Effects of temperament and handling experience on the stress response and meat quality of pigs
This thesis is an investigation of the effects of the temperament and handling experience of pigs on their ease of handling, stress response and meat quality at slaughter. Pigs often experience stress during transport and handling before slaughter, and this raises serious concerns regarding their welfare and can result in meat quality problems. Little is known about how individual factors and handling experience on the farm influence the responses of pigs at slaughter. Three tests were identified for assessing fearfulness in pigs; the human approach test (HAT), novel object test (NOT) and open door test (DDT), and their reliability when performed on pigs in group-housing was assessed: The HAT and ODT showed reasonable repeatability, and had significant between-test agreement. Bold behaviour in the tests (i.e. short latency to contact an unfamiliar human or object, or to exit the pen) was associated with shorter latency to contact and greater activity during a NOT in isolation, and higher heart rate in the HAT in isolation. The DDT was subsequently used in two studies to assess the temperament of commercially-reared pigs. The first study looked at 637 pigs reared on 19 farms, and found that pigs with shy temperaments received more handler interactions in the crowd pen, and produced lighter meat with lower initial pH, than bold or intermediate pigs. The second study examined the interactive effects of temperament and handling experience on two commercial farms. Handling effects were greater on farm 1, where handled pigs classified as bold produced darker loin muscle and reduced drip loss in ham compared to control pigs classified as bold. In conclusion, this research indicates that temperament tests such as the ODT show potential for predicting behavioural and physiological responses in pigs, and as such may be useful in the development of management strategies or genetic selection criteria to improve the welfare of pigs at slaughter and meat quality. The regular handling of pigs during the finishing phase also shows potential for reducing stress at slaughter and improving meat quality, especially in bold animals.