| This study was conducted to investigate the effect of different sources and levels of Se on the broiler breeders and their progeny and it also revealed the mechanism of the regulation of chick embryo mortality by different sources of Se via investigating the effect of maternal Se on the mortality and antioxidative capacity of the developing chick embryo and the protective effect of maternal Se in oxidative-stressed chick embryo, in order to uncover the main function and mechanism of SM.Experiment1Effect of different sources and levels of selenium on the broiler breeders and their progenyA3×2completely random design was employed in this trail,3sources and2levels of Se. A total of540healthy48-week-old Lingnan Yellow broiler breeders were assigned to6treatments with3replicates (30birds per replicate). The feeding experiment lasted for8weeks after2weeks of adaptation period. The Se concentration of BD is0.04mg/kg. Fertilized eggs were collected during the last week of the experimental period and stored under18℃and then incubated under normal hatchery management. After hatching,601-day-old chicks form each replicate were collected and raised replicatedly. All of the chicks were fed with the same commercial feed containing Se at a level of0.15mg/kg. At the end of the feeding experiment of the breeders and their progeny and the incubation, breeders and their progeny were slaughtered and samples were collected for analysis. The results showed that:(1) Compared with the Se level of0.30mg/kg,0.15mg/kg significantly (P<0.05) increased the hatchability of fertilized eggs and had an increasing trend in birth rate (P<0.1). No differences were found in reproductive performances of the breeders between different sources of Se treatments (P>0.05). However, the highest laying rate, fertility, hatchability and birth rate were all found in0.15mg/kg SM treatment. (2) Compared with SS, adding SM and/or SY in the diets remarkably (P<0.05) elevated the Se concentrations of the breeders, fertilized eggs, developing chick embryos and1-day-old chicks. Compared with SY, SM notably (P<0.05) increased the Se concentrations of the breeder serum, fertilized eggs and the kidney and muscle of1-day-old chicks. The Se level of0.30mg/kg was superior to0.15mg/kg in Se retention (P<0.05).(3) Compared with SS, the usage of SM and/or SY significantly (P<0.05) improved CAT activity and T-AOC in the liver and kidney of breeders and CAT activity in the kidney of1-day-old chicks. It also decreased MDA concentration in the kidney and pancreas of breeders and liver of1-day-old chicks (P<0.05). Compared with the Se level of0.30mg/kg,0.15mg/kg remarkably increased the breeder serum GPx activity, breeder kidney T-SOD activity and the T-AOC in the serum, liver and muscle of breeders (P<0.05). It also elevated the liver GPx activity, T-SOD activity and T-AOC and kidney T-SOD activity, CAT activity and T-AOC in1-day-old chicks (P<0.05). The kidney MDA concentration of1-day-old chicks was decreased by the Se level of0.15mg/kg (P<0.05).(4) Compared with SS, adding SM in the feed significantly reduced feed/gain ratio of the21-day-old progeny (P<0.05). No differences in production performance of the56-day-old progeny were found between treatments (P>0.05). There is a decreasing trend in feed/gain ratio of the56-day-old progeny in SM treatment when compared with SS treatment (P<0.1).(5) No differences in carcass traits of the progeny were found between treatments (P>0.05). Compared with SS and SY, SM notably (P<0.05) improved liver index and breast muscle16-hour pH value of the progeny. Se level of0.15mg/kg increased liver index, breast muscle8-hour Hunter a value and breast muscle pH value of the progeny (P<0.05) and reduced drip loss (P<0.05).(6) Compared with SS, adding SM and/or SY in the diets remarkably (P<0.05) elevated GPx1mRNA level, TrxR1mRNA level and activity and Se1P mRNA level and protein concentration in the liver of breeders. It also increased GPxl, TrxR1and SelP mRNA level and activity or protein concentration in the liver of1-day-old chicks (P<0.05) and activity or protein level in the kidney of1-day-old chicks (P<0.05).This experiment indicates that SM has the highest value among the3sources of Se in improving reproductive performance, Se retention and antioxidative capacity of the broiler breeders and the early production performance of the progeny. When using SM, a Se level of0.15mg/kg is recommended.Experiment2Effect of different sources maternal selenium on the mortality and antioxidative capacity of the