Thank you for your thoughtful analysis. This is helpful for us to understand areas that must be improved or made clearer. This is especially important as we will be soon publishing  the full Welfare Footprint of the Egg (various systems), where we analyse over 120 experiences (diseases, injuries, deprivations, imbalances – nearly everything we could identify), in different housing systems, from birth to slaughter (more info here), for layers and breeders.

On your specific points on the direction of the results: there are various ways in which the existing analysis was conservative (i.e. favored caged systems). For example, in estimating the prevalence of keel fractures and other ailments in cage-free systems, we considered prevalences as they were reported, which typically was in the first few cycles of experience with cages. Evidence indicates that these prevalence rates go down as management experience increases (examples in the Prevalence Chapter), yet we preferred not to make that assumption and use the data as it was. Also, we did not take into account positive welfare (greater in cage-free settings) and more diffuse experiences, like fear, helplessness and boredom (greater in cages). Nor did we consider the flow-through effects of frustrations from behavioural deprivations beyond the period corresponding to the time budget of engagement, or practices like induced-molting (more likely in cages), or the longer cycles of caged-hens (with end disproportionally worse at the end)

Importantly, there is substantial evidence indicating that Pain is more intense (and healing delayed), even for the same injury/disease, in cages than in cage-free systems. We did not consider these modulatory effects, but they are likely present. That said, we’ll look deeper into the references you mentioned.

Unfortunately, many existing comparisons of cage and cage-free cite the CSES studies, to which the analysis from Fulton are part of. These studies were funded by the American Egg Board and facilitated by another industry-funded organization focused on building consumer confidence and maintaining the industry's viability. While management in the caged systems was good and based on decades of experience, the cage-free systems were implemented for the first time, and did not adopt nearly any of the good management practices required. For example, during the laying phase, birds in the aviary were confined for many weeks before accessing the floor litter (something that makes injurious pecking much more likely). Also, insufficient space allowance and perch space in the aviary led to crowding, collisions, and failed landings, likely contributing to the high rate of keel injury and mortality. The authors themselves declared publicly they were still learning about what to do in the aviary systems during the research, which led to many failures. These design and management failures likely substantially inflated the negative outcomes in CF systems, including mortality (mortality data is also inconsistently reported in their publications, with some mortality - e.g. during placement - apparently excluded from caged systems).

Some info that may be useful:

• Keel injuries: so far, the most consensual explanation is the earlier onset of laying, before the keel bone is ossified. This affects both cage and cage-free systems.
• Nest deprivation:  the justification for the ranges of durations and probabilities of distress intensities is provided in this chapter. These inferences are grounded in multiple lines of evidence (reviewed in the chapter). As such, they remain open to revision if new data or alternative interpretations of the evidence emerge. If you believe that the evidence supports a different intensity, please share your reasoning. This kind of scientific exchange is precisely what helps us approach values that are likely closer to reality.
• Mortality: the lack of differences in mortality is seen in many datasets, with and without beak trimming (the control mentioned in the 2021 meta-analysis is for Week’s data, not for the meta-analysis data). Industry data also shows that the best cage free systems have lower mortality than the best caged systems.  

More generally, both in the prior analysis, and in the forthcoming book, a major issue is data scarcity. Therefore, we inevitably rely on estimating uncertainty ranges for parameters like duration and prevalence. Inter-rater agreements should be made available together with future estimates, but what we have seen so far shows reasonable levels of agreement among WFI and independent academic raters/estimators.

As we build more comprehensive analyses, we’d be keen to have our estimates scrutinized as you did, so thank you!

Hi Vasco, thanks for this follow up. I believe we cannot rule out the possibilities you mentioned. That is, the answer could be yes to both questions. Even with humans, there is high variability in preference for intense but short aversiveness, as compared to moderate but longer aversion. 

One solution we have been adopting lately is to simply 'add up' times in the different categories (with no weighting or conversion). Since the 'boundaries between intensity categories' are acknowledged to be uncertain (i.e., we assign probabilities to each intensity category), adding up the time spent in different intensities follows naturally from this uncertainty. For instance, hours in Hurtful, Disabling, and Excruciating pain can be added together to report total time in 'moderate to intense pain,' or hours in Disabling, and Excruciating pain can be added together to report total time in 'intense pain'. 

Hi Vasco, that's a good question, but I do not think we can say with certainty that the ratio is preserved across species. The ratio may differ across species for a number of reasons, such as species-specific differences in the subjective perception of time. In fact, the relationship between the aversiveness of pain and its intensity may itself change dynamically for a 'same' species, depending on the duration of the experience. If on the one hand it's true that the 'criteria' defining each intensity category is universal (the same for all species), we cannot know for sure whether Excruciating pain in a shrimp is the same as Excruciating pain in a human being.
 

Thank you for this thought-provoking article, Vasco! In situations where we have clear, certain benefits in one area (here, knowing that use of slower-growing chicken breeds clearly reduces suffering for those chickens, even if their lives are longer) and a high degree of uncertainty on multiple dimensions in another (here the welfare consequences for arthropods), my inclination is that it's often more effective to focus on the suffering we are confident we can alleviate, and avoid  the non-negligible risk of relevant unintended negative consequences in the uncertain case (while simultaneously promoting further research on the latter effects). 

