Effect of foliages containing condensed tannins and on gastrointestinal parasites

Many different commercial products are available to remove internal parasites from small ruminants in which the drugs are available and produced in several different physical forms, and sold under various brand names. It is increasingly evident that gastrointestinal parasite (GIP) control programs based on dewormers are failing because of increased dewormer resistance; thus, alternative GIP control strategies are necessary. Leaves from multipurpose trees are often rich in N and minerals, and especially important for animal production during critical periods of the year when both the quantity and quality of pasture is limited. However, leaves or foliage of multipurpose tree species often contain high amounts of secondary compounds, especially tannins, which may have a limited impact on increasing the productivity of the animals. Tannins play a significant role in the nutrition of animals, causing either adverse or beneficial effects on nutrient utilization, health and production. The ideal concentration of CT in forage legumes generally ranges from 20-40 g/kg DM, at which level they may bind with the dietary proteins during mastication and protect the protein from microbial attack in the rumen. CT have biological effects on the control of GIP; possible direct effects could be mediated through CT-nematode interactions, which reduce nematode viability. Recent studies in Vietnam have reported that anti-parasitic agents extracted from plant materials for the control of parasites in goats were successful and have been introduced in practice as Citrullus vulgaris for tapeworms, Gliricida sepium and Artocarpus heterophilus for common intestinal worms, and Areca catechu for liver fluke. Alternative forages of Mimosa, Papaya, Leucaena leucocephala, Goava leave Mimisa spp. and Flerningia macrophylla have effects on larvae of Haemonchus in vitro. Research on the effects of Cassava, Jackfruit and Leucaena leaves, Guinea grass and Ruzi grass or cutting height of guinea grass in diets on infection rates of intestinal nematodes and live weight gain of goats has been undetaken. The strongyle egg counts and coccidial oocyt counts were much lower with goats fed foliage of Leucaena, Jackfruit and Cassava in comparison with goats fed Guinea grass and Ruzi grass. This indicates a reduced need for anthelmintic drugs to control GIP in grazing goats fed CT-containing foliage. The results showed that differences in parasite infection between forages were probably due to differences in their CT concentration, although further research into the effect of feeding forage legumes containing CT on parasite infections is required. (c) 2005 Elsevier B.V. All rights reserved.