Studies On Blood Bioparameters Correlated With TI Duration And Stress Responses To LPS Stimulation In Different TI Phenotype Of Broilers

Tonic immobility(TI)is an innate response of animals related to fear or stress stimulation.Animals can be classified into long TI(LTI)and short TI(STI)phenotypes based on TI test duration,and TI phenotype can be transmitted to the offspring.In the modern intensive farming,chicken is suffered a variety of stressors which not only decrease animals welfare but also reduce growth performance.Serotonin system and hypothalamic-pituitary-adrenal(HPA)axis have been proved to profoundly affect TI response.In the present study,intraperitoneal(i.p)injection of LPS was used to mimic acute stress,the differences of blood indicators,factors in hypothalamus and HPA axis related to stress response and inflammation were detected between short and long TI phenotypes of broilers.In addition,in order to explore endogenous biomarkers related to TI duration several parameters in plasma were detected in LTI and STI broilers,and the correlation between the level of plasma biochemical parameters and TI duration was analyzed in broilers.1 Exploring biomarkers in plasma linked to TI response in broilersIn this study,yellow-feathered broilers were assigned into STI and LTI groups based on TI duration,and then analysis of plasma parameters was conducted to explore blood biomarkers related to TI duration.The results showed that TI duration significantly correlated with total protein(TP)(P = 0.03)and creatine kinase(CK)(P=0.04).LTI phenotype has lower level of plasma TP than STI(P?0.02),while GLU shows a tendency to be higher than STI broilers(P = 0.08).2 Effect of LPS on growth performance and plasma parameters of broilers showing long or short tonic immobilityBased on TI duration,Ross 308 broiler chickens were classified into two groups,short or long tonic immobility(STI or LTI).After 2h of LPS injection,growth performance and plasma parameters were measured and compared between STI and LTI broilers.The results showed that STI phenotype had greater body weight,and the relative weight of liver to BW compared to LTI broilers.Compared to LTI phenotype,STI showed a higher level of plasma glutathione concentration(P = 0.02).Plasma corticorsterone concentration(CORT)was significantly increased after LPS injection(P = 0.00).The total protein level was lower in STI than LTI broilers,and STI broilers showed higher levels of y-glutamyl transpeptidase and nonesterified fatty acid compared to LTI broilers(P = 0.07 and P = 0.09).LPS treatment significantly decreased the level of total protein,serum albumin and globulin(P = 0.00,P = 0.00 and P = 0.00),as well as alkaline phosphatase(P = 0.02).However,LPS injection significantly increased alanine transaminase concentration in plasma(P<0.05).The concentration of glucose(P = 0.00),cholesterol(P = 0.01),triglyceride(P = 0.03),high density lipoprotein cholesterol(P = 0.05)and low density lipoprotein cholesterol(P = 0.01)was also affected by LPS injection.The concentration of nonesterifiedfatty acid in plasma was markedly increased by LPS treatment(P = 0.00).These results indicated that STI broilers show higher antioxidant capacity and growth performance than LTI.LPS injection caused energy mobilization and liver damages to broilers,and also decreased the antioxidant capacity.Moreover,there was no significant difference in response to acute injection of LPS between STI and LTI phenotype broilers.3 Effects of LPS on inflammation and cholesterol metabolism in liver showing long or short tonic immobilityNumber of studies investigated the effects of LPS on inflammation response and cholesterol metabolism in the liver of broiler chickens,however,whether the duration of tonic immobility play a role in this reaction is still unknown.In this study,11??hydroxysteroid dehydrogenase 2(P = 0.02),inducible nitric oxide synthase(P = 0.00),interleukin-1?(P = 0.00),interleukin-8(P?0.00),transforming growth factor ?(P ?0.00)and lysozyme(P?0.00)were changed after LPS injection,however,the difference reaction of TI only appeared in 11?-HSD1(P = 0.00)mRNA expression level.LPS significantly decreased SREBP1(P = 0.00)and ATP-binding cassette sub-family A member 1(P = 0.00)mRNA expression level and increased cholesterol-7-alpha hydroxylase(P = 0.00).There were no interactions between LPS and TI on cholesterol metabolism in liver.4 Effects of LPS on serotonin system,inflammation and HPA axis in hypothalamus of broilers showing long or short tonic immobilityThe serotonergic system and HPA axis have been proved to profoundly influence TI duration in broilers.In this study,the expression of several regulatory and related genes in serotonergic system,HPA axis and immune inflammation were determined to reveal the mechanism behind the different TI phenotype and response to acute stress.Broilers exposed to LPS had a higher FK506 binding protein 5(FKBP5)mRNA expression(P=0.00),and LTI phenotype showed a higher level of corticotropin releasing hormone receptor 1(CRH-R1)protein(P = 0.04).The expression of dopamine 2(DA2)in LTI group significantly higher than in STI(P = 0.02).LPS injection increased TLR4 protein level in hypothalamus(P = 0.00),and interleukin 1(P = 0.00),6(P = 0.00)and 8(P = 0.00)mRNA expression also increased after LPS injection.These results indicate that LPS activated HPA axis via FKBP5 protein.Several cytokines in hypothalamus were significantly increased by LPS injection indicating the inflammatory response in the central system.Moreover,LPS affected serotonin synthesis via regulating several key targets TPH2 synthesis in hypothalamic sites.Different TI phenotypes mainly reflected the differences of expression of DA2 and CRH-R1 in gene or protein level.