Hi CB, thanks a lot for your comment, I think it represents a main concern of many people. I'll break my thoughts in two parts

(1) AI use in shrimp farming and similar situations.

In this case, I understand what AI-monitoring did was to enable farmers to optimize feed use enormously (shrimp grew larger, mortality was reduced, and feed was not wasted), as well as water quality monitoring. This could be seen as negative for welfare, as it facilitates farming in high stocking densities, makes shrimp farming more profitable and could reduce prices, though this price effect is complex since the same AI technologies will likely make alternative proteins cheaper too, making the net effect on consumption less certain.

However, consider the actual conditions shrimp face. Without AI, feed distribution was uneven, leading to competition, stress, malnutrition and starvation for a large fraction of animals (mortality without AI was higher), as well as longer exposure times to poor water quality, and higher incidence of toxicities (hence respiratory distress, gill damage, skin damage) that come associated with it. This leads to suffering and higher mortality rates. So it's possible (though this should be measured) that even in higher-density environments, AI use can maintain better welfare than lower-density farms with poor feed and water quality management. Importantly , if shrimp feed relies on fishmeal and fish oil, optimizing feed reduces the number of wild fish needed, so each pound of shrimp has a smaller welfare footprint in terms of wild fish captures.

The industry trajectory also matters. Aquaculture is already moving toward higher-density and intensified farming with or without AI. So I believe the relevant comparison isn't between AI farming and a low-density or extensive scenario, but between AI-farming and conventional (intensive) high-density farming without AI. 

(2) On AI leading to greater income/prosperity, potentially increasing consumption of animal foods.

I see greater incomes and prosperity as extremely positive to reduce human suffering, but animal suffering as well. While rising incomes historically increased meat consumption, the relationship is not linear, in that as societies become more prosperous (on top of being an extraordinary thing in itself), they often can afford being more concerned with environmental and ethical issues. It's particularly in wealthier nations that we see a trend towards reduced meat consumption, stronger welfare legislation, increased interest in plant-based alternatives, and the means needed for the development of innovations like cultivated meat and other substitutes of animal protein. And again, the same technologies making animal farming more efficient are simultaneously making alternatives more competitive and affordable. I believe that the key isn't if AI increases income (something to be celebrated), but how to channel greater incomes toward ethical food systems.

Hi Vasco! Yes, it would be very interesting to collaborate on this. Right now we do not have the resources (in terms of people, and time) to do it ourselves, but we would gladly collaborate with anyone leading this effort. One possibility would be running WTP tests with people, from various demographics, to determine the extent to which they would pay to trade Disabling Pain by Hurtful Pain, or Excruciating Pain by Disabling Pain and so on (having the understanding of these intensities well explained and calibrated with examples, past experiences, etc, within a clear set of criteria).  This would help understand some level of equivalence (though from a "human" perspective) between the categories, but also generate rational WTP numbers for any estimates of Cumulative Pain (e.g., if cage-free campaigns avert X hours of Disabling Pain per hen, and people are willing to pay on average 1-10 dollars to avert one hour of this pain, you can in theory calculate the extent to which they would pay more for improved welfare, run CBA analysis, apply these to funding decisions, etc)

By not tolerated we mean that Excruciating pain can't be sustained for long (e.g., hours, as opposed to minutes) without neurological shutdown. It will tend to overrides an organism's ability to function or respond coherently, with even powerful opioids providing minimal relief, or desperate attempts to escape pain even at the risk of death . Examples would include severe burning in large areas of the body, dismemberment, or extreme torture. 
Examiing empirically trade-offs with milder pain could be interesting, but may be challenging given the nature of truly excruciating pain . Perhaps comparing to severe but more sustained pain (like bone fractures)?
 

This is indeed a legitimate concern. We do not have accurate information on the distribution of BCC-approved breeds used in the committments made so far, but I believe that organizations working on and monitoring the committments (possibly the Humane League and CIWF, which publishes the Chicken Track), are likely to have this information. From statements of company's representatives, it seems that the Hubbard breeds are prevailing in Europe, see e.g. this statement: "In Europe, where the issue of breed is more advanced than in the U.S., the Hubbard JA757, JA787 and Redbro are the main breeds used for the BCC market".

It may be interesting to know though that an experiment published recently, which used Avian Ranger Classic (the fastest growing of the Aviagen breeds), consistently showed various welfare benefits associated with this slower-growing breed, even when it was raised in higher stocking densities than the conventional fast-growing breeds (showing that it is better to be this slower-growing breed in high densities than a fast-growing breed in low densities).  

If also useful: our estimates are very conservative, and represent what we estimate to be the minimum time in pain averted with the reform. In this chapter (table 1), there is a list of welfare harms excluded from analysis, which if considered should increase further the estimated benefits of the transition to  slower growing breeds.

Thanks! I will revise the post to make sure it is clearer!

This is an interesting question, relating to the evolutionary role of pain going beyond protection of the individual survival and immediate reproduction (or that of kin), but affecting the group as a whole. As you said, debilitating pain (i.e., pain that prevents individuals to function normally) for a solitary species may also have different moral implications than for a social species even if the unpleasantness of the pain experience is the same.

My impression is that it would be difficult to determine differences in pain aversiveness among species with different degrees of sociality given the confounders present. For example, there might be differences in hedonic and cognitive capacity between social and non-social species (see eg here), hence differences in aversiveness to pain for reasons other than the context of the painful experience.