Effects Of Plant Secondary Metabolites (Flavone) On Foraging Behavior Of Sheep

Plant secondary metabolites widely exist in plants. Traditionally, most studies upon the effects of these compounds on animals focused on their adverse effects, but there is relatively few studies on positive selection of them by herbivores. Apocynum venetum is an officinal plant with high content of beneficial flavone, which can regulate some enzyme actives in response to behavior of herbivore.Taking sheeps as research objects, we studied effects of plant secondary metabolites (PSM) upon foraging behavior of sheep by spraying with different concentration plant extracts from leaf of A. venetum with high content of flavone on Leymus chinensis in indoor controlled experiment. This research attempted to examine role of different concentration plant extracts having high content of flavone in sheep foraging from the perspective of potential positive effect of PSM on herbivores. At the same time, we explored the microwave-based method for extraction of flavone from A. venetum.The results of our experiment showed as follows:(1) The extracting technique of flavone by microwave from A. venetum L leaf was studied in the paper. The results showed that microwave power, solid-liquid ratio and microwave time were main factors influencing extraction of flavone. The extracting rate of total flavone was 1.888 (mg/ml) under the optimal conditions: solid-liquid ratio 1∶25, microwave power 240 W, the water content of leaf 80% and microwave time 2 min.(2) Plant extracts with high content of flavone influence intake of L chinensis by sheep significantly, but low content of flavone have potential positive effect; ingestion of low flavone can improve the intake of Phragmitis communis, which was attributed to enhance fibrous feed digestibility. But have no influences on intake mass of Medicago sativa.(3) With the concentration of plant extracts increase, sheep can detect PSMs and modulate it at fine scale in order to keep blood concentration of flavone under saturation; But sheep can also regulate at large scale to satisfy nutrient requirements and balance.(4) The flavone that sheep ingest significantly increased with the increasing concentrations of plant extracts, though sheep applied behavior regulation.(5) The intake of water by sheep should have a rise trend with the increasing concentration of flavone in plant extracts increase.Overall, the effects of PSMs depend to a great extent on the chemistry of the compounds, their concentrations in the diet and the amount consumed by animal. Sheep that ingest appropriate PSMs should improve their performance. The utilizing mechanism about PSMs by herbivores needs a further study. Based on the results, we suggest that proper utilization of plant which contains PSMs can contribute to improving health of herbivore, subsequently improving meat and milk product quality and safety.