Effects Of Heat Acclimation In The Middle Of Incubation Period On Alleviating Chronic Heat Stress In White Feather Broilers

Purpose:This experiment explores the effect of thermal training in the middle of incubation on the heat resistance of white feather broilers after birth.Materials and methods:(1)Thermal acclimation test of chicken embryos during mid-incubation:300 fertilized eggs were randomly divided into three groups.Group? is the control group,which is routinely incubated(temperature 37.8 ?,humidity56 %).Groups ? and ? were incubated at the temperature of 39.5 ? and humidity65 % for 6 h/d and 12 h/d on the 7th to 16 th days of incubation respectively.They were subjected to high-temperature for for high temperature thermal training treatment,other times were routinely incubated.The development status of chicken embryos was observed,and the hatching rate,Health rate and dead embryo rate were counted.(2)Chronic heat stress test of white feather broilers:After birth,50 chicks were left in each group,with 5 repetitions,each with 10 repetitions.Conducted a chronic heat stress test in summer for 42 days.The temperature and humidity in the house were recorded every day,the health of the chicken is observed,the number ofill chickens was counted,and the feed consumption of each group was counted;the weight of the chickens were weighed and the rectal temperature of the chicken was measured every 7 days;At 42 days,5 chickens from each group were randomly selected and killed.The spleen and bursa were weighed.On the 17 th,27th,and 37 th days,blood was collected on an empty stomach in the morning,and the serum biochemical indicators,heat shock protein,and related hormones were collected;on42 days,each group was randomly selected to measure the meat yield of 5 pigs.Pectoral muscle tests related proteins and genes.Results:(1)The results of the heat acclimation test in the mid-incubation period showed that,compared with the control group(group ?),the hatching rate and the rate of hatching increased in the experimental group,while the rate of dead embryos decreased.(2)The results of the chronic heat stress test showed that the heat stress index of the chicken house during the test was greater than 155,indicating that the chicken suffered chronic heat stress.Compared with the control group(group ?): the rectal temperature of chickens in group ? and group ? decreased,immune organ index increased,morbidity and mortality decreased;body weight increased,the ratio of feed to group ? > group ? > group ?;breast muscle,Leg muscles,chicken wings and full net weight increase,while abdominal fat decreases;muscle brightnessL~* value decreases,muscle redness a~* and muscle yellowness b~* values increase,drip loss rate and shear force decrease,The diameter,number and density of muscle fibers in group ? increased,and the arrangement of muscle fibers was neat than that in the control group;serum corticosterone and triiodothyronine concentrations decrease,serum thyroxine,insulin,heat shock protein 70 and heat shock protein 90 levels increase;valley Alanine aminotransferase,aspartate aminotransferase,alkaline phosphatase and ?-glutamyl transferase decreased,total protein,albumin,globulin and glucose increased,urea and creatinine decreased,creatine kinase and lactate dehydrogenase decreased,triglyceride Decreased esters,low-density lipoprotein and high-density lipoprotein,decreased uric acid;increased mRNA and protein expression of UCP3 and DIO3 in the liver,and m RNA and protein expression of PCNA,PAX7,IGF-1,GH,DIO3,UCP3 in the muscle Higher than the control groupConclusion: The mid-incubation thermal training can improve the hatching ability of white feather broilers and the heat resistance to high temperature in summer after birth.On the 7th to 16 th days of hatching,the thermal training is performed at a temperature of 39.5 ? and a humidity of 65 % for 12 hours every day Chicken embryos are most effective when they are resistant to heat stress at a later stage.