Commercial broiler production represents some of the most serious animal welfare issues in the livestock industry. Over the last years, campaigns to improve the way broiler chickens are produced, including the use of slower-growing broiler strains, have been gathering pace in many countries. Currently, one of the leading standards for broiler welfare driving the food industry towards higher welfare practices is the Better Chicken Commitment (BCC), a set of recommendations that address housing, stocking density, growth rate and stunning methods.
In this project, we used the Cumulative Pain Framework to investigate how the adoption of the BCC and similar welfare certification programs affect the welfare of broilers. Specifically, we examine concerns that the use of slower-growing breeds may increase suffering by extending the life of chickens for the production of the same amount of meat.
The framework translates evidence on the duration and intensity of the pain associated with these challenges into time spent in four categories of pain intensity: Annoying, Hurtful, Disabling, and Excruciating. Pain is operationally defined as ‘any negative affective state’, thus encompassing negative affective experiences of both somatic origin (physical pain) and more related to the primary emotional systems (psychological pain). By considering the prevalence of each welfare challenge in the population, estimated times in pain are also determined for the average population member (in this case, the average commercial broiler). The method is transparent, brings important knowledge gaps into light, and incorporates uncertainty about all parameters into the final estimates.
We analyzed the following scenarios, for which data on broiler welfare was available. First, a conventional scenario represented by the use of fast-growing breeds (e.g., Aviagen Ross 308, 708, Cobb 500). Although the performance objectives of these breeds can reach as much as 70 g/day, with birds weighing 2.5 Kg in 35 days, average slaughter weight of broilers in the EU and the US is, respectively, 2.5 Kg and 2.9 Kg, reached at 42 and 47 days. This corresponds to an average daily gain (ADG) of 60 and 62 g/day, respectively. We used these values as a benchmark for typical growth rates in fast-growing strains, assuming an ADG of 61 g/day, corresponding to a slaughter weight of 2.5 Kg at 42 days. For the reformed scenario, represented by the use of a slower-growing strain, we assumed an average ADG of 45-46 g/day, hence that the same slaughter weight would be reached in approximately 56 days. This is a growth rate consistent with typical figures achieved by various of the breeds approved under the BCC (e.g. JA 987, 787, Ranger Gold), also referred to as medium- or intermediate-growing broilers. This growth rate also falls within the acceptability of other welfare certification schemes, such as the ‘Beter Leven’ program in the Netherlands and the ‘Deutsche Tierschutzbund’ in Germany, which determine a growth rate of up to 45 g/day, and a minimum lifespan of 56 days. Importantly, data on the incidence of important welfare challenges in slower-growing breeds (e.g. proportion of birds with different degrees of lameness) is available predominantly for birds growing at approximately this rate.
In both scenarios, we focused on key welfare challenges affecting broilers: gait-impairing conditions (lameness), cardiovascular problems, thermal stress, the frustration potentially arising from the deprivation of various motivated behaviors, chronic hunger in broiler breeders and the welfare harms endured during stunning and slaughter. This is, however, not an exhaustive list of every welfare harm affecting broilers, hence Cumulative Times in Pain underestimate the typical times in pain endured by broilers in commercial production. Because the welfare harms not considered (e.g. infectious diseases, inflammatory conditions, contact dermatitis, muscle abnormalities, additional negative effects of feed deprivation in conventional breeders other than chronic hunger) have a higher incidence in fast-growing birds, the estimates presented are conservative, representing the minimum time in pain expected to be averted with implementation of the BCC and similar standards.
A summary of key findings is available below. They have been also featured by Our World in Data.
Experiences of pain perceived as aversive, but not intense enough to disrupt the animal’s routine in a way that alters adaptive functioning or affects the behaviors that animals are motivated to perform. Similarly, Annoying pain should not deter individuals from enjoying pleasant experiences with no short-term function (e.g., play) and positive social interactions. Sufferers can ignore this sensation most of the time. Performance of cognitive tasks demanding attention are either not affected or only mildly affected. Physiological departures from expected baseline values are not expected to be present. Vocalizations and other overt expressions of pain should not be observed.
Experiences of pain in this category disrupt the ability of individuals to function optimally. Different from Annoying pain, the ability to draw attention away from the sensation of pain is reduced: awareness of pain is likely to be present most of the time, interspersed by brief periods during which pain can be ignored depending on the level of distraction provided by other activities. Individuals can still conduct routine activities that are important in the short-term (e.g. eating, foraging) and perform cognitively demanding tasks, but an impairment in their ability or motivation to do so is likely to be observed. Although animals may still engage in behaviors they are strongly motivated to perform (i.e., exploratory, comfort, sexual, and maintenance behaviors), their frequency or duration is likely to be reduced. Engagement in positive activities with no immediate benefits (e.g., play in piglets, dustbathing in chickens) is not expected. Reduced alertness and inattention to ongoing stimuli may be present. The effect of (effective) drugs (e.g., analgesics if pain is physical, psychotropic drugs in the case of psychological pain) in the alleviation of symptoms is expected.
Pain at this level takes priority over most bids for behavioral execution and prevents all forms of enjoyment or positive welfare. Pain is continuously distressing. Individuals affected by harms in this category often change their activity levels drastically (the degree of disruption in the ability of an organism to function optimally should not be confused with the overt expression of pain behaviors, which is less likely in prey species). Inattention and unresponsiveness to milder forms of pain or other ongoing stimuli and surroundings is likely to be observed. Relief often requires higher drug dosages or more powerful drugs. The term Disabling refers to the disability caused by ‘pain’, not to any structural disability.
All conditions and events associated with extreme levels of pain that are not normally tolerated even if only for a few seconds. In humans, it would mark the threshold of pain under which many people choose to take their lives rather than endure the pain. This is the case, for example, of scalding and severe burning events. Behavioral patterns associated with experiences in this category may include loud screaming, involuntary shaking, extreme muscle tension, or extreme restlessness. Another criterion is the manifestation of behaviors that individuals would strongly refrain from displaying under normal circumstances, as they threaten body integrity (e.g. running into hazardous areas or exposing oneself to sources of danger, such as predators, as a result of pain or of attempts to alleviate it). The attribution of conditions to this level must therefore be done cautiously. Concealment of pain is not possible.
Although pain inherently concerns individuals, we operationally accept that the collective welfare of the members of a population can also be determined. Measuring cumulative pain at the population level is also necessary to account for the heterogeneity in the exposure of population members to different challenges. For example, while lameness is experienced by a large fraction of broiler chickens, fatal cases of ascites are only experienced by a few. Therefore, measurement efforts must consider the prevalence of each welfare challenge, so that pain is determined for the average member of the population (which may not necessarily correspond to any real organism). At the population level, the time spent at each level of pain intensity as a result of each challenge is determined by multiplying it by its prevalence. For example, if a condition causes 10 hours of Disabling pain and 70% of the population are affected, then the average member of this population could be said to experience 7 hours of Disabling pain due to the condition. Measurements at the population level enable comparing the impact of different practices and conditions across demographics, geographies, and time.
All methods, assumptions, justifications and results are discussed thoroughly in the book “Quantifying pain in broiler chickens”, available below and on Amazon.
All parameter values used for the analysis (estimates of duration, intensity, number of occurrences, and the prevalence of each welfare offense) are justified in the book “Quantifying Pain in Broilers” (see above). However, we invite the reader to examine the extent to which the estimates presented here are sensitive to our choices and assumptions, at the platform https://pain-track.org/broilers. In this web application, all parameter values can be altered, with the automatic update of all estimates.
