On the welfare effects of slower growing breeds, I think suffering is reduced overall despite the increase in life expectancies, based on Welfare Footprint Institute’s analysis:
Adoption of the Better Chicken Commitment, with use of a slower-growing breed reaching a slaughter weight of approximately 2.5 Kg at 56 days (ADG=45-46 g/day) is expected to prevent “at least” 33 [13 to 53] hours of Disabling pain, 79 [-99 to 260] hours of Hurtful and 25 [5 to 45] seconds of Excruciating pain for every bird affected by this intervention (only hours awake are considered). These figures correspond to a reduction of approximately 66%, 24% and 78% , respectively, in the time experienced in Disabling, Hurtful and Excruciating pain relative to a conventional scenario due to lameness, cardiopulmonary disorders, behavioral deprivation and thermal stress.
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In general, the slower the growth rate, the shorter the cumulative time in pain experience over a lifetime, despite differences in lifespan. Should breeds with growth rates slower than those assumed in the reformed scenario be used, the time in pain averted with the reform would be longer, despite a longer lifespan. By the same logic, slower-growing breeds growing faster (e.g. 50g/day) should endure a longer time in pain, despite their shorter lifespan. In all cases, reforms promoting a transition to slower-growing breeds should expect a reduction of the cumulative time in pain (net positive change) for all breeds considered under the BCC scheme: the slower the growth rate, the higher the expected welfare impact.
On the welfare effects of slower growing breeds, I think suffering is reduced overall despite the increase in life expectancies, based on Welfare Footprint Institute’s analysis: