PSIII-42 Diet selection and trade-offs between condensed tannins and nutrients in parasitized sheep

Abstract

Abstract We determined how parasitized sheep prioritize selection of crude protein, energy and a medicinal plant secondary compound (quebracho tannins-QT). Foraging preferences were tested in 40 lambs before experiencing a parasitic infection (Phase 1), during an infection (Phase 2; 10,000 L3 Haemonchus contortus per lamb) and after chemotherapy (Phase 3). Lambs were assigned to four groups (10 lambs/group) such that animals in Group 1 (Control) could choose between rations of high energy (HE) or high protein (HP) density. The other groups received the same choice, but QT were added (4%) to HE (Group 2), to HP (Group 3) or to both HE and HP (Group 4). Intake and preference indexes were analyzed as a split-plot design with lambs nested within group and day as the repeated measure. All groups increased their preference for HE when parasitized relative to Phase 1 (0.66 and 0.44 ± 0.042, respectively; P < 0.05). As a result, lambs increased their intake of digestible energy during Phase 2 (0.126 ± 0.007 Mcal/kg BW) relative to Phase 1 (0.106 ± 0.007 Mcal/kg BW; P < 0.05). These patterns remained during Phase 3. Only lambs receiving QT in the HE increased their intake of condensed tannins from Phase 1 to Phase 2 (P < 0.05). Fecal egg counts (FEC) and blood parameters revealed a parasitic infection (P < 0.05) in Phase 2 that subsided in Phase 3, although no differences were detected among groups (P > 0.05). The importance of protein nutrition on parasitized animals has been highlighted before, but these results suggest that parasitized lambs prioritized the ingestion of energy-dense over protein-dense foods or medicinal condensed tannins. Nevertheless, intake of tannins increased when these compounds were present in the energy-dense food, suggesting that selection of condensed tannins was influenced by the nutritional composition of the foods during testing.