CAUSES OF MORTALITY AMONG SOWS IN DANISH PIG HERDS

The likely causes of sow mortality in Danish pig herds were investigat ed in a sample of 598 of the breeding animals delivered to a large ren dering plant in the winter seasons of 1992 and 1993. In 263 cases info rmation about the circumstances of the death or euthanasia and the her d characteristics were available, including the size of the herd, its health status, the age at weaning, the method of feeding and the use o f straw for bedding. For these animals the distribution of likely caus es of death or euthanasia was: leg weakness, 28.5 per cent; problems r elated to farrowing and late pregnancy, 20.9 per cent; disorders of th e digestive system, 17.1 per cent; disorders of the urinary system, 13 .1 per cent; physical injuries, 10.7 per cent; and other disorders, 9. 5 per cent. For the other 335 sows the distribution of likely causes o f death was: leg weakness, 16.1 per cent; problems related to farrowin g and late pregnancy, 10.7 per cent; disorders of the digestive system , 21.2 per cent; disorders of the urinary system, 15.2 per cent; other disorders, 15.0 per cent; and unknown causes of death, 21.8 per cent. According to the official statistics from Danish rendering plants, mo re than 60,000 carcases of breeding pigs were processed during 1992, c orresponding to a mortality rate of 5 to 6 per cent in the sow herds. The mortality rate appeared to increase with increasing herd size, and in herds with more than 100 sows the mortality rate was three times t he mortality in herds with fewer than 50 sows. Compared with previous reports, the proportion of disorders involving the gastrointestinal sy stem has increased during the past 20 years. Gastric dilation is parti cularly common, probably as a result of the intensification of pig pro duction and the associated changes in management practises. The use of straw bedding was marginally significant (P=0.06) and associated with a low frequency of gastrointestinal disorders.