Gastrointestinal nematode infection does not affect selection of tropical foliage by goats in a cafeteria trial.

Abstract

It is important to determine whether gastrointestinal nematodes (GINs) affect foliage choice of goats leading to confirm the expression of a self-medication behavior. This study investigated the effect of GIN infection on tropical foliage selection by goats. During experimental stage 1 (10days), goats had a natural mixed GIN infection, and at stage 2 (10days), goats were treated with effective anthelmintics to maintain them free of GIN infection. During stage 1 the twelve adult goats (32 ± 2.3kg live weight [LW]) were assigned to three groups (n = 4) according to their initial GIN infection status: HI group, with fecal egg count (FEC) between 1450 and 2150 eggs per g/feces (EPG); MI group, medium FEC (592-1167 EPG); and the NI group, free from GIN infection. Fresh foliage of four tropical plants were offered to goats ad libitum for 1h daily: Gymnopodium floribundum (high condensed tannin [CT] content, 37-40%), Mimosa bahamensis (medium CT content, 16-17%), Leucaena leucocephala (low CT content, 3-5%), and Viguiera dentata (negligible CT content, 0.6-0.9%). Jacobs' selection indexes (JSIs) were estimated for the experimental foliage based on dry matter (DM), CT, or crude protein (CP) intake. During both study stages, individual fecal egg counts were estimated. The JSI patterns of different plant species, based on DM, CT, or CP, were similar irrespective of infection level during stage 1 (HI, MI, and NI) or no GIN infection (stage 2). Thus, irrespective of GIN infection, goats actively selected M. bahamensis (high CT, low CP content) and V. dentata (negligible CT, high CP content) but avoided G. floribundum (high CT, low CP content) and L. leucocephala (medium CT and high CP content). Thus, natural GIN infection did not influence goats' foliage selection.