Effect of strategic deworming on Ascaris suum exposure and technical performance parameters in fattening pigs.

The aim of this study was to investigate the effect of a strategic deworming program on Ascaris suum infection levels and technical performance parameters in fattening pigs. Eighteen fattening stables were selected and divided into two groups. Group 1 consisted of 9 stables in which the fattening pigs tested seropositive for Ascaris, indicative for the presence of Ascaris eggs in the stable, whereas group 2 consisted of 9 stables in which the fattening pigs tested seronegative for Ascaris, indicating of a low or absent environmental contamination with Ascaris eggs. The production in each stable was monitored for a period of 7 consecutive fattening rounds. The first of these 7 fattening rounds (i.e. round 0), during which no intervention took place in the deworming strategy applied in the stable, served as a historical control. A deworming program using 200 mg/ml fenbendazole oral suspension in drinking water for 2 days every 6 weeks was implemented for a period of 6 consecutive fattening rounds. For each fattening round and for each stable, technical performance parameters including average daily growth, feed conversion ratio, days in fattening and the percentage of affected livers were obtained from the producers. Blood was collected from 10 randomly selected animals per stable at the end of each fattening round and evaluated for the presence of anti-Ascaris antibodies using 2 different serological tests, namely the AsHb- and the L3-Lung ELISA. The serological results obtained indicated a lower exposure of the animals to Ascaris after the implementation of a strategic deworming program. A significant decline in anti-Ascaris antibody levels was detectable in the stables that originally tested positive for Ascaris and was already visible after one treatment round. The outcomes of hierarchical linear mixed models indicated that the level of L3-Lung antibody reactivity was a significant predictor of decreased ADG, increased FCR and prolonged DIF for the Ascaris-positive herds, indicating an effect of Ascaris infections on productivity.