Animal Welfare Implications of Silk and Wool

Silk fine, wool meh

Content note: explicit descriptions of animal suffering.

The research that led to this blog post was commissioned by Miranda Gavrin. If you would like to commission me to research a topic for you, please email me at ozybrennan@gmail.com.

Silk

Silk is fine.

It takes about 2,500 silkworm individuals to produce a pound of silk, according to this random silk company I have no reason to doubt. Silkworms live for about six weeks, so there are about 105,000 silkworm-days per pound.¹

That sounds like a lot. But the Moral Weights Project’s point estimate is that an hour of silkworm suffering matters as much as about seven seconds of human suffering. The 90% confidence interval is between silkworms not mattering at all and 4.38 minutes of human suffering. So a pound of silk requires between zero and 7,655 human-equivalent silkworm-days, with a point estimate at 210 days.

Still kind of a lot. But silkworm lives seem, according to Rethink Priorities’ paper on silkworm welfare, to be… fine? They seem to live a perfectly ordinary, natural life, eating an enormous amount of mulberry leaves (apparently over the course of their lives they eat 50,000 times their original weight in mulberry leaves). They do suffer from a high death rate due to disease: between 10% and 47% of silkworms die of disease.² But I don’t think that outweighs all the other silkworms that seem to be perfectly happy.

Now, producing silk does involve boiling silkworm pupae alive. However, it’s not clear that silkworm pupae even have neural tissue at that point, much less the ability to suffer. Even if slaughter is painful, it’s relatively brief, lasting only a few minutes.

I personally feel it is fine to consume silk. I have a lot of uncertainties about silk, but I can imagine resolving them in either direction: it might be bad to consume silk because the diseases are particularly nasty, but it might also be good to consume silk so that there are more happy silkworms living happy silkworm lives consuming mulberry leaves in enormous quantities.

Wool

The Moral Weights Project doesn’t have a specific estimate for sheep, so I would use pigs as a proxy. One hour of human suffering is equivalent to half an hour of sheep suffering (90% confidence interval: 18 seconds, equivalent). A sheep produces two to thirty pounds of wool per year, which means that there are 12 to 180 individual-days per pound of wool. The point estimate is 48 human-equivalent individual-days per pound.

In this section, I am talking only about wool sheep. I am not talking about sheep raised for milk or meat. Sheep raised for milk and meat live in different conditions which I tentatively expect to be worse.

Wool sheep are generally extensively farmed. Extensive farming is the peaceful grazing on vast expanses of pasture which you may know from children’s picture books; intensive farming is the torturous hellscape which you may know from Mercy for Animals undercover investigations.

Extensionally farmed sheep in New Zealand. By © Jorge Royan, CC BY-SA 3.0

Wool sheep, like most extensively farmed animals, generally live a lifestyle similar to the lifestyle they evolved for. They spend most of their time outdoors and get most of their nutrients from pasture. As extensively farmed animals, they usually have the chance to perform a wide range of species-appropriate behavior, such as flocking with other sheep, spending time with favored individuals, grazing, and so on.

However—particularly if the stockpeople don’t take good care of them—wool sheep can also face the downsides of a wild-typical lifestyle, such as hunger, excessive heat or cold, predation, and accidents. Typically, stockpeople will ensure their sheep have enough food, only raise sheep in relatively safe places with broadly reasonable weather for sheep,³ etc.

Of particular concern is disease. Because stockpeople only rarely interact with sheep, it’s difficult for them to tell whether sheep are sick. It’s likely that the prevalence of many wool sheep diseases is underestimated. The most common serious health issue for sheep is lameness. This paper roughly estimates that more than 80% of flocks have at least one lame sheep, with lameness affecting a fifth or more of sheep in some flocks.

Sheep are normally handled several times a year for medical purposes, shearing, and movement from pasture to pasture. Sheep are anxious and easily frightened, especially by novel experiences. Wool sheep rarely encounter humans and so find their presence inherently frightening. Most of the things humans do to sheep are also frightening to sheep: shearing, veterinary care, restraint, etc. However, gentle stockpeople can reduce the sheep’s fright; sheep have very good memories.

The most unpleasant routine experience for sheep is shearing, which happens once a year. Sheep typically fast for 24 hours before shearing. Sheep can be nicked or cut during shearing, especially with an inexperienced, distracted, or rushing shearer. These cuts can be deep enough to require stitches.

