Pigs in intensive production systems typically experience multiple acute stressors which can have a negative impact on their welfare. This study investigated whether a magnesium (Mg) rich marine extract (SUPPLEMENT) could reduce the negative effects of mixing and an out-of-feed event on pig welfare. At weaning (28. d) 448 piglets were assigned to either control or SUPPLEMENT (0.5% of the diet) diets in single sex groups of 14. Four weeks later (day 56, c. 17. kg) pigs were blocked according to weight and back-test scores. Seven piglets from each pen were mixed with 7 from another of the same sex and dietary treatment to yield the following groups: control male, SUPPLEMENT male, control female and SUPPLEMENT female (n= 4 of each). At mixing, behaviour was recorded on video for 3. h and the frequency and duration of aggressive behaviours, as well as the number of pigs involved in each bout of aggression was recorded. Additionally, the proportion of pigs standing or lying was recorded at 10. min intervals. At 112. d feed was removed for 21. h. After re-introduction of the feed, pens were observed continuously for 8 × 2. min periods and aggressive behaviour was recorded. Skin lesions of 4 focal pigs/pen were scored on the day before and after mixing and the out-of-feed event. Saliva samples were collected on day 56 and day 113 (1. h before and 1, 3 and 8. h after mixing/feed delivery post deprivation) and at 10:00. h on day 55, day 57, day 58, day 112 and day 114 by allowing the 4 focal pigs to chew on a cotton bud for 1. min. Cortisol was analysed by ELISA. At mixing, aggressive interactions between males lasted longer than between females (34:27 vs. 16:55. mm:ss, s.e. 03:38; P< 0.01) and more control than SUPPLEMENT pigs were involved in each bout of aggression (2.13 ± 0.39 vs. 2.08 ± 0.34; P< 0.05). There were no treatment effects on the frequency of aggressive behaviours (P> 0.05). There was no effect of diet or sex on skin lesion scores, but SUPPLEMENT females had lower cortisol concentrations than control females (1.51 ± 0.12 vs. 1.91 ± 0.13. ng/ml; P< 0.05). During the out-of-feed event, neither sex nor diet affected salivary cortisol levels, but males were more aggressive than females (0.182 vs. 0.122 aggressive interactions/pig/min; s.e. 0.019; P< 0.05), and control pigs had higher skin lesion scores than SUPPLEMENT pigs (13.2 ± 1.1 vs. 10.0 ± 1.0; P< 0.05). These findings suggest that the Mg supplement used in this study had some beneficial effects on pig welfare. © 2013.
- Acute stress