18.11 Making Food Production Efficient

A free GCSE Biology lesson for AQA (8461) from OBA School: shorter food chains, intensive farming of animals, and the ethical issues involved. Watch the video, read the explanation and worked examples, then try the revision questions. You can work through the full lesson, with every video, practice quizzes and printable worksheets with mark schemes, in our free online course.

What you will learn

• Explain why shorter food chains can feed more people
• Explain how limiting movement and controlling temperature increase the efficiency of meat production
• Explain why some animals are fed high-protein foods
• Evaluate intensive (factory) farming, including ethical objections
• Carry out calculations on feed, growth and efficiency

Key words

• Intensive farming: Rearing animals in controlled conditions indoors, often close together, to produce as much food as possible from the feed given.
• Factory farming: Another name for intensive farming of animals.
• Free-range: Animals that can move around outdoors for at least part of the day.
• Feed conversion ratio: The mass of feed needed for an animal to gain 1 kg of body mass. A lower ratio means more efficient conversion.
• Ethics: Ideas about what is morally right or wrong, e.g. about how animals should be treated.

Shorter food chains

Biomass is lost at every step of a food chain (18.9). If people eat plants directly, instead of feeding the plants to animals and then eating the animals, far more of the original biomass becomes human food.

Meat and dairy are still important sources of protein and other nutrients, and some land (e.g. steep hills) is better for grazing than for crops. But eating less meat would help feed a growing population.

Reducing energy transfer to the environment

Animals use a lot of the glucose they eat for respiration, to move and to keep warm. The energy released is transferred to the surroundings and does not end up as new biomass. In intensive farming the farmer reduces these losses:

• Limit movement (small pens or cages); Why it increases efficiency Less energy is needed for muscle contraction, so less glucose is respired. More biomass goes into growth.
• Control the temperature (warm sheds); Why it increases efficiency Animals use less energy to keep their body temperature constant, so more biomass goes into growth.
• Feed high-protein food; Why it increases efficiency Protein provides amino acids for building new tissue, so animals grow faster.

Worked example: feed for a flock

Indoor chickens need about 1.8 kg of feed for each 1 kg they gain. A farmer rears 5000 chickens, each gaining 2.2 kg.
Total gain = 5000 × 2.2 = 11 000 kg
Feed needed = 11 000 × 1.8 = 19 800 kg

Answer: 19 800 kg of feed (19.8 tonnes)

Is intensive farming right?

• More meat produced from the same feed; Disadvantages and ethical objections Animals cannot move freely or behave naturally; many people think this is cruel
• Cheaper food, so more people can afford protein; Disadvantages and ethical objections Disease spreads quickly between animals kept close together
• Less land needed than free-range farming; Disadvantages and ethical objections Antibiotics are often used, which can lead to antibiotic-resistant bacteria
• Animals protected from predators and bad weather; Disadvantages and ethical objections Heating and lighting sheds uses a lot of energy (fossil fuels); waste can pollute water

Exam tip: For “evaluate” questions on factory farming, give points about efficiency and cost, then ethical, health and environmental points, and finish with a conclusion.

Common mistakes

• Saying animals in warm sheds “don’t need energy”. They still respire, but use less energy to keep warm, so more biomass goes into growth.
• Saying restricted animals “get fatter because they are lazy”. Explain that less glucose is used in respiration for movement.
• Forgetting the ethical side. Many exam questions ask about animal welfare, disease and antibiotic resistance.
• Multiplying the wrong way in feed calculations: feed needed = mass gained × kg of feed per kg gained.

Revision questions

Try these, then check your answers below each one.

Question 1. Why do intensive farmers keep animals in warm sheds? (Choose from: Warm air contains more protein, Less energy is used to keep warm, so more biomass goes into growth, Warmth stops the animals respiring, Animals eat less food in the cold.)

Answer: Less energy is used to keep warm, so more biomass goes into growth

Working: In warm surroundings less energy is transferred to the environment, so more food becomes body tissue.

Question 2. True or false? Limiting the movement of farm animals means less glucose is respired for muscle contraction.

Answer: True

Working: True. More of their food can then be used for growth.

Question 3. Indoor chickens need 1.8 kg of feed per kg of mass gained. 2000 chickens each gain 2 kg. How much feed is needed?

Answer: 7200 kg

Working: 2000 × 2 = 4000 kg gained. 4000 × 1.8 = 7200 kg of feed.

Related lessons

• Previous lesson: 18.10 Factors Affecting Food Security
• Next lesson: 18.12 Sustainable Food Production
• In this chapter: 18.1 The Human Population Explosion
• In this chapter: 18.2 Land and Water Pollution
• In this chapter: 18.3 Air Pollution

Continue in the full course

This lesson is section 18.11 (AGCBH1811) of our free GCSE Biology course for AQA. In the full course you get every video for this section, a self-marking practice quiz, a printable worksheet with a mark scheme, chapter tests, and your progress saved. Go to the full GCSE Biology course.