The Effect Of Heat Stress On Laying Performance And Tissus Injry In Laying Ducks

The aim of this study was to explore the effect of heat stress on the egg performance and organ injury in laying ducks.80 270-day-old laying ducks were randomly selected and divided into normal group and heat exposure group which ducks were exposured to 35℃for 9 h/d and 24 h/d.The experiment period was 58 days,Before 7 days old,the ducks were lived in normal temperature room,and from 8 to 37 days old they were treated with9 hours of heat stress,and from 38 to 58 days old they were treated with 24 hours heat stress per day.The egg production,water consumption,feed intake,egg quality,follicle development,the level of hormone,mRNA level of gene expression,the content of cytokines and tissue damage were detected.Especially,we focus on the changes of genes Gn IH,HSP90,HSP70 and NLRP3.High temperature of 35℃affected the egg performance by temporarily affecting endocrine and follicular development,promoted drinking and feed intake,had no significant effect on the egg quality in laying ducks;Heat stress of 35 for 24 h/d significantly increased serum FSH,LH,and P₄ concentrations at 21 d（P<0.01）,but had no effect on T₃ and T₄;the expression levels of GnIH,GnRH,VIP,CHR,and PRL mRNA were significantly or extremely significantly increased after 9 h/d of heat stress on d37（P<0.05 and P<0.01）.There was no significant difference at d 58,and the mRNA level of FSH gene was higher in d 37 and d 58 than that in control groupHeat stress can induced some damage in the tissue of liver and intestinal,except spleen.In duodenum and jejunum tissues,the heat stress reduced the length of intestinal villus.However,there was no obvious effect on serum TP,ALB and GLB,but induced the TP decreased.;Heat stress induced the SOD improved at d 37（P<0.05）,decreased the GOT at d37 and AKP at d 8（P<0.05）,but there was no obvious effect on serum TC,TG and GPT.Heat stress significantly increased serum IL-1βat d 37（P<0.05）except IL-18,Heat stress effected the gene expression,such as HSP70,of liver and spleen,IL-6,of spleen,and ASC and IL-18 of duodenum had significant or extremely significant difference（P<0.05 and P<0.01）compared with control group at d 1,IL-8 of spleen increased significantly at d 8and significantly decreased at d 58 but except other indicators among three tissuses.The results show that 35℃affects the egg performance temporarily,liver damaged and,reduced the intestinal villus of duodenum and jejunum.