An Investigation of the Effect of Transport Duration on Weaned Piglet Welfare
This thesis reports the welfare impact of transport duration on weaned piglets as assessed using physiological and behavioural measures, the characterization of the trailer compartment environment during long transport, and the evaluation of the physiological impact of weaning. Through the enrollment of two commercial farm operations, a prospective cohort study was conducted and assessed multiple indicators of piglet welfare following exposure to long (>30h) or short (<3h) transport during Canadian summer months. Representative of the North American swine industry, the two operations differed in their protocols for time between weaning and transport; long transported piglets were weaned days before transport and short transported piglets were weaned on the day of transport. Marked physiological compromise was not evident in piglets following exposure to either transport duration; an association between in-transit mortality and transport duration was not observed. However, long transport was associated with increased weight loss and decreased hydration, while short transport was associated with increased muscle fatigue and elevated stress response. Differences in the motivation between duration groups to feed, drink, and rest after transport were apparent; long duration piglets were more likely to feed and drink on arrival, while short duration piglets were more likely to be observed lying down following transport. These behavioural and postural differences appear to be related to both weaning- and transport-associated practices. Examination of focal trailer compartment environments during long duration transport showed that passive ventilation allows for large fluctuations in compartment temperatures outside the thermoneutral zone for newly weaned piglets, even during summer months. Differences in piglet lying and standing during transport between compartments was observed and may be due to differences in the physical environment and subsequent effects on animal comfort. Finally, evaluation of the relative contribution of weaning to the stress response and injury observed after transport demonstrated that weaning-associated stress and lesions remain detectable for at least 72 hours after weaning. It would be prudent to explore how the amount of time between weaning- and transport-related procedures impact piglet welfare in more detail as time between weaning and transport vary among North American swine operations.