Sequence of food presentation influences intake of foods containing tannins and terpenes

Interactions among nutrients and secondary compounds in plants can influence the kinds and amounts of different forages herbivores ingest, but little is known about how the sequence of plant ingestion may influence these interactions. The physiological pathways and rates of nutrient and secondary compound metabolism in the body influence food intake by herbivores. On this basis, we predicted the sequence in which foods that vary in nutrients and secondary compounds are ingested would influence food intake and preference. In a 2 × 2 factorial experiment, we evaluated the relationship between the sequence of presenting two foods, one with terpenes and the other with tannins, and the time when lambs ate a nutritious food (alfalfa–barley), either before or after eating foods with tannins and terpenes. When alfalfa–barley was fed prior to the terpenes, intake of the terpene-containing food was lower than when alfalfa–barley was fed after terpenes (P < 0.05). The sequence when alfalfa–barley was fed did not influence intake of the tannin-containing food (P > 0.10). Lambs ate more total foods with terpenes + tannins when fed tannins → terpenes → alfalfa/barley than when fed alfalfa/barley → tannins → terpenes (P < 0.10). During preference tests, when lambs were offered all three foods simultaneously, lambs previously conditioned with the sequence tannins → terpenes → alfalfa–barley preferred alfalfa–barley > terpenes > tannins (P < 0.05), whereas lambs in other treatments preferred alfalfa–barley > tannins > terpenes (P < 0.05). During preference tests when lambs were fed only foods with secondary compounds, lambs previously conditioned with the sequence tannins → terpenes → alfalfa–barley showed equal preference for foods with tannins and terpenes, whereas lambs in other treatments preferred food with tannins > terpenes (P < 0.05–0.10). All of these results are consistent with the hypothesis that the sequence in which foods are consumed affects both food intake and preference. Understanding the importance of sequencing when herbivores consume foods that vary in nutrients and secondary compounds may help managers create new grazing strategies that include sequential foraging patterns to optimize food intake and more evenly use all plant species in a community, a practice used by herders in France.