-SOD observed in AgNPs-treated broilers was not recorded in birds fed with the basal diet supplemented with 200 mg/kg vitamin E, suggesting its antioxidant effect. Moreover, Zn supplementing enhanced catalase and GPx activities in the jejunal mucosa resulting in increased malondialdehyde (MDA) levels in the animals. Therefore, it could be concluded that the dietary Zn and vitamin E supplementation was able to attenuate intestinal oxidative stress in AgNPs-treated broiler chickens, although it did not mitigate the growth reduction caused by AgNPs [272]. In ovo feeding was found to reduce post-hatch mortality and skeletal disorders and increase muscle growth and breast meat yield. Sawosz et al. [273] used AgNPs as a protective carrier for adenosine triphosphate (ATP) as well as an active agent, which may penetrate tissues and cells and localize inside cells. They injected AgNPs, ATP, or a complex of AgNPs + ATP (AgNPs/ATP) in broiler eggs, and on day 20 of incubation, the embryos were evaluated. An increased expression of fibroblast growth factor 2, vascular endothelial growth factor, and Na+/K+ transporting ATPase were estimated at the application of ATP or AgNPs to chicken embryos. Moreover, AgNPs also upregulated the expression of myogenic differentiation 1, affecting cell differentiation. Based on the above-mentioned findings, it could be concluded that an extra energy source in the form of ATP addition enhanced molecular mechanisms of muscle cell proliferation, and ATP and AgNPs could accelerate the growth and maturation of muscle cells [273].

The in ovo injection of CuNPs using the dose of 50 mg/kg CuNPs improved broiler performance more efficiently than the injection of 50 mg/kg CuSO4 or the provision of CuNPs or CuSO4 in drinking water containing 20 mg/kg CuNPs or CuSO4 to growing chickens. In another experiment, which was carried out with 126 one-day-old broiler chickens from day 1 to 35 post-hatching, the in ovo application of Cu enhanced the final body weight, average daily gain, and feed conversion ratio compared to control animals and resulted in a considerable improvement in energy and nitrogen utilization, mainly for CuNPs application. The CuNPs treatment also reduced cholesterol, urea, and glucose levels in the blood [274]. The supplementation of a Cu deficient basal diet of chickens with CuNPs in drinking water to the level of Cu exceeding the National Research Council (NRC) recommendation by 54% resulted in the increased antioxidant potential of the organism and the inhibition of lipid peroxidation. Antioxidant and immune defenses of chickens were simultaneously increased in chickens receiving diet supplemented with CuNPs up to 12 mg per bird during 6 weeks of feeding, i.e., up to a level exceeding the NRC recommendation for growing broiler chickens at the most by 7%. It could be mentioned that at a higher CuNPs supplementation, a deterioration in red blood cell parameters and the stimulation of the immune system reflected in an increase in interleukin-6, immunoglobulin A (IgA), IgM, and IgY was observed [275].

The in ovo administration of NPs could be considered as a new method of nano-nutrition to supply an additional quantity of nutrients to embryos. ZnNPs, CuNPs and SeNPs supplemented in ovo at doses 20, 40, 60, and 80 μg ZnNPs/egg, 4, 8, 12, and 16 μg CuNPs/egg, and 0.075, 0.15, 0.225, and 0.3 μg SeNPs/egg (18th day incubation, amniotic route) did not show any adverse effect on the developing embryo and did not influence the hatchability, best feed efficiency being observed with 40 μg ZnNPs/egg, 4 μg CuNPs/egg and 0.225 μg SeNPs/egg. Moreover, the application of 12 μg CuNPs/egg resulted in considerably higher breast muscle percentage [276].

