| To identify several genomic regions and functional genes related to variability of stress reactivity,a molecular genetic marker analysis of behavioral and neuroendocrine responses to a "back-test" stress and transport stress was conducted in pigs,respectively.The F2 generation of Pietrain(PIE)×Erhualian(EHL) cross was studied for their "backtest",neuroendocrine reactivity and pork quality to a 2h environment test,as stress reactivity traits.Animals were typed for a total of 22 markers in stress QTL.The effect of SNPs of mu-opioid receptor gene(MOR) on stress reactivity and neuroendocrine responses(including bactest scores,plasma cortisol levels in responses to transport stress) during transport stress in Erhualian Pietrain were analysised.1.Effects of 22 microsatellite DNA markers on "baektest"and transport stress trait in F2 population of pigsWe analyzed the effects of 22 microsatellite DNA makers loci on transport stress including plasma concentration of hormones and pork quality following transport trial and "backrest score" in pigs.These subjects were selected from the segregating F2 generation of a PIE×EHL cross,two swine strains differ in stress tolerance.A so-called Backtest Score(BS) at 3,10 and 17 days after birth(BS3,BS10 and BS17) was implemented to assess the behavior responses for each piglet.Plasma concentrations of Insulin,ACTH,Cortisol,T3 and T4 and pork quality including pH45min,pH24h,tenderness,water holding capacity,cooking loss,and color scores-1*, a*,b*,were measured in pigs after the 2 hours' transport.One-way ANOVA was applied to analyze the relation between microsatellite polymorphisms and behavior responses and transport stress traits.The results revealed that the allelic number was 3～8,heterozygosity was 0.4155～0.7432 and polymorphism information content was 0.3651～0.8150.The effects of SW2446(P＜0.01),SW1816(P＜0.05) and SW0092(P＜0.05) on BS10 were significant,and the effects of SW2108,SW1816 and SW1023 on BS17 were also significant(P＜0.05).SW1808(P＜0.01) and SW0320(P＜0.05) had significant effect on ACTH.The effect of SW1303 on Insulin,SW1092 on Cortisol, SW0320 on T3,S0101 on T4,and SW2446 on BS3 reached a significant level at P＜0.05,respectively.S0101 had significant effect on meat color-a*(P＜0.01).The effect of SW1023 on water holding capacity(WHC) was significant(P＜0.05).The effects of SW1808 on WHC(P＜0.01),meat color-1*(P＜0.05) and b*(P＜0.05) were significant,respectively.Both S0112 and S0092 had significant effects on pH45min (P＜0.05).Our study suggested that these mierosatellites in swine were closely associated with behavior responses and transport stress traits,respectively.2.The A992G mutation of MOR gene is closely linked to reactivity in response to stress in pigsThe effect of A992G mutation of MOR gene on stress reactivity and neuroendocrine responses during transport stress in EHL(n=25) and PIE(n=12) were analysised.It is interesting that all PIE pigs were homozygous for A992A alleles and Halnn,whereas all EHL pigs were homozygotis for G992G alleles and HalNN.To evaluate the stress resisting,piglets were subjected to "Backrest" on 3,10 and 17 days after birth.Blood of the pigs was taken by catheter,at-15,0,15,30,60,120,and 135min,7 different time points during the 2 hours' transport trial,to measure the levels of stress hormones(cortisol).The result revealed that pigs with GG genotype exhibited a declined mRNA expression of MOR gene in pituitary(P＜0.01).The subjects with GG allele had significantly lower Backtest scores(P＜0.01),while higher basal and stimulated plasma cortisol levels in responses to transport stress (P＜0.01 and P＜0.05,respectively).Our results suggest that MOR A992G genotypes in swine can contribute to individual variability in stress response.Considering the effects of stress neuroendocrine systems on energy fluxes and protein deposition,and the importance of stress reactivity for meat quality and animal welfare,these results open new perspectives for pig selection.
|
PDF Full Text Request