Causes of pre-slaughter mortality in Danish slaughter pigs with special emphasis on transport

Abstract

AbstractAnnual statistics for transport and lairage mortality were used to investigate factors leading to pre-slaughter mortality in Danish pigs. A subset of material from 2002, amounting to 17.8 million pigs, was used for a more detailed study of the effect of producer, haulier, abattoir and transport distance (< 100, 100–200 and > 200 km) on transport mortality. Total mortality was reduced eight-fold during the period that the halothane gene was being removed from the pig population, from 0.12% in the early 1980s to 0.016% in 2002. Overall, transport mortality increased with higher temperature and lower relative humidity/wind speed but a combination of temperature and humidity that fell into the danger zone, as defined by the Livestock Weather Safety Index, almost doubled transport mortality from a level of about 0.016 to 0.031%. Multiple deaths on the same transport were also more frequent during the hotter months of the year. Transport mortality increased with increasing transport distance, especially during warmer weather. Producers, hauliers and abattoirs had widely varying transport mortality. Eighty-nine percent of producers, 11% of hauliers and 86% of farmer transports had no mortality at all. Producers and farmer transports supplying less than 1,000 pigs had a higher transport mortality than those supplying more pigs, whereas it was independent of supply for hauliers. There were many confounding factors in this work, as producers, hauliers and abattoirs are linked and trends over the years can be affected not only by changes in the genetic makeup of the pig population but also by improvements in handling. Nevertheless, the study shows that internal environment within the vehicle and transport pattern, including the time the vehicle is stationary, are important factors for mortality and that particular efforts should be made if weather forecasts predict dangerous combinations of temperature and humidity. It is suggested that efforts to further reduce transport mortality in Danish pigs should concentrate especially on these factors and include a routine follow-up of all multiple deaths to pinpoint specific factors leading to mortality.