| Two experiments for this thesis, both single factorial arrangement and in a completelyrandomized experimental design, were conducted to study the effects of acute and chronic heat stresson AA boiler breeder hens. The experiment1was to study the effects of acute heat stress onphysiological-biochemical and molecular indicatros of the birds. The experiment2was to test theeffects of chronic heat stress on physiological-biochemical and molecular indicatros of the birds.Two temprature treatments: thermoneutral contol group (21±0.5℃) and variable temprature groupwere used in experiment1. The effects of temprature on12AA19-week-old broiler breeder hens werecommenced at3days formal test after adapting13weeks. All the birds in single cage were dividedinto2treatments, each treatment represented by6replicates of1bird each. In the first day,4tempraturespots:21±0.5、25±0.5、29±0.5、33±0.5℃were set, and added35±0.5℃temprature spot in the third day.Samples of plasma and tissues(heart, liver and breast muscle) of two groups were separately collected ateach and35±0.5℃temprature spot. Blood samples were used for invistigating routine blood indexes,stress hormones(T3,T4,CORT), oxidant and antioxidant indexes(MDA content, PCC, SOD activity),andtissue samples were applied to invistigate oxidant and antioxidant indexes(MDA content,PCC,SODactivity,mRNA and protein expression of MnSOD and HSP, mRNA expression of HSF. The resultsshowed that short-term high temprature decreased T3concentration whereas increased CORTconcentration,which lead to decline plasma TRI and elevate GLU content.Plasma had decreasing MDAdensity, incresing SOD activity and constant PCC when temprature was beyond33℃.35℃hightemprature also inhibited the production of heart MDA content and liver PCC, promoted breast musclePCC, yet tissue activity of tatal SOD, MnSOD, CuZnSOD were not changed, which indicated that liverand heart have better anti-stress capability than breast muscle. We also observed that kinds of HSPwhich adjust heat stress was diverse in different tissues, for example, heart was mainly HSP90, liverwas HSP70.High temprature up-regulated heart HSP90, liver HSP70, breast HSP70and HSP90mRNAexpression. HSF1, HSF2, HSF3, HSF4of heart and liver trended to rise,whereas breast muscle keptstable.The two temprature treatments:thermoneutral contol group (21±1℃) and heat stress group (32±1℃)were used in experiment2,24at the age of19-week-old AA broiler breeder hens were commenced at8weeks formal test after adapting11weeks, for all the birds, raised2per cage were divided into2treatments,14in contol group with7replicates, others in heat stress group with5replicates. Residualfeedstuff was weighed and birds were feed at time of8:30, eggs were collected and egg productionsituation was recorded at time of14:30. Production performance were analyzed weekly. Plasmasamples were sampled at0,7,14,28,42,56d, samples of tissues(heart, liver and breast muscle) weresampled at56d. The sample analysis was the same with experiment1.The results showed that32℃continuous heat stress of8weeks significantly impacted body temprature and egg laying capacity,accompany with declining egg shell quality and no effects on egg quality and reproductiveperformance. This condition would be more obvious as time goes on.Long-term heat stress inhibited T3 and CORT hormone secretion, which influence fat and saccharide metabolism.Longer heat stress timecaused cell membrane impairment and decreasing amount of TP and ALB. for7days heat stressenhanced the lipid peroxidation but was stable subsequently. The protein oxidation had been decreasedat the7th day, increased at the42th day.32℃continuing high temprature of8weeks, there were noprotein oxidation in heart and liver, but adversely in breast mucle. All tissues were without lipidperoxidation,along with unchanged of total SOD, MnSOD, CuZnSOD activity. In the chronic heatstress condition,the adjustment of heart HSF for heat stress was weak,whereas liver HSF2, HSF3, HSF4and breast muscle HSF2and HSF3mRNA expression had increasing trends.In sum, two different heat stress condition had dissimilar effects on AA broiler breeder hens, ofwhich chronic heat stress was more dagerous. |
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