In white Leghorn laying hens (68-week old) receiving a diet supplemented with Zn-Met, bulk ZnO, and ZnO NPs reaching the level of 60 mg Zn/kg in the diet, pronouncedly higher Zn retention, serum GH concentration, and carbonic anhydrase activity were observed at the application of the ZnO NPs and Zn-Met compared to the control, and the ZnO NPs enhanced eggshell thickness as well [241]. Laying hens at 64 weeks of age fed with a basal diet supplemented with 80 mg/kg of bulk ZnO, ZnO NPs, and Zn-Met showed considerably higher egg production and egg mass as well as SOD activity in the liver, pancreas, and plasma when Zn-Met and the ZnO NPs were applied, while the greatest increase in eggshell thickness and shell strength was observed at the ZnO NPs application. The Zn supplementation resulted in reduced egg loss and lower MDA content and had a beneficial

effect on serum total protein, Alb, glucose, alkaline phosphatase activity, carbonic anhydrase activity, and Zn level, which was reflected in an improved performance of laying hens. Due to the enhanced Zn absorption in the intestine of aged layers at the application of ZnO NPs, they could be considered as a more suitable source of Zn in diets than bulk ZnO [277]. At the dietary supplementation of Zn-Met, ZnO, ZnO NPs or polyglutamic acid (PGA)–ZnO NPs reaching the level of 80 mg Zn/kg in the diet, increased Zn content in eggshells, serum Zn concentration, ghrelin and IgG levels of 64-week old brown layers were observed at the application of the ZnO NPs and the PGA-ZnO NPs, exceeding that observed at the application of bulk ZnO, and serum carbonic anhydrase activity and ghrelin levels were also increased compared to Zn-Met, suggesting that the ZnO NPs alone or in combination with PGA show beneficial impact on the Zn status of aged layers [278].

Investigation of the effects of SeNPs on performance, meat quality, immune function, oxidation resistance, and tissue Se content in broilers performed with 1-day old male Arbor Acres broilers showed that the supplementation of corn-soybean meal-based diets with 0.3–0.5 mg SeNPs/kg was found to be the best, and the maximum supplementation of SeNPs could not exceed 1.0 mg SeNPs/kg [279]. The adverse effects of oxidative stress in broiler chickens induced by *tert*-butyl hydroperoxide were attenuated when the animals received a diet supplemented with 0.3 mg SeNPs/kg. In stressed chicks fed with SeNPs, the heterophil:lymphocyte ratio was lower than in the groups, the diet of which was supplemented with bulk inorganic or organic Se, suggesting a higher effectiveness of SeNPs in the mitigation of oxidative stress [280]. Supplementation of SeNPs (0.1–0.5 mg/kg) in broiler diets could improve growth performance, carcass components, and immune function of the animals, and no adverse effects on internal organs, other carcass parameters, and GI parts were observed. SeNPs dietary supplementation resulted in significantly improved weight gain and feed conversion ratio during the whole period of experiment (42 days) and more efficient energy and protein utilization compared to the control group [281].

Rahmatollah et al. [282] reported that 1.2 mg/kg cysteine-coated Fe3O4 NPs were found to be required and sufficient for quails' optimal maintenance and growth suggesting that cysteine-Fe3O4 NPs can be used as a Fe source in the quail diet.

Cr utilization in 32 three-week-old broilers fed with a diet supplemented with Cr at the 1200g/kg level using CrCl3, chromium picolinate (CrPic), and CrPic NPs decreased as follows: CrPic NPs > CrPic > CrCl3 > control groups, and significant differences between individual groups were estimated. When one-day-old broilers were fed with diet supplemented with the above-mentioned Cr compounds, the feed intake of 4–5 weeks showed better results in the CrCl3 group compared to the CrPic group, while the LDL-cholesterol in the CrPic NPs groups was lower than in the CrPic group, and CrPic NPs and CrPic groups showed considerably enhanced serum Cr concentration compared to the control and CrCl3 groups. Based on the above results, it could be concluded that the CrPic NPs supplementation has advantages compared to the bulk CrPic supplementation, because it not only increases Cr utilization but also results in a lower serum LDL-cholesterol level in broilers [283].
