Am. Soc. Anim. Prod.
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Am. Soc. Anim. Prod. 1937:296-306
© 1937 American Society of Animal Science
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The Relation of Type and Time of Birth and Birth Weight of Lambs to their Survival, Growth and Suitability for Breeding

Ralph W. Phillips and W. M. Dawson

United States Department of Agriculture

Abstract

Data have been presented on 829 Southdown lambs showing that:

  1. Single lambs are heavier than twins at three months of age.
  2. Lambs that are heavier at birth also tend to be heavier at three months of age.
  3. Lambs born early in the season are heavier at three months of age than late lambs.
  4. Differences in weight at one year due to birth factors are too small to be statistically significant. One exception is the difference between single and twin female lambs.
  5. Twin lambs survive equally as well as singles to three months of age.
  6. Early male lambs survive better than late ones. The difference between the early and late female lambs is in the same direction but is too small to be significant.
  7. Male lambs that are heavy at birth survive better than light ones. A higher percent of the heavy females survive, also, but the difference is not statistically significant.
  8. In the selection of breeding animals single lambs are favored over twins, early lambs over late, and lambs heavy at birth over light ones, even though no conscious effort has been made to favor any of these groups.

The effects of type of birth, birth weight and birth date on the phenotypic selection of breeding animals are discussed and suggestions are made for overcoming some of the weaknesses of the method now in use.






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Copyright © 1937 by the American Society of Animal Science.