| Prolonged raise time decreased the laying performance of broiler breeders,egg quality and the growth performance of progeny chicks.As one of the key factors affecting the quality of eggs,prolonged egg storage time decreased the hatchabililty,chick quality and progeny growth performance.Oxidative stress appears to be a potential factor that caused higher mortality of embryos in long-term egg storage.Vitamin E(VE)plays a vital role in preventing oxidative damage.In this study,three experiments were conducted to investigate the effects of broiler breeder dietary VE supplementation on laying performance,egg quality and progeny growth performance,and further investigate the effects of broiler breeder dietary VE levels and egg storage time and their mechanisms of action on hatchability.Exp.1.Effects of dietary VE supplementation on laying performance and antioxidant status of broiler breeder hensExp.1-1 and 1-2 were carried out in the present study.In Exp.1-1,a total of 512 Ross 308 broiler breeder hens(71-wk-old)were allocated into 2 dietary VE treatments(6 and 100 mg/kg)with 8 replicates of 32 hens for 13 wk.Results showed that dietary VE supplementation did not affect the laying performance(P > 0.05).Dietary VE(100 vs.6 mg/kg)increased the ovarian T-SOD activity and T-AOC(P < 0.05),and decreased the ovarian MDA content(P < 0.05).In Exp.1-2,a total of 576 Ross 308 broiler breeder hens(75-wk-old)were allocated into 3 dietary VE treatments(100,200 and 400 mg/kg)with 6 replicates of 32 hens for 12 wk.Dietary VE supplementation did not affect the laying performance(P > 0.05).Serum T-AOC was higher in 400 compared to 100 and 200 mg/kg VE groups(P < 0.05),and ovarian MDA content was lower in 200 compared to 100 mg/kg VE groups(P < 0.05).In conclusion,taking laying performance as response criteria,the recommended level of 6 mg/kg VE by NRC(1994)could meet the requirement of broiler breeder hens beyond 70 wk.Increasing dietary VE(100,200 and 400 mg/kg)levels did not affect the laying performance of broiler breeder hens beyond 70 wk.And,consider the ovary antioxidant status of hens,the suitable VE concentration in breeder hen diet is at least 100 mg/kg.Exp.2.Effects of broiler breeder dietary VE suplementation and egg storage time and their mechanisms of action on the quality of eggsExp.2-1 and 2-2 were carried out in the present study.Exp.2-1 was conducted using a 2 × 2 factorial arrangement with two maternal dietary VE levels(6 or 100 mg/kg)and two egg storage times(stored 0 or 14 d)with 6 replicates per treatment at weeks 8,10 and 12 of Exp.1-1.The storage temperature for eggs stored 14 d were different,with 22-24 ℃ for 1-14 d at week 8,22-24 ℃ for 1-7 d and 16-18 ℃ for 8-14 d at week 10,and 16-18 ℃ for 1-14 d at week 12.Prolonged egg storage time(14 vs.0 d)decreased the egg characteristics and yolk T-AOC(P < 0.05);decreased the hatchability of set/fertile eggs,chick weight,health chick ratio and health chick number per hen(P < 0.05);decreased the chick brain MDA content and T-AOC at weeks 10 and 12(P < 0.05);increased the egg weight loss during storage and embryonic mortality between day 1-7 and 15-21.5 of incubation(P < 0.05);increased the chick serum,brain and yolk sac MDA content and T-AOC(P < 0.05)at week 8;increased the chick serum MDA content and T-AOC;and increased the chick serum T-AOC and yolk MDA content(P < 0.05).Dietary VE levels(100 vs.6 mg/kg)increased the yolk α-tocopherol and T-AOC(P < 0.05);increased the hatchability of set/fertile eggs(P < 0.05);increased the chick serum and yolk sac T-SOD activity and T-AOC(P < 0.05);decreased the embryonic mortality between day 1-7 of incubation(P < 0.05);decreased the yolk and the chick serum,brain and yolk sac MDA content(P < 0.05).Compared to unstored eggs,increasing dietary VE levels present positive effect in the improvement of hatchability and antioxidant status of chicks derived from eggs stored for 14 d.Further investigation indicated that prolonged egg storage time decreased the weight of embryo at day 3 and 7 of incubation(P < 0.05);increased the T-AOC of 7-d-old embryo(P < 0.05);increased the ROS content of 3-and 7-d-old embryo(P < 0.05);and increased the cell apoptosis of 3-and 7-d-old embryo and chick liver and brain(P < 0.05).Increasing dietary VE levels decreased the MDA content of 7-d-old embryo(P < 0.05);decreased the ROS content of chick liver and brain(P < 0.05);and decreased the cell apoptosis of 3-and 7-d-old embryo and chick liver and brain(P < 0.05).Compared to unstored eggs,increasing dietary VE levels present positive effect in the reduction of MDA content of 7-d-old embryo and cell apoptosis of chick liver hatched from stored eggs.The result of embryonic transcriptome demonstrated that the effect of maternal VE levels and egg storage time on the embryonic mortality is related to the pathways involved in oxidative stress,cell apoptosis,cell proliferation and differentiation,and embryonic development.The results of functional gene enrichment and