New Study: Intensive Breeding Causes Fatty Stripes in 80 Percent of Chicken Breasts

A new study reveals that more than eight out of 10 packages of chicken breasts sold in major grocery stores contain meat with fatty white stripes. These stripes run parallel to muscle fibers in chicken breasts and, research shows, can lead to a 224 percent increase in fat content, a 9 percent decrease in protein, and reduced levels of amino acids. The fatty white stripes are also evidence of the appalling conditions factory-farmed chickens endure.

Conducted by The Humane League U.K., the study points to the rapid growth of chickens as one of the culprits. Chickens raised for meat—known as broilers—have been bred to grow unnaturally fast. In fact, chickens today grow six times as fast as they did in 1925.

Intensive breeding causes these birds to suffer a wide range of issues, including high rates of lameness and heart disease. This, coupled with the overcrowded sheds they are forced to live in, makes getting enough exercise impossible and leads to fatty deposits in their bodies.

But fatty white striping is only one problem; 4–5 percent of broiler chickens suffer a condition that causes “spaghetti meat,” stringy enough to be pulled apart by hand. And 5–10 percent suffer “woody breast,” a condition that causes hard fibers to develop in the birds’ muscle tissue and meat that is unusually tough.


Earlier this month, Global Animal Partnership published the initial results of the first multidisciplinary chicken-welfare research project to include welfare indicators such as behavior, mobility, anatomy, and physiology. Scientists studied 7,500 chickens from 16 different strains over the course of two years. They found that rapid-growth strains had several significant issues related to poorer welfare, such as reduced mobility, skin lesions, muscle damage, and inadequate heart and lung development.

The results of this groundbreaking study will be used to designate the breeds of chickens that can be used by the nearly 200 food companies that have adopted the Better Chicken Commitment (a set of higher-welfare standards), including Subway, Burger King, Popeyes, and Starbucks. Mercy For Animals president Leah Garcés said in a statement:
Food companies and chicken producers can no longer claim plausible deniability for the many problems related to these fast-growing breeds. It’s time for the poultry industry, grocers, retailers, and restaurant chains to stop sourcing chickens from these terrible breeds and switch to already available breeds with higher animal welfare outcomes.
Help make a difference for animals! Tell meat producers to do better by adopting the Better Chicken Commitment, and download our FREE Vegetarian Starter Guide to start cooking up some satisfying plant-based meals.