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How intensive rearing of domestic livestock increases the efficiency of energy conversion
Transcript of How intensive rearing of domestic livestock increases the efficiency of energy conversion
Intensive rearing of livestock is designed to produce the maximum yield of produce - meat, eggs and milk - at the lowest possible cost. Cows, pigs, chickens and turkeys are the animals most commonly reared intensively.
Livestock - farm animals raised for home use or for profit
Rearing - how the animals are raised/cared for
Yield - the amount of produce Intensive rearing and energy conversion
As energy passes along a food chain only a small percentage passes from one organism in the chain to the next because much of the energy is lost as heat in respiration. Decomposers and detritivores (feeding on faeces, urine and dead organisms) Sun 1-3% Primary
producers 5-10% Primary
Consumers 15-20% Secondary
Consumers 15-20% Tertiary
Consumers Energy lost as heat during respiration Energy lost as
reflected light Intensive rearing of domestic livestock is about converting the smallest possible amount of food energy into the greatest quality of animal mass.
This can be achieved by;
minimising energy losses from domestic animals during their lifetime. Meaning more of the food energy taken in by the animals will be converted into body mass, ready to be passed on to the next link in the food chain - us. How to make energy conversion more efficient
Ensure that as much energy from respiration as possible goes into growth rather than activities or other organisms. So, how do they do this?
By keeping animals in confined spaces such as small enclosures, barns or cages e.g. 'factory farming' This increases the energy conversion rate because:
movement is restricted and so less energy is used in muscle contraction,
the environment can be kept warm in order to reduce heat loss from the body,
feeding can be controlled so that animals receive the optimum amount and type of food for maximum growth with no wastage,
predators are excluded so that there is no loss to other organisms in the food web. Other means of improving the energy-conversion rate include:
selective breeding of animals to produce the varieties that are more efficient at converting the food they eat into body mass,
using hormones to increase growth rate. Answer summary questions on page 80 A 1) Movement is restricted so less energy is expended in muscle contraction/ heat loss is reduced so less energy is expended maintaining body temperature/ the optimum amount and type of food for rapid growth can be provided/ predators are excluded so no energy is lost to other organisms.
A 2) A longer darker period means more time is spent resting, less energy is expended, and more energy is converted into body mass. A 2) For Against Efficient energy conversion
Economic - makes good use of resources
Less land required/more land for natural habitats
Safer/more easily regulated farms
Disease/predators more easily excluded
Animals are warm and well fed Lower quality eggs/less taste
Disease spreads more rapidly
Antibiotic resistance - can spread to human disease - causing bacteria
Hens kept unnaturally - may be stressed or aggressive and therefore need to be de-beaked
Restricted movement means more osteoporosis/joint pain
More pollution/smells/harmful to environment
Use of fossil fuels means more CO2/global warming A 3) Any balanced discussion of issues such as: crowded, confined conditions versus being warm, fed, kept healthy, free from predators/ need for drugs versus becoming diseased/ de-beaking versus harming one another/ keeping animals unnaturally versus our demand for cheap food/ treating animals badly (osteoporosis, boredom, frustration) versus animal welfare legislation to prevent cruelty.