gene m RNA expression indicated that maternal VE supplementation and egg storage time could individually or interactively regulated the expression of oxidative stress-related gene Ogg1,Gst,Sod3,Selenop1,Mt3,Pon2 and Nrf2;and the expression of cell apoptosis and proliferation and and embryonic development-related gene Col6a、G0s2、Wnt11、Bok、Casp3、Bax、Bcl2 and Hspb8.The eggs used in Exp.2-2 were collected at week 9(unstored)and week 12(stored with 16-18 ℃ for 14 d)of Exp.1-2.The egg incubation were both conducted with three treatments(maternal dietary VE 100,200 and 400 mg/kg).Results showed that as maternal dietary VE levels increased,the yolk α-tocopherol and T-AOC increased and MDA content decreased(P < 0.05).As eggs were stored for 14 d,increasing maternal dietary VE levels increased the hatchability of set/fertile eggs and health chick number per hen,and the chick tissue T-AOC(P < 0.05);decreased the embryonic mortality between day 1-7 of incubation,the MDA content of 7-d-old embryo and chicks(P < 0.05).In conclusion,prolonged egg storage time(14 vs.0 d)could suppress the development of embryo and decrease the hatchability and antioxidant status of egg yolks,embryos and newly hatched chicks.Increasing maternal dietary VE supplementation could alleviate these adverse influences induced by long-term egg storage.The effect of maternal VE levels and egg storage time on the embryonic mortality is related to the pathways involved in oxidative stress,cell apoptosis,cell proliferation and differentiation,and embryonic development.The oxidative stress-related gene Ogg1,Gst,Sod3,Selenop1,Mt3,Pon2 and Nrf2;and cell apoptosis and proliferation-related gene Col6a、G0s2、Wnt11、Bok、Casp3、Bax、Bcl2 and Hspb8 were the key genes in the process of VE alleviating these adverse influences induced by long-term egg storage.Taking hatchability as response criteria,the requirement of NRC(1994)meet the need of unstored egg incubation,however,the suitable VE concentration in breeder hen diet is at least 200 mg/kg after egg storage.Exp.3.Effects of broiler breeder dietary VE supplementation and egg storage time on the growth performance and antioxidant status of progeny chicksExp.3-1,3-2,3-3,3-4 and 3-5 were included in the present study.Exp.3-1 was conducted by a 2 × 2 factorial arrangement with two levels of maternal dietary VE levels(6 and 100 mg/kg)and two egg storage times(0 and 14 d).Based on Exp.1-1,after incubation of eggs collected at week 10(stored 0 d)and week 8(stored 14 d with 22-24 ℃),104 chicks originated from each hatched treatment were selected and divided into 8 replicates with 13 chicks(5 males and 8 females)per replicate.After weighed at 21 day of age,males and females in the same replicate of each treatment were divided and adjusted to 4 male replicates and 4 female replicates in each treatment.All chicks received the same pellet diet with an addition of 100 mg/kg VE for 42 d.Prolonged egg storage time decreased the body weight(BW)of 21-and 42-d-old offspring(P < 0.05),body weight gain(BWG)and feed intake(FI)of offspring from 8 to 21 d,1 to 21 d and 22 to 42 d(P <0.05);decreased the liver T-SOD activity of 21-and 42-d-old male offspring(P < 0.05);increased the feed:gain ratio(F/G)of offspring from 1 to 7 d(P < 0.05);and increased the serum and liver MDA content of 7-d-old female offspring(P < 0.05).Maternal dietary VE(100 vs.6 mg/kg)decreased the F/G of offspring from 1 to 7 d(P < 0.05);increased the serum T-SOD activity of 21-d-old male offspring(P < 0.05).Prolonged egg storage time decreased the BW of 21-d-old offspring and BWG of offspring from 22 to 42 d(P < 0.05),and showed no effect on female offspring(P > 0.05).Increasing maternal dietary VE levels decreased the serum MDA content of 7-d-old female offspring and 42-d-old offspring originated from eggs stored for 14 d(P < 0.05),but not for unstored eggs(P > 0.05).Exp.3-2 was conducted by a 2 × 2 factorial arrangement with two levels of maternal dietary VE levels(6 and 100 mg/kg)and two egg storage times(0 and 14 d).Based on Exp.1-1,after incubation of eggs collected at week 12(stored 0 d)and week 10(stored 14 d with 22-24 ℃ for 1-7 d and 16-18 ℃ for 8-14 d),128 chicks originated from each hatched treatment were selected and divided into 8 replicates with 16 chicks(7 males and 9 females)per replicate.After weighed at 7 day of age,males and females in the same replicate of each treatment were divided and adjusted to 4 male replicates and 4 female replicates in each treatment.All chicks received the same pellet diet with an addition of 100 mg/kg VE for 42 d.Results showed prolonged egg storage time decreased the BW of 7-and 42-d-old offspring(P < 0.05),BWG and FI of offspring from 1 to 7 d(P < 0.05);increased the serum MDA content of 7-d-old female and 21-d-old offspring,and the liver MDA content of 42-d-old offspring(P < 0.05).Increasing maternal dietary VE levels decreased the serum MDA content of 7-d-old male offspring and increased the serum T-SOD activity of 42-d-old