Saliva as a biological matrix to assess piglet’s welfare
In pig farming, identifying potential stress at the farm has multiple advantages. It is known that stress, especially long-term chronic stress, will lead to reduced welfare, suppress the immune system, reduce zootechnical performances and disturb breeding performances implying economical losses for the farmer. Therefore, a fast, easy, reliable, and objective tool to monitor stress can provide beneficial information for the farmer and benefit welfare. Already numerous methods to assess a pig’s welfare exist, unfortunately, all with their own limitations. As a result, no definitive set of parameters or indicators of animal welfare exists. Therefore, the goal of this research project was to explore saliva, more specific the salivary proteome, as a tool to identify chronic stress in piglets. Since knowledge of the protein composition of porcine saliva was scarce, the first goal of this thesis was to study and expand the knowledge about the porcine salivary proteome. Because whole saliva, i.e., saliva that is secreted in the oral cavity is mixed with gingival crevicular fluid, buccal cells, microorganisms, and food remnants, gland-specific saliva was collected as ductal secretions. A total of 122 porcine salivary proteins and six mammalian salivary proteins with a predicted porcine homolog were identified in gland-specific saliva. Once more insight into the porcine salivary proteome was gathered, saliva could be exploited as a tool to monitor chronic stress. According to literature, some factors, like deprivation of cage enrichment, frequent mixing of animals and overcrowding could introduce chronic stress in pigs. However, to verify whether these factors could effectively be considered stressors, cortisol was investigated first. Hair from the stressed group contained significantly higher cortisol concentrations, whereas salivary cortisol concentrations did not significantly differ between groups. Once the effectiveness of the stressors was confirmed, the salivary proteome of chronically stressed piglets was compared with that of control piglets. Shotgun analysis identified 392 proteins in saliva of 28-day-old piglets. The relative abundance of 20 proteins was affected by three weeks of exposure to multiple stressors. From these 20 proteins, eight were selected for further validation with targeted parallel reaction monitoring. This validation confirmed that alpha-2-HS-glycoprotein was upregulated in the stressed group, while odorant-binding protein, chitinase, long palate lung and nasal epithelium protein 5, lipocalin-1, and vomeromodulin-like protein were present in lower concentrations in the saliva of the stressed pigs. It can be concluded that besides expanded knowledge on the porcine salivary proteome, differences in the salivary profile of chronically stressed young pigs could by detected. After further validation, the affected proteins could be used as salivary biomarkers to identify stress problems at the farm, elicit transparency regarding animal welfare to the consumer, and facilitate research to optimise rearing conditions.
Antwerp : University of Antwerp, Faculty of Pharmaceutical, Biomedical and Veterinary Sciences, Department of Veterinary Sciences , 2024
194 p.
Supervisor: van Ginneken, Chris [Supervisor]
Supervisor: van Ostade, Xaveer [Supervisor]
Supervisor: Casteleyn, Christophe [Supervisor]
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Creation 29.03.2024
Last edited 19.06.2024
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