Avoiding boredom and mitigating stress Poor management practices can generate stress and aggres- sion from early in life. Young piglets that have to compete for food, or are in a poor environment or are subject to excessive handling will suffer setbacks in performance. They will be more prone to aggressive behaviour in later life, such as pro- longed fighting after mixing. Mixing of groups throughout life can be stressful because each mix requires pigs to form a new hierarchy. In gestating sows, for example, providing a calm environment and increasing nutrient concentration with proper body con- dition management will reduce stress and limit aggression. Investigations into pig behaviour have identified that bore- dom carries a high risk score of more than 50%. Where ade- quate materials are provided, at the correct height and in the right place, that enable pigs to chew, move or eat and where competition for these materials is limited, aggression and tail biting is lower than in situations where these enrichment materials are missing or limited.
Nutritional solutions Literature reviews support the links between nutrition and behaviour that have been identified in trials. While nutrition is not a silver bullet for reducing all aggressive behaviour, it has been shown to play an important part in supporting effi- cient and more welfare-friendly pig production across different age groups. A trial at Cargill Innovation Center in the Netherlands com- pared the ratio of two essential amino acids, tryptophan and lysine. Post-weaned piglets were mixed twice, on day 22 and on day 38, to create a social challenge, and body lesion scores were assessed. The batch receiving the higher level of trypto- phan in the ration showed lower body lesion scores. Trypto- phan has a role in the production of the hormone serotonin that is known to lower cortisol levels.
70% 72% 74% 76% 78% 80% 82% 84% 86% 88% 90% 92%
Figure 2 shows that the groups of pigs with the highest level of tryptophan in their diets spent more time lying down and, therefore, less time exhibiting aggressive behaviour. Carefully developed combinations of herbs with specific properties can reduce stress and anxiety and lead to a calmer environment by acting on brain activity, modulating and in- hibiting certain pathways that are linked to the stress re- sponse and secretion of hormones. Other plants have been shown to be beneficial in reducing oxidative stress in pigs. These products, which work in a complementary way, can also have anti-inflammatory properties and various other ef- fects linked to welfare.
The relevance of welfare and sustainability Consumers, producers and pig industry stakeholders have re- alised the relevance of animal welfare and sustainability. With welfare issues in pig production, such as tail biting and ag- gression, being multifactorial, there is no single solution. Scientific and practical evidence should be used by the whole industry to develop a holistic approach that combines management and nutritional solutions.
Level 1 Level 2 Level 3 Level 4 P trt < 0.05 P lin < 0.05 P quad < 0.05
Good example of a high-wel- fare farm: Ges- tating sows in a straw-bedded environment.
D21 p.w. (pre-mixing)
D22 p.w. (post-mixing)
D37 p.w. (pre-mixing)
D38 p.w. (post-mixing) ▶PIG PROGRESS | Volume 36, No. 10, 2020 19
Probability of spending time lying
PHOTO: RONALD HISSINK
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