Researchers suggest that livestock benefit from plant diversity
As higher costs and environmental concerns about fossil fuels push more people to buy locally produced food, demand for livestock raised on pastures and rangelands--rather than in feed lots--is spurring a return to greater reliance on native rangelands and cultivated pastures.
These changes will have enormous financial implications for beef producers, according to the authors of an article in the current issue of Rangelands, published by the Society for Range Management. Although there are roughly 200,000 species of plants on earth, only about a dozen account for the vast majority of food production, particularly in developed countries.
"By focusing on a few species, people transformed the diverse world of plants into a manageable domain that generally meets energy and protein needs and limits intake of toxins," writes Frederick D. Provenza and his coauthors in the article, "Value of Plant Diversity for Diet Mixing and Sequencing in Herbivores."
But this practice limits genetic plant diversity and health benefits to livestock from combinations of available plants nutrients, while threatening ecosystems reliant on biodiversity to avoid catastrophe. The researchers suggest a new alternative for livestock grazing that calls for having animals eat a variety of complementary plants. These varied plants would provide a range of primary and secondary nutritional compounds, they write, along with greater health and nutritional benefits--and promote biological diversity.
For instance, tannins are secondary compounds in plants that help herbivores reduce internal parasites and bloat, and they enhance nutrition by providing high-quality protein to the small intestine. Tannins also naturally reduce methane emissions--one way cattle are said to contribute to global warming--and improve the color, quality and flavor of meat and milk for human consumption.
The study also examined how diet sequencing and diet breadth affect animal health. The authors found that some plant combinations can help animals regulate their food intake and fight toxicity, such as that found in a type of fescue grass grown on 14 million hectares of U.S. pastureland. The fescue contains alkaloids that cause severe cattle losses, costing cattle ranchers $500 million annually.
But the research shows that when cattle eat tannin- and saponin-containing plants, the secondary compounds may offset the negative effects of the alkaloids in fescue. "Other toxic plant problems worldwide may benefit from similar research and applications," according to the authors.
The researchers say secondary compounds play an important role in the health of animals, plants, soil and people, but little is known about them because labs currently cannot conduct routine analysis of secondary compounds. The authors call for creation of a database to record the interactions between secondary and primary compounds, document potential toxicity, and to help instigate research into how these compounds may benefit health and nutrition.
The article, "Value of Plant Diversity for Diet Mixing and Sequencing in Herbivores," is part of a special issue on poisonous plants of the United States that is available in its entirety, by visiting: www.allenpress.com/pdf/rala31.1i1551-501X-31-1-45.pdf.