Abstract
Peripheral blood mononuclear cells (PBMC) are an interesting sample for searching for biomarkers with proteomic techniques because they are easy to obtain and do not contain highly abundant, potentially masking proteins. Two groups of pigs (n = 56) were subjected to mixing under farm conditions and afterwards subjected to different management treatments: negative handling (NH) and positive handling (PH). Serum and PBMC samples were collected at the beginning of the experiment one week after mixing (t0) and after two months of different handling (t2). Brain areas were collected after slaughter and neurotransmitters quantified by HPLC. Hair cortisol and serum acute phase proteins decreased and serum glutathione peroxidase increased at t2, indicating a lower degree of stress at t2 after adaptation to the farm. Differential gel electrophoresis (DIGE) was applied to study the effects of time and treatment on the PBMC proteome. A total of 54 differentially expressed proteins were identified, which were involved in immune system modulation, cell adhesion and motility, gene expression, splicing and translation, protein degradation and folding, oxidative stress and metabolism. Thirty-seven protein spots were up-regulated at t2 versus t0 whereas 27 were down-regulated. Many of the identified proteins share the characteristic of being potentially up or down-regulated by cortisol, indicating that changes in protein abundance between t0 and t2 are, at least in part, consequence of lower stress upon adaptation to the farm conditions after group mixing. Only slight changes in brain neurotransmitters and PBMC oxidative stress markers were observed. In conclusion, the variation in hair cortisol and serum APPs as well as the careful analysis of the identified proteins indicate that changes in protein composition in PBMC throughout time is mainly due to a decrease in the stress status of the individuals, following accommodation to the farm and the new group.
Highlights
It is well known that pigs are social and under some circumstances hierarchical animals [1], mixing unfamiliar animals on the same pen produce a stressful situation with physiological consequences on the individuals [2,3,4,5,6]
Hair cortisol decreased at t2 vs t0 and there was a tendency for hair and serum cortisol depending on handling
Serum acute phase proteins (haptoglobin, C-reactive protein (CRP) (P < 0.001) and Pig-MAP (P < 0.1)) decreased significantly at t2, whereas the antioxidant enzyme glutathione peroxidase (GPx) increased at t2 (P < 0.001) (Table 1)
Summary
It is well known that pigs are social and under some circumstances hierarchical animals [1], mixing unfamiliar animals on the same pen produce a stressful situation with physiological consequences on the individuals [2,3,4,5,6]. Positive interactions such as pats, slaps or talking to the animals reduce fear and human avoidance [9]. The presence of a familiar human, providing gentle handling, may calm the animals in potentially aversive situations (e.g. isolation, tethering, rectal palpation, insemination) thereby reducing distress and the risk of injury to animals and humans [10]. The effect of human handling after a stressful situation associated to mixing individuals during farm adaptation in pigs is studied
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