Demographics for all four breeds of broiler chickens

In 2018, over nine billion chickens were slaughtered in the United States.
As the demand for chickens increases, so too have concerns regarding the
welfare of the chickens in these systems and the damage such practices
cause to the surrounding ecosystems. To address welfare concerns, there is
large-scale interest in raising chickens on pasture and switching to
slower-growing, higher-welfare breeds as soon as 2024. We created a box
model of US chicken demographics to characterize aggregate broiler chicken
welfare and land use consequences at the country scale for US shifts to
slower-growing chickens, housing with outdoor access, and pasture
management. The US produces roughly 20 million metric tons of chicken meat
annually. Maintaining this level of consumption entirely with a
slower-growing breed would require a 44.6%–86.8% larger population of
chickens and a 19.2% – 27.2% higher annual slaughter rate, relative to the
current demographics of primarily “Ross 308” chickens that are slaughtered
at a rate of 9.25 billion per year. Generating this quantity of
slower-growing breeds in conventional concentrated animal feeding
operations (CAFO) would require 90,582-98,687 km2, an increase of
19.9-30.6% over the 75,577 km2 of land used for current production of Ross
308. Housing slower-growing breeds on pasture, the more individually
welfare-friendly option, would require 108,642-121,019 km2, a 43.8-60.1%
increase over current land use. Allowing slower-growing breeds occasional
outdoor access is an intermediate approach that would require
90,691-98,811 km2, an increase of 20-30.7% of the current land use, a very
minor increase of land relative to managing slower-growing breeds in
CAFOs.  In sum, without a drastic reduction in consumption,
switching to alternative breeds will lead to a substantial increase in the
number of individuals killed each year, an untenable increase in land use,
and a possible decrease in aggregate chicken welfare at the country-level
scale. Pasture-based management requires substantial additional land use.
These results demonstrate constraints and trade-offs in animal welfare,
environmental conservation, and food animal consumption, while
highlighting opportunities for policies to mitigate impacts in an
integrated manner using a One Health approach.