Cows are ruminant animals, primarily grazing grasses and hay. Their digestive system is well-suited to efficiently break down fibrous plant matter. However, these grass-eaters sometimes consume woody plants like trees.
Cows and Woody Plants: An Overview
While primarily grazers, cows may eat parts of trees and shrubs, including leaves, twigs, and bark, especially when preferred forage is scarce. This behavior, sometimes called pica, can stem from a lack of sufficient pasture, curiosity, or a search for nutrients like phosphorus, fiber, or protein deficient in their regular diet.
Unlike true browsers such as goats or deer, cows’ digestive systems are optimized for grass. Goats are highly effective at browsing and controlling brush. While cows can browse, extensive consumption of woody plants is not ideal for their health or the trees.
Potential Risks and Health Considerations
Woody plant consumption poses risks to both cows and vegetation. Woody plants generally offer lower nutritional value than grasses, potentially leading to deficiencies, poor body condition, and reduced productivity if they become a significant part of the diet.
Many tree species are toxic to cattle, causing health issues. Oak trees, for example, particularly their young leaves and green acorns, contain tannins that damage kidneys and liver. Wild cherry and red maple leaves, especially when wilted, are highly poisonous; cherry leaves cause rapid death due to cyanide. Pine needles, when consumed in large quantities, have been linked to abortions in pregnant cows. Symptoms of toxicity often include digestive upset like diarrhea, colic, and abdominal pain, and neurological signs such as staggering and muscle weakness.
Beyond health concerns for cows, their browsing habits can damage trees. Cows may strip bark, a process known as girdling, which can kill a tree by disrupting its nutrient transport. They can also heavily browse young saplings, hindering forest regeneration. Additionally, cattle may rub against trees, especially evergreens, causing physical damage to bark and branches.
Managing Cow Grazing Around Trees
To prevent cows from eating trees and mitigate risks, several management strategies can be implemented. Providing adequate, high-quality forage in pastures is primary, as cows are less likely to browse trees if their nutritional needs are met through grass. This also helps address potential nutrient imbalances, such as low phosphorus, which can drive browsing.
Physical barriers effectively protect trees. Fencing, whether electric or sturdy, can exclude cows from wooded areas or individual trees. Tree protector bags or cages around young saplings also defend against browsing and rubbing. Removing known toxic tree species from pastures reduces poisoning risk. Providing alternative shade structures in open pastures can also reduce the incentive for cows to seek shelter and damage trees.