Evaluation of stress due to mixing in piglets

The aim of the present work was to evaluate the effect of mixing on some physiological indicators of welfare in piglets fed or not with a natural antioxidant supplementation. Fifty six piglets of average live weigh of 6 kg were allotted to two dietary treatments: control diet (CON, N=28) and diet supplemented with dietary plant antioxidant (1 kg/t feed) titrated at 0.5% of phenylpropanoids, expressed as verbascoside (PPG, N=28). After 30 days of dietary treatments, blood samples from 14 piglets/treatment were analysed for serum haptoglobin (Hp), cortisol, blastization of lymphocytes (BLA), aspartate amino transferase and birilubin (BIL) concentrations and blood antiradicalic activity through kit Radicaux libres (KRL) test, “SPIRAL Patent”, Couternon, France. After sampling, inside of the same dietary treatment, the half of animals were mixed with animals coming from another pen. After 2 days corresponding to the period able to develop a dominance hierarchy, blood samples of the new groups of animals were withdrawn for the same blood tests. Data were analysed by a GLM with dietary treatment and mixing as main effects. PPG diet tendentially (P=0.073) increased BLA and reduced (P<0.05) Hp; mixing reduced (P<0.05) BIL and increased BLA (P=0.003). PPG diet (P<0.05) and mixing (P<0.001) increased total antiradicalic activity in blood, expressed as the time (min) required to reach 50% of maximal hemolysis, referred to the whole blood resistance to free-radical attack. The present trial confirms the efficacy of dietary natural antioxidant evidenced by lower haptoglobin values in the PPG group than control; moreover KRL test has been able to discriminate pig welfare in relation to the stressful event such as mixing whereas the physiological parameters frequently used as indicators failed.