The tail biting pig: nutritional and physiological approaches to understanding the behavior
Year: 2016
Type: dissertation
Abstract: Tail biting in pigs is a phenomenon which has been known since the 19th century. The prevalence of tail biting damage is estimated to be between 3 10 % of pigs slaughtered, being somewhat higher in non-docked than tail-docked populations. Being tail bitten causes pain and a state of stress to the victim pigs, as well as general disturbance in pig groups. The aim of this thesis was to improve animal welfare by generating new knowledge for resolving the multifactorial mystery of tail biting behaviour. The precise etiology of tail biting behaviour is unknown, although many risk factors have been identified. The most supported theory of tail biting involves lack of opportunities for pigs to fulfil their innate need for exploration and foraging behaviours in modern production environments. Both these behaviours are mainly performed orally. Deficiencies in the nutritional state of the animal can increase the motivation for foraging behaviour. The three studies presented within this thesis used a case-control design, with questionnaires to investigate feeding and diet related, and environmental risk factors for tail biting damage at a population level, and animal studies to search for differences in intestinal cell wall structure, nutritional state, blood metabolites and different brain area concentrations of serotonin and dopamine and their metabolites between tail-biter pigs, victim pigs, control pigs in tail biting pens and control pigs in non-biting pens at the individual level. Results from the population level study identified environment-, feeding- and management-related risk factors that were similar to those reported in earlier published epidemiological studies of both long-tailed and tail-docked pigs. Interactions between different types of risk factors were depicted. Both the etiologies of tail biting which originates from exploratory and foraging behaviour can be supported by the risk factors found here. The similarities between the risk factors for tail biting and gastric ulceration needs more attention in future studies. Tail biting pigs were found to have elevated serotonin metabolism in the prefrontal cortex (PFC). The serotonin precursor, tryptophan, and its ratio to other amino acids in blood, correlated with serotonin metabolism in the PFC. Experience of stress is suggested to explain the findings in the brain. The influence of enhanced serotonin turn-over on amino acid metabolism needs further study. Tail bitten pigs were found to have decreased concentration of several non-essential amino acids in blood, and a higher ratio of metabolites of serotonin and dopamine in the striatum and in the limbic cortex. These findings are possibly associated with the experience of stress from being bitten, and a change in protein metabolism arising from the acute phase reaction. In a pen where tail biting was present, it was not only the biters and bitten pigs that were affected by this, but also the control pigs. Control pigs were found to have reduced intestinal villus height and changes in blood nutrient concentrations that indicate short term malnutrition, possibly resulting from changes in feed intake.
Source: Työväentutkimus Vuosikirja
Author: Pälvi Palander
Language: English
Subfield: Animal Science and Zoology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2522588081