شریف رستمی

The effect of external heat stress on the oxidative stress genes in the liver and intestine of broiler chickens fed with silver nanoparticles coated on zeolite and organic acid was investigated.

450 one-day-old Cobb chicks were divided into 5 groups of 15, with 6 replicates of each group and kept for 42 days in the same rearing conditions. 1) Control (basal diet), 2) A base diet with 1% zeolite, 3) A basic diet supplemented with 0.5% nanosilver-coated clinoptilolite at 1%, 4) A base diet with 0.15% organic acid, and 5) A base diet with 1% zeolite covered in 0.5% nanosilver and 0.15% organic acid.  The heat stress (34±1˚C temperature for 6 hours per day) was provided from 35th to 42th days. To examine antioxidant enzymes gene expression on day 42, liver and intestinal samples were taken.

In treated groups, the relative expression of the liver SOD gene was not significantly different compared with control group (P>0.05), whereas in all treatment groups SOD and glutathione peroxidase (GPX) expression had shown decrease in the intestine compare to control group (P<0.05). In group treated with zeolite coated with nanosilver and an organic acid, the relative expression of the catalase (CAT) gene showed decrease while it increased in group treated with a basal diet.

It was observed that the intestine has higher levels of antioxidant enzymes activity compared to the liver. Also, to increase the growth efficiency, it is preferred to use the combination of silver nanoparticles with organic acids.

Due to the ban on the use of antibiotics as a growth promoter in the broiler industry since 2007, researchers are always looking for a suitable alternative to antibiotics. Silver nanoparticles with antibacterial, antifungal and antiviral properties were used as one of the proposed alternatives to antibiotics and the purpose of this study was to evaluate the effect of coated silver nanoparticles on zeolite on the expression of metallothionein gene as a biomarker of heavy metals in the liver cells of broiler chickens.

In this experiment, Ross 308 broiler chickens were allocated to five experimental diets: control or basal diet, basal diet supplemented by 1% zeolite, basal diet supplemented by 1% zeolite coated with 0.5% nanosilver, basal diet supplemented by 0.15% organic acid and basal diet supplemented by 1% zeolite coated with 0.5% nanosilver and 0.15% organic acid were designed under normal and heat stress conditions. Liver tissue samples were collected on days 21 and 42 of rearing period. In order to perform gene expression studies, RNA was extracted and its quality was evaluated by electrophoresis and after purification, cDNA synthesis was performed. In the following the polymerase chain reaction was performed for tissue cDNA samples for metallothionein gene and also betaactin as reference gene.

The results showed a significant increase in expression of metallothionein gene in the liver tissue of broilers in zeolite treatment on d 21 (p<0.05). Also, on d 42 of rearing period without heat stress conditions, a significant increase in metallothionein gene expression were observed on silver nanoparticles coated on zeolite and 0.15% organic acid (NSOA) treatment. Also, on d 42 under heat stress conditions the results showed a significant increase in zeolite (Z) and silver nanoparticles coated on zeolite (NS) treatments in liver tissue in comparison with control treatment (p<0.05).

The results of present study indicated that metallothionein gene could be considered as a reliable heavy metal biomarker under normal and heat stress conditions in broiler chickens.

In order to evaluate the effect of silver nanoparticles coated by clinoptilolite on cytochrome P450 gene expression in broiler chicken’s liver an experiment consisting of (1) control diet, (2) clinoptilolite, (3) clinoptilolite coated with silver nanoparticles, (4) organic acids and (5) clinoptilolite coated with silver nanoparticles and organic acids in normal and heat stress conditions was designed. Liver biopsy was obtained on 21 and 42 days of experiment. Results of this study demonstrated there were no interaction between experimental treatments and heat stress conditions in chickens. As well as the expression levels of  both isoforms of CYP450 gene  in clinoptilolite treatment on day 21 and silver nanoparticles coated on clinoptilolite with organic acid treatment on day 42 of experiment in normal conditions, were significantly increased in comparison with control treatment (C) in chicken liver tissue (P<0.05). Level of CYP2C18 on  day 42 of experiment in heat stress condition in silver nanoparticles coated on clinoptilolite treatment was significantly increased in comparison with control (C) treatment (P<0.05). Whereas, the level of CYP2C23b gene expression on day 42 of experiment was not significantly different with control treatments (P>0.05) in heat stress conditions. In conclusion, results showed that the expression level of CYP2C18 isoform in liver tissue of broiler chickens was higher in comparison with CYP2C23b isoform.  The liver, as a metabolism organism in the body, identified clinoptilolite and silver nanoparticles as inorganic, chemical and exogenous substances and increased the expression level of cytochrome P450 gene acts as a biomarker for the existence of exogenous and inorganic substances in the body.

