Influence of Diet Sequence on Intake of Foods Containing Ergotamine d Tartrate, Tannins and Saponins by Sheep

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Applied Animal Behaviour Science

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Plant secondary compounds (SCs) play crucial roles in plant survival and defense against herbivores and in appropriate amounts SCs provide health and nutritional benefits to herbivores. The presence of SCs in plants is important, and means need to be found to enhance their benefits while minimizing their negative impacts on herbivores. One approach to this challenge is to offer herbivores mixtures of forages with diverse and complementary SCs such that a combination of SCs becomes less toxic than each of its components in isolation. We determined if a diversity of SCs (tannins, saponins, and alkaloids) offered in different temporal sequences influenced intake of food by sheep. In Experiment 1, three groups of sheep (n = 8/group) received a food containing the alkaloid ergotamine d tartrate (EDT) and the same food containing condensed tannins (TAN) in three different sequences. Group 1 received TAN for 30 min followed by EDT for 1 h (TAN → EDT), Group 2 received EDT for 1 h followed by TAN for 30 min (EDT → TAN), and Group 3 (Control Group) received EDT for 30 min followed by EDT for 1 h (EDT → EDT). Experiment 2 was similar to Experiment 1 except a new group of sheep was used and saponins (SAP) replaced tannins. Sheep had greater intakes of EDT when supplemented with TAN (17 vs. 19 g EDT/kg BW/d for TAN → EDT and EDT → TAN, respectively; P = 0.0002) or SAP (SAP → EDT vs. EDT → SAP – 10 vs. 12 g/kg BW/d; P = 0.0979) than when fed only EDT (9 and 7 g/kg BW/d, respectively), regardless of the sequence in which the foods were presented. Intake of TAN was greater for sheep in TAN → EDT than for sheep in EDT → TAN on 4 or the 7 days of the trial (P = 0.0336). Likewise, intake of SAP was greater for the sequence SAP → EDT than for EDT → SAP (6 vs. 2 g SAP/kg BW/d; P = 0.0162). Regardless of sequence, sheep ate consistently more food with EDT than with either TAN or SAP. Sheep had higher total food intake, and they also ate more EDT, when they were fed TAN as opposed to SAP. Under the conditions of our experiment, sheep ate more food with alkaloids (EDT), and perhaps benefitted more nutritionally, when they had tannins (TAN) rather than saponins (SAP) in their diet.

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