A pilot study on the effect of feed supplementation with magnesium oxide and magnesium aspartate on blood magnesium content and tail lesions in pigs under practical on-farm conditions.

Tail biting in production pigs is a complex behaviour often triggered by stress and nutritional deficiencies, posing significant welfare and economic challenges. Despite the EU ban on routine tail docking for welfare reasons, docking remains effective in preventing tail biting, which highlights the need for alternative strategies and yet better understanding of the complex mechanisms behind it. This study investigates the efficacy of magnesium supplementation, specifically magnesium oxide (MgO) and magnesium aspartate (MgAsp), in reducing tail biting incidents in pigs postweaning until life week 9 (rearing pigs) with intact tails. Conducted on a Danish farm raising pigs with undocked tails, the trial involved 381 pigs across two batches. Blood magnesium and cortisol concentrations, along with tail and ear lesions, were systematically monitored. Results indicate a decline in blood magnesium levels across all groups after three weeks (i.e. life week 7 of the pigs), coinciding with increased incidences of tail lesions, particularly significant in the group with MgO supplementation. However, discrepancies in magnesium concentrations at the initial time point in the group with MgAsp supplementation suggest potential variations in magnesium absorption or baseline levels unknown prior to supplementation. While MgAsp showed some efficacy in maintaining higher magnesium levels, neither form of magnesium consistently reduced lesion prevalence or stress markers, as indicated by cortisol levels. These findings suggest that while magnesium supplementation can influence magnesium status, its role in mitigating tail biting and associated stress may be limited in the age class of rearing pigs. Further research is necessary to explore magnesium metabolism in young pigs and its intricate relationship with stress, nutrition, and behaviour.