51 Use of Plant Secondary Metabolites and Impact on Beef Cattle Production

Abstract The objective of the presentation is to describe the beneficial roles of plant secondary metabolites in beef production with special attention to mode of delivery. Plant and fungal secondary metabolites are responsible for many well-known problems in beef cattle production, such as acute or chronic intoxication. Fescue toxicosis is an example of the latter. However, there are also beneficial effects of secondary metabolites. Plant extracts (e.g., essential oils) that are rich in phenolic compounds and other secondary metabolites have been explored as alternatives to veterinary prophylactic antibiotics, growth promoting antibiotics, and enteric methane suppressants. An example of extracted botanicals is beta-acid from the hops plant. Beta-acid could be considered a model rumen-active phytochemical because of a similar mechanism of action to ionophores, which allows direct comparison with well-studied, microbially produced drugs. The route of delivery of extracted phytochemicals can also be similar to that of other commercial products. In contrast, other beneficial plant secondary metabolites can be delivered without extraction. Anthelmintic forages have been extensively studied for use in small ruminants. These forages contain concentrations of plant secondary metabolites, such as condensed tannins or sesquiterpene lactones, that reduce parasite load without processing the plant. Similarly, health and production benefits were shown in cattle consuming isoflavones by grazing forage legumes (red clover) or by supplementation with hay or other minimally processed legumes (red clover, white clover, soybean meal). The term, functional feeds, borrows from the idea of functional foods in human nutrition, this is, foods that have a benefit traditionally ascribed to medicine. Functional feeds may have advantages over commercially extracted and processed phytochemicals, not the least of which is the ability of cattlemen to produce their own feed. However, to fully take advantage of beneficial forage plant secondary metabolites more research is needed in animal nutrition, plant sciences, and chemical analysis.