Nevertheless, these experiences make up a relatively small fraction of a sheep’s daily life, most of which is spent living in a relatively pleasant manner without human disturbance.

The most serious welfare concerns for wool sheep, in my opinion, occur early in life: mulesing, tail docking, and castration. In this section I draw heavily on reports from the Farm Animal Welfare Council and the British Animal Welfare Committee. Most sheep operations practice routine castration of males and tail docking (removal of the tail). Castration prevents the production of unwanted offspring, while tail docking is believed to reduce the risk of a painful disease called flystrike⁴ (although evidence supporting this claim is mixed).

Both tail docking and castration are typically performed using the “rubber ring method”: a thick, tight rubber ring is placed around the body part, which cuts off the blood supply to the part. The part will fall off and die within a few weeks. Both procedures are typically performed without any sort of pain relief.

Castration is believed to be extremely painful. The acute pain from the rubber ring method of castration typically lasts about two hours. Studies suggest that lambs experience chronic pain for four to five weeks after castration, until the area fully heals. Tail docking is believed to be less painful than castration, but still to be very painful. Tail docking often occurs at the same time as castration, which may be more painful than either individually. Tail docking sometimes results in long-term chronic pain and other health complications, although we have limited evidence about this topic. 

Both castration and tail docking involve significant handling, which tends to be distressing for sheep. 

Merino sheep from Australia (the practice is being phased out in New Zealand) also undego mulesing, the removal of skin from around their tail. Mulesing is also very painful. A topical painkiller is typically applied afterward, but it is usually not applied before the surgery and it provides only eight hours of relief. Although mulesing also is believed to protect sheep from flystrike, it is in fact unnecessary.

Wool sheep are slaughtered at slaughterhouses at six or seven, when their wool productivity begins to decrease. Slaughterhouses are extraordinarily unpleasant for sheep: all methods of stunning are prone to failure, which leaves the animal conscious while they slowly bleed to death. However, my guess is that people eating wool sheep likely displaces them eating meat sheep, which are more likely to be raised in intensive farms, so plausibly the slaughter of wool sheep is net-positive for animal welfare.

Textile Exchange certifies wool (alongside other animal products, such as down). I primarily looked at Materials Matter standards, which will be fully implemented in 2026. Textile Exchange’s standards seem to be generally appropriate to ensure a high level of sheep welfare, and in general I would feel ethically comfortable with purchasing Textile-Exchange-certified wool.

My primary concern is that Textile Exchange permits tail docking and castration without pain relief. I wouldn’t want to forbid tail docking and castration entirely: unlike mulesing, these practices can be net-beneficial for the sheep’s welfare. And Textile Exchange does require that pain relief be used if the country the farm is in has approved a painkiller for sheep. I think this is probably the best of the bad options, but if you would prefer that your sheep not be tortured at all, you shouldn’t buy wool.

Fake numbers time! I took Brian Tomasik’s How Much Direct Suffering Is Caused By Various Animal Foods? and replaced the sentience weights with the Moral Weights Project’s point estimates, for comparability. Tomasik set 1 to be equivalent to beef cows, and I think wool sheep are comparable to somewhat better off than beef cows, so I tried 0.5 and 0.9 as a sort of fake sensitvity analysis. In terms of suffering per kilogram demanded, wool is somewhere between chicken and turkey, although notably a kilogram of wool lasts much longer than a kilogram of turkey.

However, Tomasik’s calculator doesn’t allow for the possibility that animals have positive welfare, which I think is plausible for Textiles-Exchange-approved wool sheep that have pain relief during surgery.⁵ In that case, wool would be fine or even morally good to consume.

1. As silkworms lay 300-400 eggs, I expect parental silkworms to make a negligible contribution to this number.

2. I’m not sure if the random silk industry website’s numbers include silkworms dead from disease; if it does, this would increase the number of silkworm days involved.

3. Sheep can handle a range of temperatures and are fine in most environments that one might raise a sheep in.

4. In flystrike, fleece near the buttocks traps feces, which attracts fly larva, which eat away at the sheep’s flesh. The sheep die three days to a week later from ammonia poisoning.

5. And, for that matter, for beef cows.