Hi Amanda, thank you for your thoughtful analysis. I do believe taking a step back and scrutinizing the evidence and direction where we’re heading is extremely important, and I agree with your conclusion that increasing R&D and talent is very much needed. I also agree that the evidence gaps are enormous. As a research group working specifically to address them, we’re very much aligned. In that same spirit, I share some considerations below on the cage-free transition example, into topics to make the text lighter.
The problem with the CSES study as a reference for mortality / welfare conclusions.
The CSES study is a highly cited reference for the argument that cage-free aviaries are not necessarily better. It was funded by the American Egg Board and facilitated by another industry-funded organization focused on building consumer confidence and maintaining the industry’s viability. Unfortunately, this study had multiple design flaws and biases in favor of cages (a more detailed analysis, done some years ago, is available here). A few examples:
Several observations point to stockmanship being ‘very deficient’ in the aviary (the farmer had never managed one), but not in cages, with which the farmer had decades of experience. Inspection frequency also seems to have been higher in cages.The research authors themselves declared they were still learning about what to do in the aviary during the research, which led to multiple failures. In fact, inspection was so infrequent/deficient that a large fraction of dead birds were found in advanced stages of decomposition.
Vet/disease treatment was employed for cages, but not aviaries
The overwhelming majority (~90%) of good practices for cage-free aviaries were *not* adopted (e.g., aviary chicks were raised in cages, with no development of skills to perch or navigate the aviary, densities were higher than typical, laying birds in aviaries were confined for hours every day, increasing the risk of feather pecking, breeds adapted for decades to cages were used in aviaries, chicks did not have access to litter, among many others poor management decisions—see a summary table in this document)
Key practices to reduce the risk of feather pecking / cannibalism in aviaries were not used (in fact, CSES management choices are known to promote these issues).
CSES mortality data does not add up, there are multiple inconsistencies in the dataset and in the mode of data collection/reporting, discussed here.
Mortality Data
Farm animal welfare in natural and more extensive systems, including cage-free aviaries, depends more heavily on good management practices and stockmanship. As such, we should expect greater variability in terms of mortality, as well as greater absolute mortality in the first production cycles following a transition. For this reason, the fact that there is a greater number of orange cells (mortality higher in aviaries) in the datasets of the meta-analysis is expected, as most are comparisons of established caged systems with newer cage-free systems. The studies span two decades during which cage-free systems underwent major changes. This is why we explicitly modeled the year of data collection as a predictor. Mortality rates are changing systematically over time. Modeling that trend directly, and then reporting recent mortality separately, is necessary for relevance. Another point is that brown-feathered genotypes (associated with higher mortality) are more common in cage-free systems, naturally increasing mortality because of breed, not system.
The data below, from an internal database from a breeder for countries around the world (in 2018), can also be useful.
Mortality as an indicator of welfare
Mortality may or may not correlate well with welfare. It is widely used because it is easy to measure, routinely collected, and economically important. However, mortality captures whether animals survive, not what their lives are like while they are alive.
The industry is often very good at keeping animals alive and productive until the end of the production cycle, even under conditions associated with extremely poor health and welfare (what we refer to as the “hospital bed effect”). Conversely, some more extensive or naturalistic systems may have higher mortality because animals are exposed to more hazards. Healthy pasture-raised animals, for example, may experience higher mortality due to predation. There may often be a trade-off between behavioral freedom and protection from mortality risks (‘children who never play outdoors are less prone to injuries and fatal accidents’, yet few would argue this is better for their well-being).
Mortality is most informative when comparing otherwise similar systems. When comparing systems that differ fundamentally in housing and behavioral opportunities, mortality should be interpreted together with other welfare metrics.
Life Quality/Well-being in cages x cage-free
The 2021 WF analysis was very conservative (i.e. favored caged systems) in a number of ways as we discussed in the book and elsewhere. For example, we considered prevalence for ailments in cage-free systems as reported, without any adjustments for improvements over time (despite evidence that the frequency of various harms was going down, similar to mortality).
Also, we did not consider positive welfare (opportunities are naturally more frequent in cages) nor the longer lifecycle of caged hens (welfare is typically worse at the end of life), and end-of-life events such as induced molting, still practiced in many countries in caged systems.
We also did not consider the negative impacts of learned helplessness, lack of agency, and depression-like states in cages—there is now new evidence for such depressive states in caged hens.
Importantly, we did not make any adjustment for what I believe to be robust evidence that the pain from an injury or disease is perceived as more intense and longer in cages than in cage-free systems. Barren, confined environments disable multiple endogenous analgesic mechanisms while simultaneously activating several neurobiological pathways that intensity nociceptive signaling and delay healing. Should that be taken into account, it would further reduce time and intensity of pain in cage-free aviaries.
Fear in Cages vs Cage-free systems
Several studies have found that hens reared or housed in cage-free systems are less fearful than hens kept in conventional cages. Aviary-reared birds show reduced fear responses in tonic immobility, novel object, and novel environment tests, spend more time near humans and novel objects, use elevated areas more readily, and perform better in spatial memory tasks than cage-reared birds (Hansen et al., 1993; Tahamtani et al., 2015; Brantsaeter et al., 2016). They suggest that the more complex environments in cage-free systems may reduce fearfulness and improve behavioural adaptability. See box 9.2 of the laying book for more details.
Behavioural and Physiological Indicators as a standard for welfare-related decisions
Welfare is multidimensional, and cumulative experience matters. So unfortunately no single behavioural or physiological measure, or restricted set of measures, can provide a complete picture of welfare, nor even for humans (for which calibration is possible). Behavioral, immunological, neurological, and physiological measures are valuable for inferring states associated with specific experiences, often at specific points in time. However, they are insufficient for overall welfare assessments, as well as confounded by multiple factors, and more reliable for acute rather than chronic harms (particularly immunology and physiology). Because they are typically species-, harm- and context-specific, they also do not enable comparisons across harms, systems and species. Several attempts have been made in recent years to design an umbrella measure of welfare (e.g., telomere length, cognitive bias tests), but so far unsuccessful. That’s not to say indicators are not useful: we rely heavily on them for our work, and believe having more monitoring systems and research would be extremely needed. But for overall welfare assessments and system comparisons as in the case of cage-free transitions, we need welfare metrics, which integrate evidence from multiple welfare dimensions, providing a stronger basis to infer cumulative experience. In case it’s useful, here we discuss in more detail the differences between welfare metrics and welfare indicators.
Thank you again for this critical analysis!
Cynthia
Hi Vasco, my sense is that moving from cages (even if furnished)to cage-free aviaries is an improvement, for the reasons I mentioned in my earlier response. Right now, with the evidence gaps there are, it’s very hard though to make a reliable distinction between 10th percentiles.