section_path: Animal growth and development/Genetics
section_name: Genetics
paragraph_text: Genetics
  
  Some economically important traits in meat animals are heritable to some degree, and can thus be selected for by animal breeding. In cattle, certain growth features are controlled by recessive genes which have not so far been controlled, complicating breeding. One such trait is dwarfism; another is the doppelender or " double muscling " condition, which causes muscle hypertrophy and thereby increases the animal's commercial value. Genetic analysis continues to reveal the genetic mechanisms that control numerous aspects of the endocrine system and, through it, meat growth and quality.
  
  Genetic engineering techniques can shorten breeding programs significantly because they allow for the identification and isolation of genes coding for desired traits, and for the reincorporation of these genes into the animal genome. To enable such manipulation, the genomes of many animals are being mapped. Some research has already seen commercial application. For instance, a recombinant bacterium has been developed which improves the digestion of grass in the rumen of cattle, and some specific features of muscle fibers have been genetically altered. Experimental reproductive cloning of commercially important meat animals such as sheep, pig or cattle has been successful. Multiple asexual reproduction of animals bearing desirable traits is anticipated.