The Influence of Sire, Dam, and Hatching Date on Specific Rate of Growth of Single Comb White Leghorn Pullets from Hatching to Twelve Weeks of Age

IN 1948 a study was begun to ascertain, among other things, the effects of sire differences, dam differences, and date-of-hatch differences on variation in growth of standard-bred Single Comb White Leghorn pullets from hatching to 12 weeks of age. Three general methods for evaluating growth of an individual animal have been used: (1) cumulative weights, (2) successive gains (specific rates of growth), and (3) relative rates of growth (some transformation of weight or gain, usually logarithmic). There is a considerable amount of literature dealing with the advantages of one method over another in graphic and statistical studies of growth of populations as well as individuals. However, in this paper interest is centered on specific rate of growth because successive gains are additive without the necessity of a logarithmic transformation. While it is known that environmental factors such as temperature and ration affect growth (Moulton, Kempster, Hogan and Brody, 1923), few . . .