6 LEAFLET 233, U. S. DEPARTMENT OF AGRICULTURE 
Efficient, | Rapid Growth 
Efficient, rapid growth is best measured by the weight of the bird 
at an early age. Statistical studies’ on the growth of cockerels 
N—3880 
Figure 7.—Chicks showing contrasting feather growth. Left, slow-feathering 
chick at age of 10 days; right, fast-feathering chick at same age. 
have indicated that the greatest variability occurs between 3 and 6 
weeks of age, if a good diet is fed and the cockerels have access to 
direct sunight and free range. Therefore, this is the best period in 
which to make accurate selection of the most efficient birds by their 
body weights. At this age there are maximum differences in weight 
between the slowest growing, the average, and the fastest growing 
individuals. This difference becomes less and less after the fourth 
week, until at maturity there is approximately no difference. Thus, 
the older the birds after 4 weeks of age, the less accurately can selec- 
tion be made on the basis of efficiency of growth. 
Some of the best birds selected at this time, however, do not 
develop up to expectations; others appear to stop growing at an early 
| HAMMOND, J. C., and Brrp, H. R. EFFECTS OF NUTRITION ON VARIABILITY IN THE GROWTH OF 
CHICKENS. Poultry Sci. 21: 230-242, illus. 1942. 
