Effect Of Early Socialization On Social Behavior,brain Development And Emotional State In Nursing Piglets

Early socialization of piglets refers to the process of starting contact with different litter piglets before weaning.A good livestock house environment not only improves the welfare of pigs from a comfortable environment,but also keeps domestic pigs healthy and emotionally stable during feeding.However,the effect of early socialization on emotional status and brain neurodevelopment in piglets has not been reported.This study explored the effects of different early socialization patterns on the piglets: social frequency and inquiry motivation,brain neurodevelopment and negative emotional resistance through two different(continuous and intermittent socialization).The total of 24 litter(10 / litter,n=240)piglets were equally divided into three groups: control,intermittent and persistent groups.The piglets in the control group did not contact non-littermates during lactation;the piglets in the intermittent group were 1:00 P.M.--4:00P.M.at D14,D15,D21,D22,D27,D28,D33 and D34,Discontinuous social contact;piglets in the continuing group made continuous social contact from D14 until the end of D35 weaning.During the socialization period,adjacent piglets can enter and exit the public communication areas at any time.The results showed that the social frequency among piglets continued to decline throughout lactation,with socialized piglets interacting more actively with peers than controls and intermittently preferring to contact different litter piglets(P<0.05)and persistent socialized piglets(P<0.05);mother and son rising first and then decreasing throughout lactation(P<0.05),and peaked at D28(P<0.05),resulting from increased social frequency.Compared with control piglets,socialized piglets are more motivated to explore,and the improvement of continuous socialization on inquiry motivation is greater than the effect brought by intermittent socialization.From synaptic plasticity and neurotrophic factors in the brain limbic system of intermittent socialized piglets than in unsocialized and sustained socialization,it can be speculated that intermittent socialization patterns alter brain neurodevelopment in piglets.Early socialization begins to affect the emotional state of piglets in the third week of lactation and continues until the end of lactation,with a peak of mood-like neurotransmitters after weaning of mixed groups(P<0.05).The differences caused by early socialization require long socialization processes to emerge without immediate results.The proportion of active emotional state time occupied by intermittent socialized piglets increased(P<0.05),and the proportion of negative emotional state time occupied decreased,mainly concentrated in the third and fourth weeks of lactation(P<0.05).The fourth week of lactation was less resistant to fear,but the difference had disappeared by the fifth week of lactation.Social piglets are less anxious in unfamiliar environments than in the control group,and intermittent socialization is more influential than in the continuous socialization mode.This study concluded: 1)early socialization as a social environment improves the inquiry motivation and social frequency of piglets;2)early socialization environment is conducive to the development of piglets brain edge system(including hippocampus,medial frontal cortex and amygdala);3)piglets experienced early socialization anxiety is better than piglets without social experience,increasing the proportion of piglets expressing positive emotions in feeding.