From Wild Jungle Fowl To Monstrous Broiler Chickens

As studies are increasingly revealing an ongoing decline in wild animal populations, human and farmed animal populations keep on rising. In fact, the combined biomass of humans and their domesticated animals now outweighs that of all wild terrestrial vertebrates. Chickens, particularly, are the world’s most numerous birds at 22.7 billion, a population growing exponentially since their estimated domestication about 8000 years ago.

Chicken meat consumption is growing faster than any other type of meat and will soon overtake pig meat, mainly due to expanding consumption in developing countries. Efficient and high-volume production is on the agenda – in the U.S., the top broiler chicken production firm, Tyson Foods, slaughtered an astonishing 35 million chickens in an average week in 2012.

In this study, a group of scientists from the U.K. and South Africa analyzed chicken remains from several different epochs to show that the domestic broiler chicken is a novel morphotype, representing the unprecedented human reconfiguration of the Earth’s biosphere.

The Life Of A Modern Chicken

Domesticated chickens have experienced a steady increase in growth rate since 1964; modern broilers’ growth rate is three times faster than that of the original red jungle fowl. However, recent data show that growth rates are slowing and may actually be reaching a plateau.

The widespread breeding of broiler chickens has resulted in over 65.8 billion carcasses consumed globally in 2016. How is it possible to kill over 65 billion birds if their global population is under 23 billion? It largely has to do with their short lifespans: on farms, chickens are allowed to live just 5-7 weeks. Egg-laying hens are allowed to live slightly longer – roughly a year. Both broiler and egg-laying chickens are eventually slaughtered at such a young age for economic reasons, and this contrasts heavily with the lifespan of the ancestral red jungle fowl (3-11 years in captivity) and companion chickens.

Here, the researchers include an overview of intensively farmed broilers’ lives:

• Eggs are laid in breeding facilities and transported to hatcheries, where they are incubated artificially for three weeks.
• After hatching, the 1-day-old chicks are transported to high-capacity rearing units which can house up to 50,000 individuals in controlled climate sheds.
• At five to seven weeks old, broiler chickens are transported to the slaughterhouse, where most waste products (feathers, manure, blood, etc.) are recycled for the production of biogas, heat or edible by-products.

Exposure To Selective Breeding

The researchers go on to explain that domestic chicken bone morphology shows that selective breeding practices took place as early as the sixteenth century. The broiler chickens that we see today, however, are a distinctive new morphotype with a relatively wide body shape, a low centre of gravity and multiple osteo-pathologies (tendency for bone diseases). In fact, if left to live to maturity, broilers are unlikely to survive, as they are dependent on intensive human intervention.

In a previous study, an increase in slaughter age from five weeks to nine weeks resulted in a seven times higher mortality rate. This was explained by the fact that the quick growth of leg and breast muscle tissues led to a relative decrease in the size of other vital organs such as heart and lungs, restricting their function and overall animal longevity. Meanwhile an alteration in the thyroid stimulating hormone receptor changed chickens’ reproduction control, enabling domestic breeds to reproduce year-round. This intense selective breeding has been proliferated by three companies, supplying 90% of broiler chicks worldwide. The process has decreased genetic diversity of broiler chickens by 50% or more compared with ancestral breeds.

Chicken Diets

Naturally omnivorous, broiler chickens have seen a change towards grain-based diets with approximately 60% of modern broiler feed composed of cereals such as maize, wheat and barley. Additions to the diet can include fishmeal and re-processed hatchery and broiler waste (e.g. egg shells, dead chicks and chickens, etc). This alteration is obviously also economically-motivated, with its end goal to reduce the amount of feed used while increasing meat yields.

The current plateau in broiler growth rates may not be maintained for too long, as a lot of ongoing research focuses on how to increase the protein intake of broiler diets by using insects as feed. Chickens already have the greatest feed efficiency of any farmed animal species, with feed conversion ratios ranging from 1.8-2 (two pounds of feed result in one pound of sold flesh) . The sheer numbers of chickens kept by humans, of course, adds up to a massive overall feed and energy consumption. It is important to note here, that the land area requirements and nitrogen emissions from the production of chicken feed is still more than twice higher than growing plant crop staples such as rice, wheat and potatoes.

Although many animal advocates undoubtedly already considered the way we manipulate farmed animals abhorrent, this study provides historical data, confirming just how much the animals we know as broiler chickens have been altered throughout the last century. Even animal sanctuaries and shelters are having hard times caring for them due to the high disease prevalence and intense care needs. Advocates can certainly appeal to the compassionate side of their fellow humans by pointing out to what extent we are mistreating these intelligent sentient beings, and how their arc through history shows just how much we’ve changed them.