developing chick embryoThis trail was to investigate the effect of different sources maternal Se on the mortality and antioxidative capacity of the developing chick embryo. A total of270healthy40-week-old Lingnan Yellow broiler breeders were randomly assigned to3treatments with5replicates per each. Breeders were fed with BD supplemented with SS or SM at Se level of0.15mg/kg, using BD (Se level,0.04mg/kg) as a control. The feeding experiment lasted for8-week after2-week of adaptation period. Fertilized eggs were collected during the last7-day of the experimental period and stored under18℃and then incubated under normal hatchery management. During hatching, developing chick embryos at different embryonic ages (9,14,19and21-day) were slaughtered and samples were collected for analysis. The results showed that:(1) The early, middle, late and whole period mortality of the developing embryo were lower in SM and SS treatments than that of BD treatment (P<0.05). Compared with SS, SM decreased the mortality of the developing embryo (P<0.05).(2) Supplementation of maternal diet with SM and/or SS notably (P<0.05) enchanced GPx, T-SOD and CAT activity and T-AOC and reduced MDA and ROS concentrations.(3) Compared with SS, SM remarkably (P<0.05) improved T-AOC and T-SOD and CAT activity in the developing chick embryo at embryonic day19and/or21and decreased MDA and ROS concentrations in the developing chick embryo at embryonic day19and21.(4) Compared with BD, adding SM and/or SS in the feed significantly elevated GPx1mRNA level and activity and TrxR1activity in the developing chick embryo at embryonic day14,19and21and TrxRl mRNA level at embryonic day19and21(P <0.05). SelP mRNA and protein expression were also upregulated by supplementation of SM and/or SS (P<0.05).(5) Supplementation of SM in the diet upregulated GPx1, TrxR1and SelP mRNA level and activity or protein level when compared with SS (P<0.05).This trail indicated that maternal Se is essential for maintaining the normal development and antioxidative capacity of the chick embryos. During the late period of incubation, SM had a better effect than SS.Experiment3Establishing of the oxidative stress models of chick embryoA total of1000fertilized eggs from parental Lingnan Yellow broiler breeders were allocated into5treatments with5replicates per each. On embryonic day17, eggs were heated at37.5(control),38.5,39.5,40.5and41.5℃respectively for6hours. The results from this experiment revealed that ROS and HSP70concentrations and the antioxidant index were changed significantly (P<0.05) while no differences were found in the mortality of chick embryo (P>0.05) when the stimulating temperature reached39.5℃, which indicates that the oxidative stress model of chick embryo was successfully established.Experiment4The protective effect different sources of maternal selenium on oxidative stressed chick embryoTreatmens and feeding of the broiler breeders were the same as that of experiment2. Fertilized eggs were collected during the last7-day of the experimental period and stored under18℃. On embryonic day17,20eggs were collected from each replicates and transferred into another incubator and heated at39.5℃for6hours. After stimulating,5eggs with or without heating from each replicate were slaughtered and samples were collected for analysis. The results showed that:(1) Supplementation of SM and/or SS in the feed resulted lower ROS, MDA, carbonyl and8-OHdG concentrations and apoptosis index and higher GPx, T-SOD and CAT activity when compared with BD (P<0.05). (2) Under oxidative stress condition, ROS, MDA, carbonyl and8-OHdG concentrations were lower in SM treatment than that in SS treatment (P<0.05).(3) Compared with BD, SM and/or SS notably (P<0.05) elevated GPxl mRNA level and activity, TrxRl activity and SelP mRNA and protein level in non-stressed chick embryo and TrxRl and SPS1mRNA levels in stressed chick embryo.(4) Under oxidative stress condition, SM showed a higher value than SS in upregulating GPxl, TrxRl and Se1P mRNA level and activity or protein level and SPS1mRNA level (P<0.05).This experiment indicates that through regulating the expression of selenoprotein, maternal Se can enhance antioxidative capacity, reduce ROS concentration, oxidative damage and apoptosis in chick embryo and then mortality of the chick embryo is decreased. Moreover, SM is superior to SS under oxidative stress condition, which could be the possible mechanism of improving surviving of chick embryos by maternal Se. |
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