The influence of high- and low-fibre diets on the activity of piperazine against Oesophagostomum spp. in pigs.
An in vivo study evaluated the effect of diet on the efficacy of piperazine against nodular worms of pigs. Twenty pigs, later allocated into five groups, were each infected (and 37 days later re-infected) with 3000 infective larvae of a mixed isolate of Oesophagostomum dentatum and Oesophagostomum quadrispinulatum. Beginning on day 23 post infection (p.i.), pigs in groups 1 and 2 were fed a low-fibre diet consisting of 70% barley flour and 30% protein concentrate, while pigs in groups 3, 4 and 5 were fed a high-fibre diet consisting of 55% barley flour, 21% oat-husk meal and 24% protein concentrate. On day 42 p.i., pigs in groups 1 and 3 were orally dosed with 200 mg piperazine dihydrochloride (Ascarex D, 53%) per kg bodyweight, the recommended dose, while pigs in group 4 were given 100 mg kg-1. Groups 2 and 5 served as non-treated controls for the respective dietary regimens. Eight days after treatment, the pigs were slaughtered and worms recovered from the caecum and large intestine (divided into five sections) and counted. The mean worm count reduction (WCR) in group 1 (full-dose piperazine with low-fibre diet) was 89.8%, while the high-fibre diet in group 3 increased the WCR to 99.4%. In group 4, where the pigs were fed the high-fibre diet and treated with only 100 mg piperazine kg-1, the WCR was 90.9%, identical to the "low fibre" group 1 treated with twice this piperazine dose. There was a zero efficacy recorded against immature worms in all three treated groups. The high-fibre diet improved the efficacy of piperazine against more pathogenic and generally more tolerant O. quadrispinulatum to 99.2% compared with 84.3% at the low-fibre diet.