offspring(P < 0.05).Increasing maternal dietary VE levels increased the serum T-SOD activity of 7-d-old male offspring originated from eggs stored for 14 d(P < 0.05)and decreased the liver MDA content of 7-d-old female offspring originated from eggs stored for 14 d(P < 0.05),but not for unstored eggs(P > 0.05).Exp.3-3 was conducted by a 2 × 2 factorial arrangement with two levels of maternal dietary VE levels(6 and 100 mg/kg)and two egg storage times(0 and 14 d).Based on Exp.1-1,after incubation of eggs collected at week 14(stored 0 d)and week 12(stored 14 d with 16-18 ℃),160 chicks originated from each hatched treatment were selected and allocated into 4 male replicates and 4 female replicates with 20 chicks per replicate.All chicks received the same pellet diet with an adlidition of 100 mg/kg VE for 42 d.Prolonged egg storage time decreased the BW of 42-d-old offspring(P < 0.05),BWG of offspring from 22 to 42 d and 22 to 42 d,and FI of offspring from 8 to 21 d,22 to 42 d and1 to 42 d(P < 0.05);and increased the serum and liver MDA content of 21-and 42-d-old offspring(P < 0.05).Increasing maternal dietary VE levels decreased the serum MDA content of 7-d-old offspring(P < 0.05).Increasing maternal dietary VE levels decreased the serum MDA content of 21-d-old offspring originated from eggs stored for 14 d(P < 0.05),but not for unstored eggs(P > 0.05).Exp.3-4 was conducted by a 3 × 2 factorial arrangement of treatments with three maternal dietary VE levels(100,200 and 400 mg/kg)and two progeny dietary VE levels(0 and 35 mg/kg).After incubation of unstored eggs collected at week 9 of Exp.1-2,240 chicks originated from each maternal dietary VE treatment were selected and divided into 12 pens with 20 chicks(10 males and 10 females).The 12 pens per maternal treatment were randomly assigned to 1 of 2 progeny dietary VE(0 and 35 mg/kg)treatments for 42 d.Results indicated that there was no influence between maternal and progeny dietary VE levels on the growth performance of offsprings(P > 0.05).Exp.3-5 was conducted based on the incubation of stored eggs(stored 14 d with 16-18 ℃)collected at week 12 of Exp.1-2.At hatch,130 chicks originated from each maternal dietary VE(100,200 or 400 mg/kg)treatments were selected and allocated into 5 replicates with 26 chicks(12 males and 14 females).All chicks in the three treatments were fed the same pellet diets with no addition of VE for 42 d.Increasing maternal dietary VE levels increased the BW of 21-,28-,35-and 42-d-old offspring and BWG of offspring from 15 to 21 d and 1 to 42 d(P < 0.05);increased the serum and liver T-SOD activity and the liver T-AOC of offspring(P < 0.05);and decreased the F/G of offspring from 8 to 14 d and 15 to 21 d(P < 0.05);and the liver MDA content of offspring(P < 0.05).In conclusion,prolonged egg storage time(14 vs.0 d)decreased the growth performance and antioxidant status of offspring,and the adverse effect was greater as the egg storage temperature was higher.As progeny diet was added with 100 mg/kg VE,maternal dietary VE(100 vs.6 mg/kg)supplementation was beneficial to the early development of chicks and could partly relieve the reduction of antioxidant status of offspring induced by long-term egg storage.As no addition of VE was present in progeny diet,increasing maternal dietary VE(100,200 and 400 mg/kg)levels could improve the growth performance and antioxidant status of offspring originated from stored eggs,in this case,the suitable dietary VE level for brolier breeder was at least 200 mg/kg.Conclusion1.Taking laying performance and hatchability as response criteria,broiler breeder dietary supplementation of 6 mg/kg VE recommended by NRC(1994)met the need of broiler breeder hens beyond 70 wk.Increasing dietary VE levels did not affect the laying performance of broiler breeder hens beyond 70 wk,hatchability of eggs and growth performance of offspring,however,enhanced the antioxidant status of breeder hens,eggs and newly hatched chicks.2.Taking breeder antioxidant status and progeny growth performance as response criteria,the dietary VE level for broiler breeder beyond 70 wk could be set at 100 mg/kg.3.Long-term egg storage increased the embryonic mortality,and decreased the hatchability,chick quality and progeny growth performance.Increasing maternal dietary VE levels could alleviate the decreased hatchability induced by egg storage,which was related to the pathways involved in oxidative stress,cell apoptosis,cell proliferation and differentiation,and embryonic development.The oxidative stress-related gene Ogg1,Gst,Sod3,Selenop1,Mt3,Pon2 and Nrf2;and cell apoptosis and proliferation-related gene Col6a、G0s2、Wnt11、Bok、Casp3、Bax、Bcl2 and Hspb8 were the key genes.4.Taking hatchability and progeny growth performance as response criteria,as eggs were stored for 14 days and progeny diet was prepared with no addition of VE,the suitable dietary VE level for broiler breeder was at least 200 mg/kg. |
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