SeedCo trial fields are used for breeding seeds. Image credit

SeedCo trial fields are used for breeding seeds. Image credit

ZIMSEC O Level Combined Science Notes: Breeding

  • Controlled breeding in livestock and crops allow farmers to obtain animals and crops with the best characteristics
  • Each breed or variety has is own characteristics for example with cattle some breeds are good for meat and others produce more milk
  • With chickens some breeds (broilers) are bred for meat and other breeds to lay eggs
  • If a group of animals are allowed to breed freely without any new animals that group becomes less productive
  • Undesirable characteristics such as deformities and reduced resistance to diseases will increased
  • In-breeding-is when no new individuals are introduced to a herd/group of animals
  • This results in reduced variation and thus natural selection and adaptation are negatively impacted
  • Farmers cross-breed to maintain variety in their herds
  • Cross-breedingis the process of introducing new animals with desirable characteristics into a herd so that variation is maintained
  • Farmers choose the characteristics they need and want for their local conditions and their productivity and set up a breeding programme

In cattle

  • For example local breeds of cattle such as the Mashona and the Afrikaner are well suited to the local conditions in Zimbabwe
  • These breeds are cross-bred with imported breeds such as the Aberdeen and Hereford breeds so as to increase meat and milk productivity
  • This is done using artificial insemination where sperm from the foreign breeds is inseminated into a local cow

In crops

  • Different maize crops are also produced using cross-breeding
  • Crop strains such as those that are resistant to diseases such as Grey Leaf Spot are bred with those that have a high yield
  • Crops are also bred so as to be drought resistant, have a shorter time to maturity etc
  • Crops can also be bred so as to suit local climatic conditions
  • Research workers constantly experiment with different cross-bred varieties in order to improve the suitability of the crops

To access more topics go to the Combined Science Notes page.

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