Effect of dietary tannin and protein concentration on nematode infection (Trichostrongylus colubriformis) in lambs

The aim of this study was to determine whether the inclusion of a condensed tannin (quebracho tannin, QT) and/or the elevation of dietary protein coul d reduce Trichostrongylus colubriformis establishment and existence in the small intestine of lambs. Thirty-six lambs (mean liveweight 32.6 +/- 3.9 kg ) were randomly allocated to one of six experimental groups, groups 1-5 wer e parasitized with a trickle infection of 3000 infective Trichostrongylus c olubriformis larvae daily, whilst group 6 remained as uninfected controls. Experimental diets were formulated to contain 222 g CP/kg (high protein) or 97 g CP/kg (low protein) with or without the inclusion of 50 g QT/kg. All six animal groups were fed the low protein diet, group 2 fed low protein di et+QT, for one month prior to infection (groups 1-5). Once nematode eggs we re observed in the faeces, diets were abruptly changed in three experimenta l groups. Group 1 remained on the low protein diet, group 2 remained on the low protein+QT diet, group 3 changed to the high protein diet, group 4 cha nged to the high protein + QT diet, group 5 changed to the low protein + QT diet and group 6 remained uninfected and fed the low protein diet. Product ion, haematological and parasitological parameters were monitored at regula r intervals. Results show that parasitized animals fed the high protein die t achieved growth rates similar to those of uninfected low protein-fed lamb s. Inclusion of dietary QT did not depress liveweight gain. Total daily fae cal egg counts declined after feeding the high protein diet. Inclusion of Q T into the low protein diet also reduced faecal egg counts to similar level s observed in the high protein-fed lambs. The inclusion of QT into the high protein diet did not further reduce faecal egg counts. No significant diff erences in the haematological parameters measured were observed between inf ected animals (groups 1-5), suggesting that the beneficial effect of dietar y QT in the low protein diet is unlikely to be mediated through an immune r esponse. These data suggest that the inclusion of QT in low protein diets m ay be an alternative to feeding high protein diets to reduce nematode burde n in lambs.