Factors Affecting Transport Stress Investigated

US - Temperatures over 17°C and pot-bellied trailers were associated with more stress and longer unloading times in finished pigs, according to new research from Pennsylvania State University.
calendar icon 24 May 2010
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K.B. Kephart and colleagues in the Department of Dairy and Animal Science at Pennsylvania State University have published a paper in the Journal of Animal Science describing their observations of market pigs following transport to a processing plant.

They conducted a field study to record observations of 41,744 market-weight pigs upon arrival at a commercial abattoir to evaluate the relationships between various independent factors and open-mouth breathing, skin discolouration, lameness, unloading time and mortality during transport. Observations were recorded from 242 trailer loads on 46 separate days over a period of 14 months.

They found that travelling time (2.5 hours or longer), waiting time before unloading (20 minutes or longer), loading pressure (260 kg of bodyweight per square metre of trailer floor space or more), ambient temperature while unloading (17°C or above) and trailer type [potbelly (PB) versus straight-deck with conventional unloading doors (SDC) or straight-deck with wide unloading doors (SDW)] were recorded for each load.

Open-mouth breathing was more prevalent in pigs when transported on PB trailers compared with that of SDC or SDW trailers (P<0.01), and at warmer temperatures (>17°C;, P<0.001).

Skin discoloration was more prevalent (P<0.001) in pigs unloaded at temperatures over 17°C. Lameness was more prevalent (P<0.05) after shorter travel times at greater loading pressure compared with shorter travel times at decreased loading pressure.

Unloading time for PB trailers was longer (P<0.001) than for SDC and SDW.

Mortality rates during transport were minimal (0.06 per cent) in the deliveries that the researchers observed, and there were no significant (P>0.10) relationships between mortality and any independent variable tested.

Wait time before unloading was not associated (P>0.10) with any of the dependent variables included in the statistical model.

Kephart and colleagues concluded that warmer ambient temperatures (17°C) and the use of PB trailers are associated with an increased incidence of open-mouth breathing and skin discoloration, and longer unloading times after the transport of market pigs.


Kephart K.B., M.T. Harper and C.R. Raines. 2010. Observations of market pigs following transport to a packing plant. J. Anim Sci. 2010. 88:2199-2203. doi:10.2527/jas.2009-2440.

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