Plant chemistry (Phytochemistry)

Plant chemistry is included within the domain of plant physiology. To function and survive, plants produce a wide array of chemical compounds not found in other organisms. Photosynthesis requires a large array of pigments, enzymes, and other compounds to function. Because they cannot move, plants must also defend themselves chemically from herbivores, pathogens and competition from other plants. They do this by producing toxins and foul-tasting or smelling chemicals. Other compounds defend plants against disease, permit survival during drought, and prepare plants for dormancy, while other compounds are used to attract pollinators or herbivores to spread ripe seeds.


Antiquality factors affecting animal health

One main trait of top-quality forage is One main trait of top-quality forage is the absence of foreign materials. Nails, wire, and weeds may be harvested with forage or consumed by grazing livestock even though animals have unique methods for selecting the best forage than machinery. But plants can also have traits that reduce the chance of being eaten by livestock. Traits that make plants undesirable for consumption are called antiquality characteristics. Antiquality characteristics can be physical like thorns or chemical like unpleasant odors or tastes. Antiquality characteristics include things that contribute to illnesses, poor animal gains, low consumption, and reproductive difficulties. It should be noted that all forage will most likely contain some unpleasant features and still be consumed by animals if kept in limited concentrations. Lignin, the fibrous portion of stems and stalks, is considered an antiquality factor because it limits digestion rates. So forage harvested at late maturity will contain a lot of lignin and be less desirable to livestock. Sometimes a feature unwanted by livestock may be beneficial in some way to the plant. The endophytic fungus in tall fescue makes the plant stronger leading to stand longevity but is harmful to livestock.

Animals will often not select plants with physical antiquality factors such as thorns, molds, dust, or weeds if there is another choice available. These unpalatable traits reduce intake and some may decrease microbial activitiy in the rumen, reducing digestibility. More often the antiquality factors are chemically based and result in undesirable tastes and odors which influence selection and palatability by the animal. Some chemical antiquality factors cannot be detected by taste or smell and are toxic leading to health problems.

Common antiquality components include:

Lignin: reduces digestibility; late maturity forage has more lignin, less palatable

Tannins: reduce palatability

Saponins: can cause bloat

Coumarin (sweet clover): anticoagulant

Flavonoids: can lead to reproductive failures

Nitrates: nitrate poisoning

Endophytes (perennial ryegrass and tall fescue): toxic ergoalkaloids (Lolitrim b and ergovaline)

Alkaloids: reduce palatability