I feel like chicken tonight

Jenny Love, UCL Energy Institute

Lizzy Love, Department of Biology, University of Leeds

In case you can’t tell from the title, this article is about the trade-off between efficiency, general sustainability and animal welfare in meat production.

Meat is a very energy and resource intensive good to produce. The use of intensive farming can reduce the need for energy, space, feed, chemicals and other inputs, but often at the expense of the welfare of the animal. Is it always the case that efficiency and animal welfare are at odds?

First of all we’ll examine what we might mean by efficiency. We’re going to have an imaginary Green Champion competition between our favourite farmyard animals, taking into account more factors as we go along.

1. Feed conversion efficiency

The normal definition of efficiency is:

Efficiency = Useful Energy Output / Total Energy Input

There is an equivalent in the meat industry for an animal: the efficiency with which an animal can convert feed eaten into increased body mass.

Feed Conversion Efficiency = Kg Weight Gained / Kg Feed Eaten

Here’s how the animals fare:

Poultry: 1/1.5

Pig: 1/3.5

Cow: 1/7

This definition is basically about animals’ digestive systems. The large difference between poultry/pigs and cows/sheep is the distinction between ‘simple-stomached’ animals and ‘ruminants’. The former can eat food packed with energy, like cereal, and immediately convert it to meat. There isn’t a limit to the energy density of the food you can give them – although we’ve never seen a chicken on Lucozade or Kendal Mint Cake.  The latter group cannot tolerate these foods, instead eating fibrous matter and undertaking a complicated cycle of fibre breakdown and conversion, which cannot be sped up by increasing the energy in the food.

One reason the efficiency of ruminants is so low is the energy cost of producing waste gases (methane, CO2 and hydrogen). In cows, 5-15% of gross dietary energy (ie feed) is lost through conversion to methane! Apparently, cows can ‘eructate’ 30 litres of gas per day. We’ll leave you to work out what ‘eructate’ means.

However, this definition of efficiency does not take into account the nature of the feed – namely, the energy taken to produce it. Cows and sheep do have something going for them: in places where the quality of what can be grown is low, they are the only animals which can still produce meat…

2. Land use efficiency

Sometimes, despite the poor feed conversion efficiency of cows and sheep, it is efficient to put them in a field. If the quality of the terrain is so low as to only be able to grow grass, there’s not a lot our digestive system can do with it even if we are hungry. However cows and sheep come to the rescue, with their superior mechanisms for converting low-quality feed into meat. We, simple-stomached, stand in awe.

This parallels with the concept of energy – the usability of energy. There is a lot of energy in the field of grass, but to me there is none as we can’t convert it into a usable form. Stick a couple of sheep in there, let them convert the energy for us, and even though their conversion losses are high, we can still get some energy from my field by eating them.

If there is potential to grow higher quality feed than grass on the field, such as cereals, here is a different ball game. It is much more efficient for humans to grow cereals for their own consumption than to grow cereals for feed for pigs and poultry. About half of all grain produced worldwide is used as animal fodder to sustain our demand for meat.

3. LCA (Life Cycle Assessment)

This is the most all-encompassing of the sustainability indices. So far, we’ve considered a narrow definition of energy efficiency, where chickens took a sprint start, and a wider definition of getting the most energy from land, which caused cows and sheep to catch up in some situations. However, there are many other factors we should care about: biodiversity loss, global warming potential, eutrophication, resource depletion, etc…

Life Cycle Assessment is a way of weighing up the environmental cost of as many of these factors as possible, and has been done a few times for animal products. We’re not going to dwell on LCA here since it’s very complicated – if you want to know more then here’s an example of LCA comparing conventional and organic milk production: http://www.sciencedirect.com/science/article/pii/S095965269900311X

In our Green Champion competition, LCA has made everything more complicated so we don’t quite know how all the various animals came out. However, we’re still not finished –  there is one thing that all LCA analysis of meat we’ve seen so far misses…

4. Animal welfare

There are basically 4 levels of welfare standard for meat production in the UK:

The minimum legal UK requirements

This standard is better than most other European countries, and much better than many non-EU countries, but still not saying much. For example, pigs are never legally required to go outside once in their lives from birth until slaughter – they can be housed indoors on wooden slatted floors with no straw to nest in and relatively small amount of space with no natural daylight. PIgs are naturally intelligent animals and these conditions lead to boredom and consequent vices such as tail biting (chewing the tails of other pigs until it draws blood which in turn attracts other pigs to do the same) and bullying.