Nowadays, researchers are converted silver to nanometer dimensions and using nanotechnology to achieve suitable performance and preserve the poultry health and they are used silver nanoparticles are used for poultry nutrition as a nutritional supplement. On the other hand, at the molecular level no complete reports in poultry breeding have been provided.

This study was conducted to evaluate cytochrome P450 gene expression in broiler chickens fed with silver nanoparticles.

This experiment a completely randomized design with 450 single-day Cobb 500 broiler chicks was divided into five treatments and six replications (15 birds in each replicate). Chickens were fed with (1) control (basal diet), (2) basal diet containing 1% zeolite, (3) basal diet containing 1% of zeolite-coated with 0.5% silver nanoparticles, (4) Basal diet containing with 0.15% organic acids and (5) Basal diet containing 1% of zeolite-coated with 0.5% of silver nanoparticles and 0.15% organic acids in with or without heat stress condition.

Results demonstrated the level of expression of cytochrome P450 in broilers fed zeolite (Z) in the 21st day of experiment, silver nanoparticles coated with zeolite in combination with organic acid (NSOA) in 42nd day without heat stress condition and silver nanoparticles coated with zeolite (NS) in day 42 with heat stress condition in intestine and liver had significant increase in expression in comparison with control (C) treatment (P<0.05).

In conclusion, result showed that zeolite and silver nanoparticles were identified as inorganic, chemical and exogenous substances in liver and intestine and up-regulated expression of pollution biomarkers genes. Whereas this effect is not identified in organic acid.

Heat stress is one of the most important immunosuppressive factors in poultry industry and heat stress has been associated with increases reactive oxygen species and oxidative stress in cells. Since the nuclear factor kappa-B is known as fast cellular response factor to endogenous stress; this study was conducted to evaluate relative gene expression in broiler chicken with 450 one-day-old Cobb 500 broiler chickens for 42 days. Treatments included: (1) basal diet (control), (2) basal diet containing 1% zeolite, (3) basal diet containing 1% of zeolite-coated with 0.5% silver nanoparticles, (4) Basal diet containing with 0.15% organic acids and (5) Basal diet containing 1% of zeolite-coated with 0.5% of silver nanoparticles and 0.15% organic acids in with or without heat stress condition. Liver biopsy was done in 21st and 42nd days of experiment. Results demonstrated the level of nuclear factor kappa-B relative gene expression in the 21st and 42nd days of experiment with heat stress condition in zeolite treatment and 42nd days of experiment without heat stress condition in silver nanoparticles coated with zeolite in combination with organic acid in broiler liver was significant increase expression comparison with control and all treatments (P<0.05). In conclusion results showed that zeolite and silver nanoparticles identified as an inorganic, chemical and exogenous substances in body tissues and liver identified this substances as a xenobiotics and up-regulated expression of index genes in oxidative stress pathways and inflammation. Whereas this effect is not identified in organic acid.

The aim of this experiment was to study the effects of long-term induced hyperthyroidism on the body weight and egg production. In addition the relationships between hyperthyroidism and some reproductive parameters were studied. A total of seventy 47-week-old Cobb 500 breeder hens were randomly allotted to two treatment groups (5 replicates of 7 hens each). Thyroxine was orally administered to the hyperthyroid group (0.3 mg/bird/day) for 100 consecutive days during which the body weight and egg production were recorded on a weekly basis. Effect of hyperthyroidism on plasma T4 levels was significant; but, the T3 level was not affected. Results indicated a significant decreasing effect of thyroid hormones on body weight. Thyroid hormones had no effect on egg production; however, the treatment × time (wk) interaction effect was significant on egg production. Ovarian and oviductal weight were not different between the control and hyperthyroid hens. Administration of thyroxine to breeder hens decreased the diameter of F1 follicles.