Growth performance
The results of the study indicated that body weight (Fig 1), cumulative body weight gain (Fig 2) and feed intake (Fig 3) of broiler chicken increased significantly (p<0.01) in the 50% nano group (T
4) when compared to other groups. Body weight gain in birds fed diets supplemented with zinc, manganese and copper in nano forms at 50% requirement level was increased around 10.21% when compared to control group (100% inorganic group).
Although 100% organic group (T
2) and 100% nano group (T
3) showed lesser growth and feed intake than the 50% nano group, these groups performed better when compared to 100% inorganic group (T
1) and 25% nano group (T
5). However, body weight gain in 100% organic group and 100% nano group were increased by 4.11% and 4.92%, respectively when compared to control group. Although the inclusion rate of Zn, Mn and Cu is reduced in 25% nano group, there was no significant difference between 25% nano group and 100% inorganic group in terms of growth performance. However, FCR and per cent livability did not vary significantly between the groups throughout the experimental period (Fig 4). Improvement in growth performance in T
4 (50% Nano) over other groups could be attributed to higher bioavailability of Zn, Mn and Cu at reduced inclusion levels and absence of negative interaction among minerals in GI tract. Further, on par growth performance recorded in T
5 (25% Nano) compared to control group (T
1-100% inorganic) might be due to the better bioavailability of nano minerals compared to their respective mega particles.
Similar results were observed by the other researchers and they reported that supplementation of nano forms of Zn, Mn and Cu resulted in higher body weight gain and feed intake in commercial broiler chicken when compared to their respective inorganic forms and organic forms
(El-Katcha et al., 2017; Alkhtib et al., 2020; Matuszewski et al., 2020). They also reported that there was no significant change in FCR.
The higher body weight gain observed in nano Zn, Mn and Cu supplemented groups might be due to increased absorption of nano Zn, Mn and Cu from GI tract. Because of smaller particle sizes of Zn, Mn and Cu nanoparticles, a faster diffusion might have occurred in GI tract to reach the intestinal lining. Nano particles with reduced size have greater surface area, thereby they exhibit a higher rate of absorption in the gastrointestinal tract
(Hussain et al., 2001). Nano-sized minerals distribute quickly from the circulation to the tissues and they are mostly targeted at organs with a well-perfused reticuloendothelial system (RES), such as the spleen and liver
(Geraets et al., 2014).
Serum antibody titers against NDV and IBDV
The results of the present study indicated that there was no significant difference between the treatment groups in antibody titer value against NDV after 14
th day of vaccination. After 28
th day of vaccination, the control groups had significantly higher titer values against NDV when compared to all the other groups (Fig 5).
The results of the present study were in accordance with
Sabaghi et al., (2021) who found that the nano manganese supplementation at 100 ppm and 150 ppm levels in broiler chicken showed reduced (p<0.05) antibody titer values against NDV when compared to the inorganic manganese supplementation.
Superoxide dismutase activity in serum
Superoxide dismutase activity in broiler chicken is influenced by the supplementation of different forms of Zn, Mn and Cu. In the present study, a significant increase in serum SOD activity was observed in 100% nano (T
3) and 50% nano (T
4) groups when compared to other treatment groups. However, no difference was observed between 100% inorganic group (T
1) and 25% nano group (T
5) (Fig 6).
Similar results of increased SOD enzyme activity in plasma were reported by
Abedini et al., (2018) with the ZnO nanoparticle supplementation in broilers when compared to the control group.
El-Kazaz and Hafez, (2020) concluded that broilers fed with copper nanoparticles have considerable increase (p<0.05) in serum copper and SOD levels compared to CuSO4 treated birds. It was reported that Zn, Mn and Cu nanoparticles were found to have higher bio-availability than their inorganic and organic counterparts because of their faster rate of absorption
(Jankowski et al., 2020).
Bioavailability of biomarkers of zinc, manganese and copper
The results of the present study indicated that the metallothionein gene expression in liver and muscle was higher in 100 and 50 % nano mineral supplemented groups when compared to other treatment groups (Fig 7). Similarly,
Varun et al., (2017) reported that the broiler chicken fed with nano zinc had relatively higher expression of metallothionein gene in liver when compared to inorganic zinc.
MnSOD mRNA levels in both liver and muscle were higher (p<0.01) in 100% and 50% nano mineral supplemented groups when compared to inorganic mineral supplemented group. Similarly,
Zhang et al., (2020) reported that the dietary supplementation of manganese improved the gene expression of MnSOD thereby increasing the intestinal immunity in broiler chicken.
Liver ceruloplasmin mRNA levels were not influenced by dietary copper supplementation of inorganic, organic or nano copper in broilers. Accordingly,
Scott et al., (2018) reported that ceruloplasmin mRNA gene expression was not affected by dietary source of copper in liver tissue of broiler chicken. Hence, liver ceruloplasmin mRNA expression might not be an efficient biomarker to indicate copper bioavailability. However, significant upregulation was observed in muscle ceruloplasmin mRNA expression when the birds are supplemented with organic and nano forms of copper at 100 and 50% requirement levels.
It was revealed from this study that the supplementation of nano forms of zinc and manganese upregulated the expression of metallothionein and MnSOD in liver and muscle tissue. Whereas, nano supplementation of copper upregulated the expression of ceruloplasmin in muscle tissue. These upregulation of biomarkers for zinc, manganese and copper indicated that the nano form of supplementation had increased the bio-availability of these three trace minerals in broiler chicken.