Feed resource selection of Criollo goats is the result of an interaction between plant resources, condensed tannins and Haemonchus contortus infection

Abstract

The tropical deciduous forest (TDF) is an ecosystem with a heterogeneous array of plant species containing different condensed tannin (CT) content. Recent studies explored the effect of polyethylene glycol (PEG) or Haemonchus contortus infection on the intake and feed resource selection of goats. These factors have not been investigated simultaneously. The present study evaluated the role of infection with the abomasal parasitic nematode Haemonchus contortus and the effect of neutralizing CT with PEG on the feed resource selection of Criollo goats in a cafeteria trial. A group of 22 Criollo goats (31.7 ± 4.8 kg) habituated to browse the TDF, were assigned to four groups: two groups were artificially infected with H. contortus (6000 L3per os) and received PEG (50 mg/day) (INF + PEG group) or no PEG (INF group) and the other two groups were kept free of infection with moxidectin (0.4 mg/kg BW sub-cutaneously) and received either PEG (MOX + PEG) or no PEG (MOX). Intake and resource selection of four shrub plant species (Havardia albicans, Gymnopodium floribundum, Leucaena leucocephala and Piscidia piscipula) by goats, and the dynamics of faecal H. contortus egg excretion were determined daily. Intake varied depending on the interaction between plant resource and the infection level (P < 0.001), and between plant resource and whether goats were dosed with PEG (P < 0.001). Excretion of H. contortus eggs was decreased by 69% and 72% for groups with and without PEG administration, respectively. Infected groups had a higher CT intake. The use of PEG reduced intake of L. leucocephala and increased the selection of H. albicans, a high-CT and high crude protein (CP) resource. Animals infected with H. contortus ingested more high-CT resources. Furthermore, CP intake was lower in PEG dosed goats, possibly to reduce the energetic cost associated with urinary nitrogen excretion. Selection of feed resources varied depending on parasite infection, PEG dosage and plant resource. We concluded that biological interactions influencing intake and selection of feed resources in goats are complex, rather than arising from a single factor such as parasite infection or secondary compounds such as CT. These findings support that goats’ resource selection is a complex process aimed at nutritional optimization.