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This study investigated the effect of nano-selenium (nano-Se) in protecting laying hens from mercury (Hg)-induced prehierarchical follicular atresia. Furthermore, the endoplasmic reticulum stress (ERS) was explored to reveal the molecular mechanism. In vivo, 720 Hyline-Brown laying hens were treated with Hg and nano-Se alone or in combination. In vitro, the prehierarchical follicles were treated with Hg, nano-Se and 4-phenyl butyric acid (4-PBA) alone or in combination (Control, 25 μM Hg group, 10 μM nano-Se group, 20 μM nano-Se group, 25 μM Hg + 10 μM nano-Se group, 25 μM Hg + 20 μM nano-Se group, 25 μM Hg + 4-PBA group, and 25 μM Hg + 20 μM nano-Se + 4-PBA group). The GCs were treated with Hg and nano-Se alone or in combination (Control, 15 μM Hg group, 6 μM nano-Se group, 12 μM nano-Se group, 15 μM Hg + 6 μM nano-Se group, 15 μM Hg + 12 μM nano-Se group). The results revealed that dietary Hg significantly reduced laying performance (P0.05) and egg quality (P0.05), whereas nano-Se addition prevented these reductions (P0.05). Hg exposure significantly induced the accumulation of Hg in PHFs (P0.05), prehierarchical follicular atresia (P0.05) and apoptosis in PHFs, whereas nano-Se addition significantly prevented these effects (P0.05). The levels of sex hormones (P0.05) were significantly decreased after Hg exposure in vivo and in vitro, while nano-Se addition prevented the reductions. Furthermore, the RNA-Seq results showed that the key factors of the ERS presented differential expression, including C/EBP homologous protein, protein kinase RNA-like endoplasmic reticulum kinase (PERK) and activating transcription factor 6 (ATF6) in GCs. Hg exposure significantly increased the key gene expression of endoplasmic reticulum stress in GCs, whereas nano-Se addition prevented the induction of expression of these genes. In addition, the protein levels of PERK, inositol requiring protein 1α (IRE1α) and ATF6 were significantly increased, whereas nano-Se addition prevented the enhancements of protein expression in GCs. In conclusion, this study shows that Hg exposure can reduce induce prehierarchical follicular atresia, whereas nano-Se can prevent these effects. Our results also elucidate a key role of ERS in these protective effects of nano-Se in laying hens.

This study investigated that the effect of nano-selenium (nano-Se) addition preventing prehierarchical follicular atresia induced by mercury (Hg) exposure in laying hens. Furthermore, endoplasmic reticulum (ER) stress pathway was explored to reveal the protective mechanism of nano-Se in vitro. The results revealed that Hg could significantly reduce laying performance (P 0.05) and egg quality (P 0.05), whereas nano-Se addition partially reversed the reductions. Besides, Hg significantly induced the deposition of Hg in prehierarchical follicles (P 0.05) and prehierarchical follicular atresia (P 0.05), whereas nano-Se addition could alleviate these toxicities in vitro. In addition, Hg exposure could significantly reduce cell viability (P 0.05) and induce pyknotic nucleus in prehierarchical granulosa cells, while nano-Se addition reversed these effects. The levels of follicle-stimulating hormone (P 0.05), luteinizing hormone (P 0.05), progesterone (P 0.05), and estradiol (P 0.05) were significantly decreased after Hg exposure in vitro. However, nano-Se addition reversed the decreases of sex hormone levels. Furthermore, Hg exposure significantly increased the gene expressions of CHOP (P 0.05), PERK (P 0.05), ATF4 (P 0.05), ATF6 (P 0.05), ASK1 (P 0.05), IRE1α (P 0.05), TRAF2 (P 0.05), caspase-9 (P 0.05), caspase-3 (P 0.05), and Bax/Bcl-2 (P 0.05), whereas nano-Se addition reversed these increases of gene expressions in vitro. In summary, this study provides that Hg can induce prehierarchical follicular atresia, whereas nano-Se addition can ameliorate it, and elucidates an important role of ER stress in nano-Se alleviating prehierarchical follicular atresia induced by Hg in laying hens.

The objective of this study was to compare the effects of natural clinoptilolite and modified clinoptilolite on growth performance and antioxidant capacity in broiler chicks. Two hundred forty 1-day-old commercial Arbor Acres broilers were randomly distributed into three treatments, each of which had eight replicates. Each replicate contains 10 chicks. Control (CON) group fed with the basal diets, natural clinoptilolite (NCLI) group fed basal diets with 2 % natural clinoptilolite, and modified clinoptilolite (MCLI) group fed basal diets with 2 % modified clinoptilolite for 42 days. The results showed that the 2 % supplementation of natural clinoptilolite and modified clinoptilolite had no adverse effect on growth performance of broilers at 42 days of age. Relative weights of organs were not influenced by dietary treatments at 21 and 42 days. The activity of total nitric oxide synthase was significantly (P < 0.05) decreased in MCLI group than CON group at 21 days of age. At 21 and 42 days, the activities of glutathione peroxidase, catalase, total superoxide dismutase, total antioxidant capacity (T-AOC) were significantly (P < 0.05) increased in NCLI and MCLI groups than the CON group while there was no difference in T-AOC between CON and NCLI groups. The malondialdehyde content was significantly (P < 0.05) decreased in NCLI and MCLI groups than the CON group. It was concluded that the addition of 2 % natural clinoptilolite and modified clinoptilolite to diet can improve antioxidant capacity in broilers, although their effects on growth performance was negligible.