Cows are herbivores and do not naturally eat chickens. Their entire biological system is engineered for a plant-based diet. This article explores the biological reasons why cattle are strict herbivores and examines the abnormal behavioral exceptions that might lead a cow to ingest non-plant material.
The Natural State: Cows as Obligate Ruminants
The bovine digestive system is specialized to process cellulose, the complex carbohydrate found in plant cell walls. Cattle are classified as ruminants, possessing a unique, four-compartment stomach that enables them to ferment and break down tough fibrous material. This complex stomach includes the rumen, reticulum, omasum, and abomasum. The rumen is the largest compartment, acting as a massive anaerobic fermentation vat.
The rumen hosts a dense population of microbes, including bacteria and protozoa, that produce the enzymes necessary to digest cellulose. These microorganisms break down plant matter into volatile fatty acids (VFAs), which the cow absorbs as its primary energy source. This process is optimized for grass and forage, not the complex proteins and fats found in animal tissue.
The physical anatomy of cattle is unsuited for predation or consuming flesh. They lack the sharp, tearing canine teeth of a carnivore, instead possessing broad, flat molars adapted for grinding plant material. They also lack the instinctive hunting drive and coordination required to catch prey like a chicken.
The abomasum, often called the “true stomach,” functions similarly to a monogastric stomach, using strong acids and digestive enzymes to break down proteins. The proteins it handles are largely microbial proteins—the bodies of the rumen microbes that pass through the digestive tract—not complex animal muscle tissue. The system is structurally and biochemically dedicated to a high-fiber, plant-only diet.
Understanding Pica: When Cows Seek Non-Food Items
The rare instances where a cow might ingest non-food items, such as bones or small carcasses, are classified as pica. Pica is not predatory behavior but a symptom of a severe nutritional imbalance. This abnormal behavior is almost always a desperate attempt by the cow to supplement a mineral deficiency in its regular diet.
The most common cause of pica in grazing cattle is a deficiency in phosphorus, a mineral vital for energy transfer and bone health. Deficiencies in sodium or calcium can also trigger this unusual behavior. When the body signals a severe lack of these minerals, the cow may begin chewing on objects like dirt, stones, wood, plastic, or bones, a behavior known specifically as osteophagia.
If a cow consumes a small dead animal, such as a deceased chicken, it is an opportunistic action driven by the mineral craving, not hunger for meat. The cow is seeking the high concentration of phosphorus and calcium found in the bones and tissues, not the nutritional value of the muscle. Ingestion of this hard, indigestible material can lead to serious health problems, including gut blockages or severe damage to the digestive tract.
Pica is most frequently observed in lactating dairy cows or grazing herds during periods of rapid grass growth, which dilutes the available mineral content in the forage. The presence of this behavior signals a systemic problem in the animal’s feed management or the mineral content of the soil and pasture. Correcting the underlying mineral deficiency through targeted supplementation is the required veterinary intervention.
Historical Context: Animal Proteins in Bovine Feed
Public concern about cattle consuming animal matter is often rooted in a historical public health crisis involving human intervention in the bovine diet. Decades ago, it was common practice to supplement cattle feed with a protein source called Meat and Bone Meal (MBM). This additive was made from rendered animal parts, including the remains of other cattle and sheep.
This practice of feeding animal protein back to herbivores inadvertently created the conditions for the outbreak of Bovine Spongiform Encephalopathy (BSE), commonly known as “Mad Cow Disease.” BSE is a fatal neurological disease caused by infectious proteins called prions, which were transmitted through the contaminated MBM. The use of this rendered product recycled the disease through the cattle population.
Following the discovery of the link between MBM and BSE in the United Kingdom, strict global regulations were implemented to protect herd health. Governments instituted comprehensive feed bans that prohibited the use of mammalian protein in ruminant feed. These bans ensure that cattle maintain a strictly herbivorous diet, eliminating the risk of transmitting prion diseases.