A second example is poultry – caged hens are still allowed – these produce eggs and eggs and eggs…then are killed …not much of a life! Being kept in a cage all their working life in cramped conditions causes them pain due to leg problems. In chickens used for meat, these painful leg conditions have been worsened by genetic breeding programmes to increase the weight of the chicken (more efficient as each chicken produces more meat – but its legs are too weak to support its own weight without huge discomfort).

Red tractor scheme

A picture of a tractor makes us feel warm and fuzzy about our sausages but this standard is actually not much better than the legal minimum. Don’t be fooled. For example, pigs are still not required to go outdoors and they still do not require straw bedding to nest in.


RSPCA freedom foods: http://www.rspca.org.uk/sciencegroup/farmanimals/standards

A big step up in terms of ‘natural’ conditions – for example pigs now do have to have deep clean straw beds – but there is still no requirement to give animals access to the outside.

Organic, e.g. soil association certified

Some of the requirements of this standard include access to outside, a natural organic diet, and the restriction of use of drugs to illness only.

Here are some efficiency and welfare implications of the standards. These are by no means all the issues in the debate:

-          SPACE: Having space is all very well, but chickens actually don’t like going outside much. However, having a choice could be seen as important.

-          DISEASE: Being kept outside increases exposure to disease – and organic farming prohibits vaccination. So is ‘welfare’ decreased with organic farming? It depends what you mean by welfare…

-           STUPIDITY: A major killer for piglets, would you believe, is being accidentally rolled on by their mother. It’s a mystery that pigs haven’t evolved themselves out of the ecosystem yet. Intensive farming involves much more supervision and prevention of such idiotic acts.

-          EMISSIONS: Intensive farming allows each animal to make more meat/milk/eggs. It is argued that organic farming has a worse carbon, nitrogen and water footprint than conventional farming.

-          WASTE: Intensive farming does use animal waste, thus preventing it from going into rivers and causing eutrophication, but the collection method in the Red Tractor and Minimum Legal standards involves slatted floors which are hardly comfortable for the animals to live on.

-          LEGISLATION: Arguably intensive farming is easier to regulate compared to extensive.

-          SOIL: Keep animals outside and not only do they take up a lot of space but they also trample around on the soil and cause the nutrients to leach out.

Given the above, it appears that chickens’ welfare is compromised the least when produced intensively, for pigs it depends what we mean by welfare, and for cows and sheep they need their space.

We give the Green Champion award to chickens.

5. Conclusion

What a minefield of considerations before you decide what to eat. However the following is what we, the authors, would personally advise in conclusion. We certainly haven’t mentioned every aspect so feel free to comment and ask us questions and we’ll try to answer.

-          Cut down your meat intake. If you’re very careful you can eat none, if you’re not so careful then eating meat twice a week should give you sufficient nutrients. In general the order of efficiency is chickens/turkeys, pigs, cows/sheep.

-          Buy meat less often but ensure that the meat is from high welfare standards: preferably organic, but at least RSPCA freedom foods. Make sure it’s UK meat – not only for welfare reasons but also food miles.

-          Read packaging extremely carefully – manufacturers can be very devious, displaying statements such as, “Farm Fresh” (means nothing), “British meat” (means minimum legal standards), and, “produced in the UK” (using chicken from Thailand).

-          Eat meat products which are oversupplied, such as liver. (This is one of the most nutritious foods you can possibly eat, and it is very cheap). In this way you can eat meat without increasing demand for it.

-          When you buy processed food (pasties, pies…), it’s likely that the welfare standards are lower.

-          Remember the benefits of eggs – their production is efficient without compromise of welfare (but please don’t buy eggs from caged hens), they contain pretty much the same nutrients as meat (all of the essential amino acids in the right profile so can be absorbed and utilised), and once chickens have stopped being efficient at laying they get used for meat.

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6 thoughts on “I feel like chicken tonight

  1. On eggs: The problem comes when buing cakes etc. which are ready-made, and probably use the lowest wefare (i.e. cheapest) eggs available. Is there any sort of marking scheme to deal with this? I’ve heard that the co-op’s own branded stuff only uses “friendly” eggs, but haven’t looked into it.

    • Hi, Lizzy tells me that there’s a double-standard here:
      - Everything at the Co-op using eggs as an ingredient uses free range eggs;
      - But if you pick up a chicken sandwich, you’ll see that the chickens are from Thailand (i.e. probably the lowest possible welfare standards).

      So there’s a difference between chickens for eggs and chicken for meat. How interesting.

  2. I work at co-op so will have a look next time I am in work.
    I do know that Mr Kipling now only uses free range eggs!

  3. Pingback: How GREEN is your Christmas tree this year? | energyandlife

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