Grass Fed vs. Grain Fed: Which Is Better for Cows?

Animal-product labels at the supermarket can be dizzying. Among them is "grass-fed" beef, which informs us that the cow has eaten mostly or exclusively grass throughout its lifetime—unlike traditional, grain-fed cows, whose meat is usually packaged without a dietary label.

While beef enthusiasts will debate the nutritional value and taste, we are more concerned with what cows naturally prefer to eat and how this sector of animal agriculture affects the environment. Here, we explore grass-fed vs grain-fed cows, the labels commonly seen on beef products, and the impacts cows' diets have on their welfare and the environment.

What Does the "Grass-Fed" Label Mean?

According to the Food and Safety Inspection Services (FSIS), the “100% Grass-Fed” label means the meat comes from cattle that were exclusively fed a forage-based diet. This is opposed to non-grass-fed cows who eat primarily grains and are likely confined in feedlots. The grass-fed label also implies that cows had access to a pasture before being slaughtered.

A grass-fed diet may include annual and perennial grass, legumes, cereal grain crops in vegetative states, hay, silage, and other forms of forage. FSIS notes that cattle may receive mineral and vitamin supplements if needed, but that this information must be documented and approved.

Grass-Finished vs. Grass-Fed

While similar, “Grass Finished” and “Grass Fed” have separate meanings. Cows that are grass-finished eat a grass diet specifically at the end of their life, until they reach a desired weight and are slaughtered. It is likely they have had some grain in their diets earlier in their lives.

On the other hand, cows that are grass-fed should have only eaten forage, from the time they are weaned off of milk until they are finished.

Grass-Fed vs. Other Common Labels

The grass-fed label covers what cattle ate throughout their lives and nothing else. This means, unless otherwise labeled, a beef product may include:

• Added hormones (The cow was given hormones during its lifetime, most likely to aid growth before slaughter. If not, the product should have a “Raised Without Hormones” label.)
• Antibiotics (The cow was administered antibiotics during its lifetime. If not, the product should have a “Raised Without the Use of Antibiotics” label.)

Also, while grass-fed cows can be considered pasture-raised, the opposite is not guaranteed. Pasture-raised cattle may still consume grain during their lives. In this scenario, FSIS will provide a breakdown of the diet (i.e., “Made from cows fed 80% grass and 20% corn.”) on a beef product versus the 100% grass-fed label.

Third-Party Certification

For consumers who want to ensure the humane treatment of cows raised for beef, FSIS labels are insufficient. Some beef products receive third-party certification labels, which mean a non-governmental organization has verified the product based on their own standards after a farm inspection. 

American Grassfed Association (AGA) is a top third-party certifier; its Grassfed Standards state that cattle must be on a 100% grass diet, raised on a pasture, never administered antibiotics or hormones, and raised on an American farm (versus being transported). AGA inspects its cattle farms every 15 months as opposed to FSIS, which does not inspect farms after an application and documentation are submitted.

Grain-Fed Cattle and Feedlots

Despite a growing demand for grass-fed beef, the vast majority of beef cattle in the U.S. (about 95%) are still fed a grain-heavy diet. The grain feed provides cattle with a surplus of energy that translates to increased growth. This helps cows achieve a finishing weight quicker—and earlier on in their lives.

The grain feed typically consists of a combination of corn, soy, and wheat. Cattle are fed on feedlots, also known as animal feeding operations (AFOs) or concentrated animal feeding operations (CAFOs).

Almost 60% of all global agricultural land is used for beef production. While AFOs and CAFOs may require less land than pastures designated for beef cattle, the environmental advantages pretty much end there.

Feedlots are often overcrowded. These close quarters increase the risk of infection spreading among cows—although one plus for farmers is they can monitor their cattle more closely and identify and treat sick cows. Feedlots are also manure-heavy and release nitrogen and ammonia both into the atmosphere and into runoff water, contributing massively to air and water pollution. CAFOs, in particular, may produce 117,000 tons of manure per 10,000 cows in just a year.

What Are Cows Supposed to Eat?

Cattle have ruminant digestive systems made up of four compartments: the rumen, reticulum, omasum, and abomasum. When cows eat, the feed gets stored and fermented in the rumen. Microorganisms support the fermentation process by breaking down feed so digestion can proceed. Because of the large rumen and microbial fermentation, cows are biologically able to consume and digest large amounts of fibrous grass.

While they can still consume grain as well, cows that overeat grain—which is lower in fiber than their digestive systems are accustomed to—can develop digestive issues such as rumen acidosis, a disease of excess acid that drops stomach pH and impacts microbial functions. Other problems that can arise when cattle are on low-fiber, high-carbohydrate diets include stress, ulcers, and overgrowth of dangerous bacteria.

Cattle Diets and Carbon Emissions

Cows’ digestive systems favor forage over grain. In addition, grass-fed beef is marketed as better for the environment. But is this true in terms of carbon emissions?

According to the Food Climate Research Network’s report on ruminants, grazing systems, and greenhouse gas emissions, many positive grass-fed claims are either false or exaggerated. The authors of this report looked into whether grazing systems (versus intensive confined systems, or feedlots) can aid in carbon sequestration. They concluded that while there is potential for benefits, particularly where land has been previously degraded and is in need of improvements, sequestration is not possible everywhere, and effects are minimal. 

Likewise, the report highlights that all livestock systems rely on fossil fuels, whether a farm depends on mostly grass or grain for feeding. Therefore, the suggestion of expanding grazing systems to produce more grass-fed beef would not be beneficial—in fact, the added land use would leave us worse off, leading to an even greater release of carbon dioxide. 

Both grass-fed and grain-fed cattle are significant contributors to greenhouse gas emissions and, thus, climate change. With about 41% of all U.S. land going toward feeding animals—this includes both pastures and feedlots—a more important focus than cow's diets is how can we drive down the demand for beef altogether in order to lower agricultural carbon emissions.