Sow mortality associated with high ambient temperatures.

A nnual death rate in sows varies considerably among herds but usually ranges from 3% to 8% (1). Based on data from 10 studies on sow mortality, it was determined that torsions and other accidents involving abdominal organs, cardiac failure, and cystitis-pyelonephritis were major causes of sow losses in breeding herds (1). A higher incidence of mortality during summer months was recently reported in commercial breeding herds in which sows were kept in total confinement yearlong (2). Many of the deaths occurring during these warm months were attributed to cardiac failure (2). High ambient temperature, parturition, obesity, and stressful events, such as; mating, fighting, and transport, have previously been identified as predisposing factors for cardiac failure in sows (3). During June 1994, a high death rate corresponding to a period of high ambient temperatures occurred in many herds in our area. The purpose of this investigation was to document the potential impact of high ambient temperatures on the annual death rate in herds of breeding sows raised in total confinement and to suggest some preventive measures. Maximum and minimum outside daily temperatures were obtained from the local meteorological station of the provincial Ministry of Environment for June and July 1994. A period of 7 consecutive days for which the average maximum daily temperature was the highest for these 2 mo was selected. Data from 130 swine breeding herds located in the St-Hyacinthe area were used. All of these herds were housed in total confinement and had computerized sow records. The information gathered from each farm included the number of dead sows and the average inventory for each selected day and for the preceding year. The death rate for a specified period was reported on an annual basis and defined as: