Association between over-chlorinated drinking water and adverse reproductive outcomes in gilts and sows: a case report

The present report describes a series of adverse events recorded in gilts and sows at a pig-breeding farm. The animals were listless, had poor appetite and dyspnea, sneezed and coughed, but were afebrile. Subsequently, an increased number of spontaneous abortions occurred, eventually rising to 50 times their average number. The usual infective causes of abortion were ruled out by diagnostic testing; however, the results of drinking water analysis pointed to over-chlorination, with a free chlorine residual concentration of 2.11 mg/l, caused by failure of the chlorinator dispenser connected to the water supplying system seven days previously. Analysis of data on reproductive parameters indicated that the over-chlorinated drinking water directly induced an increase in the number of abortions after only two days of consumption, whereas 7-day consumption of over-chlorinated drinking water had a direct delayed effect on the increased return to oestrus in gilts and sows, and on the increased percentage of stillborn piglets (all P < 0.001). The consequential indirect delayed effect manifested itself as a reduced number of farrowings in gilts and sows, and a lower total number of piglets born (both P < 0.001).