Access

You are not currently logged in.

Access JSTOR through your library or other institution:

login

Log in through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Journal Article

Metabolic and Digestive Responses to Artificial Selection in Chickens

Sue Jackson and Jared Diamond
Evolution
Vol. 50, No. 4 (Aug., 1996), pp. 1638-1650
DOI: 10.2307/2410900
Stable URL: http://www.jstor.org/stable/2410900
Page Count: 13
  • Read Online (Free)
  • Download ($4.00)
  • Subscribe ($19.50)
  • Add to My Lists
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Metabolic and Digestive Responses to Artificial Selection in Chickens
Preview not available

Abstract

Compared to ancestral wild jungle fowl, domestic broiler chickens have been consciously selected for large body size, relatively large pectoral muscles, rapid growth, and high feed efficiency. Hence intraspecific comparisons of these two strains could help identify consequences of unconscious artificial selection, trade-offs an energy allocation, and factors limiting energy budgets. We therefore compared our measurements of many corresponding parameters in both strains: growth rate, energy intake, digestive efficiency, metabolic rate and its components, organ masses, and intestinal brush-border nutrient transporter and hydrolase activities and capacities, as functions of age and body mass in zero- to nine-week-old chicks. Both strains prove to have the same digestive efficiency Compared to equal-sized jungle fowl, broilers have higher daily energy intake and activity costs. Broilers have relatively longer and wider, hence heavier, small intestines, and their other gut compartments are also relatively larger. Offsetting these increases, broilers have relatively smaller brains and leg bones, these being much less important to a captive bird than to a wild bird exposed to predators. Broilers have generally lower intestinal transporter activities, but relatively higher transporter capacities because of their larger guts. Among domestic chicken strains, comparison of broilers with layers, the former having been consciously selected for much higher growth rates, yields generally similar conclusions. Thus, as recognized in broad outline by Darwin, domestication provides clear examples of conscious selection, of unconscious selection for traits prerequisite to the consciously selected traits, and of unconscious selection against traits rendered less important or competing for space or energy.

Page Thumbnails

  • Thumbnail: Page 
1638
    1638
  • Thumbnail: Page 
1639
    1639
  • Thumbnail: Page 
1640
    1640
  • Thumbnail: Page 
1641
    1641
  • Thumbnail: Page 
1642
    1642
  • Thumbnail: Page 
1643
    1643
  • Thumbnail: Page 
1644
    1644
  • Thumbnail: Page 
1645
    1645
  • Thumbnail: Page 
1646
    1646
  • Thumbnail: Page 
1647
    1647
  • Thumbnail: Page 
1648
    1648
  • Thumbnail: Page 
1649
    1649
  • Thumbnail: Page 
1650
    1650