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Growing pigs often show aggressive behaviour that can reduce their welfare. Addition of magnesium (Mg) to the diet could reduce these, as Mg supplementation has been associated with improved coping ability in response to stress. This study examined the effect of supplementation with a Mg-rich marine extract - based product (supplemented) on the behaviour, skin and tail lesion scores and salivary cortisol concentrations of growing pigs. A total of 448 pig with 28 days of age were assigned to either Control or Supplement (0.0 5%) diets in single-sex groups. Four weeks later, pigs were blocked according to weight and back test scores. Seven pigs from each pen were mixed with seven from another pen of the same sex and dietary treatment. There were four treatments: control male, supplemented male, control female and supplemented female (n= 4 of each) and the experiment period lasted 9 weeks. Behaviour was recorded in each pen once per week: aggression (fight, head-knock and bite); harmful (tail-in-mouth, ear-chewing and belly-nosing); and sexual/ mounting behaviour. Four focal pigs were selected from each pen, and their behaviour was continuously recorded twice on the same day. Saliva was collected once per week with a cotton bud during 1 min. Salivary cortisol was analysed by an enzyme immunoassay. Skin and tail lesions were scored according to severity once per week.
In Supplement pens were less aggressive behaviours (P<0.01), and mounting behaviour was almost three times lower in supplemented than in control pens (P<0.01). Behaviour on the focal pigs showed no treatment effect on the duration or incidence of aggressive incidents. Supplemented pigs spent less time performing harmful behaviours compared with control pigs (P<0.001) and had lower salivary cortisol concentrations (P<0.01). Supplement females showed lower skin lesion scores, in particular in the ears and shoulders (P<0.01). Mounting is a major welfare concern in uncastrated pigs, and therefore this represents an important welfare benefit of the magnesium supplement. On the other hand, there was no effect on pig performance during the experiment.
Supplementation with a mineral-rich marine product reduced salivary cortisol, aggressive behaviours, sexual behaviour in entire males and skin lesion scores in females, thereby offering improvements to the welfare of growing pigs in an intensive production system. In conclusion, it suggests that addition of a magnesium rich marine extract improved pig welfare in those systems.
K. O’Driscoll, D. M. O’Gorman, S. Taylor and L. A. Boyle (2012). The influence of a magnesium-rich marine extract on behaviour, salivary cortisol levels and skin lesions in growing pigs. Animal, 1-11. doi:10.1017/S1751731112002431
