Water sprinkling market pigs in a stationary trailer. 1. Effects on pig behaviour, gastrointestinal tract temperature and trailer micro-climate

Abstract

Pigs are often transported to slaughter under conditions outside their thermo-neutral zones, which can lead to reduced welfare and increased losses. Water sprinkling in barns is used to control microclimate resulting in pig body temperature reduction and improved welfare; however there is no clear evidence of these effects during transport. The aim of this study was to observe the effect of sprinkling pigs in trailers on behaviour and body temperature during transport and lairage, as well as to observe the effects on trailer microclimate. In each of 12 weeks, 2 pot-belly trailers with 208 pigs each (n=4992) were transported from the same farm on the same day 2h to slaughter. One trailer was equipped with sprinklers that ran for 5min (~125L) before departure and before unloading, the other trailer served as the control. In each trailer, 4 compartments were outfitted with cameras, ammonia detectors and temperature/humidity data loggers. The gastrointestinal tract temperature (GTT; °C) of 4 randomly chosen pigs (n=384) in each test compartment was recorded using orally administered data loggers. Trailer and deck loading order were randomized. Behaviour during transport, unloading and lairage was recorded from video or live observations. Data were analysed through ANOVA with ambient temperature external to the trailer (AmbT) as a covariate. AmbT averaged 19.5°C±3.8°C (range: 13.6–25.8°C). Sprinkled trailers showed lower (P=0.002) increases in internal compartment temperature from loading to unloading, smaller (P<0.001) decreases in humidity and no difference in ammonia levels. At AmbT>23°C, there was no effect of sprinkling on behaviour on the trailer, but at AmbT<23°C, more pigs stood on sprinkled trailers (P<0.05). Sprinkling did not affect slips or falls during unloading. In lairage, latency to rest was reduced as AmbT increased for all compartments (P<0.05); sprinkled pigs spent more time lying (P<0.05) and had fewer drinking bouts than controls (P<0.001) regardless of AmbT. GTT increased between loading and departure and decreased during transit for all pigs (P<0.001); and sprinkling tended to further reduce GTT at arrival at AmbT>24°C (P=0.08). These data suggest that sprinkling pigs in a stationary vehicle when AmbT exceeds 23°C has the potential to prevent increases in body temperature during short duration transport without detrimental effects on ammonia levels or behaviour during unloading.