| Zearalenone(ZEA)is a mycotoxin with estrogenic activity and many toxic effects.It is one of the most common mycotoxins in pig feed.Most agricultural areas in China have monsoon climate,so China’s ZEA pollution situation is serious.The ZEA contamination is widespread and occurs periodically with seasonal variations,continuing to harm the feed industry and the pig industry.In order to deal with the harm of ZEA pollution,relevant personnel have made a lot of efforts in the production of feed raw materials,feed processing,application and development of mildew preventive,toxin detection and poisoning treatment,but the harm of ZEA has not been effectively controlled.The reason lies in the lack of relevant mechanism research,which restricts the formulation of effective prevention and treatment measures.The hypothalamic-pituitary-gonadal axis(HPGA)is a complete neuroendocrine regulatory system,which plays an important regulatory role in the development of reproductive organs and reproductive activities of prepubertal gilts.The uterus is an important reproductive organ of prepubertal gilts and is closely related to the reproductive ability of prepubertal gilts.However,there are few reports on the effect of ZEA on HPGA and uterus.2 months old sows with the highest sensitivity to ZEA were selected for this study.In this study,the toxicity and related mechanisms of ZEA on HPGA and uterus of prepubertal gilts were studied by feeding the feed containing different ZEA levels.A total of 48 2 months old Landrace × Yorkshire sows with similar litter times,breeds and weight(23.20± 0.68 kg)were randomly divided into 4 groups(12 replicates per group,1 gilt per replicate).Prepubertal gilts in control group(CON group)were fed a basal diet and those in experimental groups(T1,T2 and T3 groups)were fed test diets supplemented with 200,800 and 1600 μg/kg ZEA in the basal diet.Pretest lasted 7 d,and test lasted 40 d.The results showed as follows.ZEA had no significant effect on ADG,ADFI,F/G,diarrhea rate,and the organ index of liver,kidney,spleen and thymus of prepubertal gilts(P>0.05).ZEA can make the vulva area of the prepubertal gilts in the test groups increase significantly(P<0.05)or extremely significantly(P<0.01).This indicated that ZEA treatment produced obvious reproductive toxicity to the prepubertal gilts.We can conduct further research.It was found in this experiment,the digestibility of prepubertal gilts to crude protein significantly decreased(P<0.05),the digestibility to phosphorus very significantly decreased(P<0.01),and the digestibility to calcium significantly increased(P<0.05).Also found ZEA can significantly reduce the serum IgG and IgM levels of prepubertal gilts(P<0.05).Therefore,ZEA can indirectly affect the function of HPGA and uterus by affecting the digestibility of reserve sows to crude protein,phosphorus and calcium and decreasing immunity,thus playing a toxic role.ZEA can increase the uterine index of prepubertal gilts significantly(P<0.05)or significantly(P<0.01),and the ovarian index has an upward trend.After paraffin sections and HE staining,it were observed that ZEA can promote the development of secondary follicles in prepubertal gilts,making the follicles dilate and increase in size and can cause the endometrium and myometrium to thicken,with more glands and more density.Further fluorescence quantitative PCR,immunohistochemistry and western blot analysis revealed that ZEA can increase the expression levels of Ghrelin,GHR,PCNA mRNA and protein in ovary and uterus to accelerate the development of ovary and uterus.ZEA can significantly up-regulate the expression levels of kiss-1,GPR54,GnRH,GnRHR,ER,LHR and FSHR mRNA(P<0.05),and significantly down-regulate the expression levels of LH and FSH mRNA(P<0.05),which disrupt hormone secretion.ZEA can significantly increase the level of GnRH in serum and hypothalamus(P<0.05),significantly reduce the level of PROG in serum and ovary(P<0.05),significantly reduce the level of LH and FSH in serum(P<0.05),and significantly decrease the level of E2 first(P<0.05),and then significantly increase the level of E2(P<0.05),which disrupt hormone secretion.Combined with effects on ovaries,uterus,and vulva,ZEA treatment may cause reserve sows to exhibit a more complex reproductive toxicity similar to that of central sexual precocity.After paraffin sections and HE staining,also found in the T2 and T3 groups,there were also increased atretic follicles,inflammatory infiltration,and granulosa cell necrosis and there were focal lymphocyte infiltration,epithelial cell degeneration and necrosis,and cytoplasmic vacuolization of necrotic cells.In this study,the effects of ZEA on HPGA,uterine antioxidant system and inflammatory system were analyzed to explore the relevant mechanism.We found that ZEA can reduce the antioxidant performance of uterus and ovaries of gilts by inhibiting the expression and synthesis of SOD and GSH-Px,and causes oxidative stress in both tissues and pituitary gland and can induce inflammatory responses in the ovaries and uterus by promoting TNF-α and IL-1β expression and synthesis.ZEA can inhibit the anti-inflammatory response of ovaries and uterus by inhibiting the expression and synthesis of IL-10.ZEA also significantly or significantly up-regulated the relative expression levels of Hsp70 mRNA in ovary and uterus.This suggests that the pathological changes of ovary and uterus may be the result of the combined effect of oxidative stress and inflammatory response caused by ZEA.ZEA treatment can affect the microbial flora of the cecum of the prepubertal gilts,increasing the relative abundance and decreasing the diversity of T1 group,and increasing the relative abundance and diversity of T2 and T3 groups.Further analysis of microbial composition at the level of phylum and genus were found that ZEA treatment did not alter the major flora structure of the cecum of the prepubertal gilts.However,at the level of phylum,the relative abundance of Actinobacteria very significantly decreased(P<0.01),and that of Proteobacteria and Cyanobacteria very significantly increased(P<0.01).At the level of genu,the relative abundance of Streptococcus,Prevotellaceae_NK3B31_group and Alloprevotella increased significantly(P<0.05)or very significantly(P<0.01),and the relative abundance of Megasphaera and Faecalibacterium decreased significantly(P<0.05).The RDA method was used to preliminarily analyze the relationship between the change of cecum microflora diversity and the changes of vulva area,ovary and uterus index,reproductive hormone level,antioxidant enzyme activity and inflammatory factor level in prepubertal gilts treated with ZEA.We found that The area of vulva,ovary and uterine index were positively correlated with the relative abundance of Bacteroidetes and Firmicutes,and negatively correlated with the relative abundance of Proteobacteria and Chlamydiae.The levels of GnRH,LH,FSH and E2 were positively correlated with the relative abundance of Bacteroidetes,while the levels of PROG were negatively correlated with Bacteroidetes.The activities of T-AOC,GSH-Px and SOD were positively correlated with the relative abundance of Actinobacteria,Proteobacteria,Fusobacteria,and Chlamydiae,and negatively correlated with the relative abundance of Bacteroidetes,Firmicutes,Saccharibacteria,and Tenericutes.The levels of TNF-α,IL-1β,and IL-4 were positively correlated with the relative abundance of Bacteroidetes,Spirochaetae,and Tenericutes,while the levels of il-10 were negatively correlated with these bacteriums.In summary,in this experiment,ZEA treatment can directly exert toxic effects by regulating the expression of HPGA and utero-related genes and proteins in prepubertal gilts,causing endocrine disorders,oxidative stress and inflammatory reactions,accelerating the development of ovaries and uterus and causing pathological changes.It can also affect the digestibility of crude protein,phosphorus and calcium,reducing the level of IgG and IgM,affecting the diversity of cecum microflora,and indirectly playing a toxic effect. |
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